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Rifampicin
Selected AbstractsModulation of sinusoidal and canalicular elimination of bilirubin-glucuronides by rifampicin and other cholestatic drugs in a sandwich culture of rat hepatocytesHEPATOLOGY RESEARCH, Issue 3 2008György Lengyel Aim:, Drug-induced hyperbilirubinemia has been shown to often be derived from modulation of the expression and activity of hepatobiliary transporters. In this study we examined the interactions of some therapeutic agents, which have been shown to cause cholestasis, with the elimination of bilirubin-glucuronides, in order to clarify whether these drugs modify the activity of Mrp2 and Mrp3 directly. Methods:, The modulation of bilirubin-glucuronide elimination with rifampicin, probenecid, indomethacin and benzbromarone was assayed in sandwich cultured rat hepatocytes. Results:, All the drugs studied decreased the canalicular transport, but modified the sinusoidal efflux differently. Rifampicin and probenecid stimulated the sinusoidal efflux, shifting the elimination of bilirubin-glucuronides to the sinusoidal domain (biliary excretion index: 3.9 ± 1.2; 22.7 ± 7.4 vs. 56.6 ± 1.5 and 56.8 ± 5.5). However, the overall elimination of bilirubin-glucuronides did not change significantly. In contrast, indomethacin and benzbromarone inhibited bothtransport processes, resulting in the decrease of the overall bilirubin-glucuronide elimination (61 ± 22; 56 ± 5% of the control). Rifampicin, indomethacin and benzbromarone decreased 5,(6)-carboxy-2,,7,-dichlorofluorescein transport by multidrug resistance-associated protein (Mrp)2 as visualized by confocal laser microscopy and in vesicular transport experiments. Interestingly, rifampicin decreased the MRP3 activity in vesicular transport experiments using 17-beta-estradiol-17-beta-D-glucuronide as substrate, in contrast to that observed in bilirubin-glucuronide transport experiments. Conclusion:, Here we show that the interactions of drugs on hepatobiliary transporter proteins may be identified in vitro in a sandwich culture of hepatocytes, in which canalicular and sinusoidal transport can be studied separately. [source] Application of the biodegradable diblock copolymer poly(L -lactide)- block -poly(L -cysteine): Drug delivery and protein conjugationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jing Sun Abstract A novel approach to self-assembled and shell-crosslinked (SCL) micelles from the diblock copolymer poly(L -lactide)- block -poly(L -cysteine) to be used as drug and protein delivery carriers is described. Rifampicin was used as a model drug. The drug-loaded SCL micelles were obtained by self-assembly of the copolymer in the presence of the drug in aqueous media. Their morphology and size were studied with dynamic light scattering and field emission scanning electron microscopy. The rifampicin loading capacity and encapsulation efficiency were studied with ultraviolet,visible spectrophotometry. The drug-release rate in vitro depended on the oxidizing and reducing environment. Moreover, a straightforward approach to the conjugation of the copolymer with bovine serum albumin (BSA) was developed, and a gel electrophoresis test demonstrated that this conjugated BSA could be reversibly released from the copolymer substrate under reducing conditions. In conclusion, this L -cysteine copolymer can be used in drug delivery and in protein fixation and recovery. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Surface-enhanced resonance Raman spectroscopy of rifamycins on silver nanoparticles: insight into their adsorption mechanismsJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2006Barry D. Howes Abstract Three widely used antibiotics from the rifamycin family, rifamycin SV sodium salt, rifampicin and rifaximin, have been characterized by resonance Raman (RR) and surface-enhanced resonance Raman spectroscopy (SERRS). SERRS spectra were recorded using aqueous silver colloidal dispersions prepared with two reducing agents, sodium borohydride and hydroxylamine hydrochloride, for a range of pH values to identify the SERRS-active substrate surface most suitable for each of the three antibiotics. Rifampicin was found to give intense SERRS signals only for the borohydride-reduced colloid and only at pH < 7.7, whereas the hydroxylamine HCl-reduced colloid was the best substrate for rifaximin, giving considerably more intense SERRS spectra than the borohydride colloid. SERRS spectra of rifaximin were observed only at pH < 7.0. It is proposed that the marked pH dependence of the SERRS enhancement results from a transition from an anionic to a neutral zwitterionic state. SERRS spectra of rifamycin SV were not observed for any experimental conditions. The antibiotics display remarkably contrasting SERRS behaviour, reflecting differences in the nature of the substituent groups on the chromophore ring. A vibrational assignment of the RR spectra and detailed comparison between the RR and SERRS data have given insight into the mechanism of adsorption of the antibiotics onto the Ag surface. Rifampicin and rifaximin adsorb adopting an approximately similar vertical orientation of the chromophore ring with respect to the surface; however, rifampicin adsorbs by direct chemical interaction with the Ag whereas rifaximin does not form a direct bond with the Ag surface. Copyright © 2006 John Wiley & Sons, Ltd. [source] Metabolism of Repaglinide by CYP2C8 and CYP3A4 in vitro: Effect of Fibrates and RifampicinBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 4 2005Lauri I. Kajosaari To clarify the mechanisms of observed repaglinide drug interactions, we determined the contribution of the two enzymes to repaglinide metabolism at different substrate concentrations, and examined the effect of fibrates and rifampicin on CYP2C8, CYP3A4 and repaglinide metabolism in vitro. We studied repaglinide metabolism using pooled human liver microsomes, recombinant CYP2C8 and recombinant CYP3A4 enzymes. The effect of quercetin and itraconazole on repaglinide metabolism, and of gemfibrozil, bezafibrate, fenofibrate and rifampicin on CYP2C8 (paclitaxel 6,-hydroxylation) and CYP3A4 (midazolam 1-hydroxylation) activities and repaglinide metabolism were studied using human liver microsomes. At therapeutic repaglinide concentrations (<0.4 ,M), CYP2C8 and CYP3A4 metabolised repaglinide at similar rates. Quercetin (25 ,M) and itraconazole (3 ,M) inhibited the metabolism of 0.2 ,M repaglinide by 58% and 71%, and that of 2 ,M repaglinide by 56% and 59%, respectively. The three fibrates inhibited CYP2C8 (Ki: bezafibrate 9.7 ,M, gemfibrozil 30.4 ,M and fenofibrate 92.6 ,M) and repaglinide metabolism (IC50: bezafibrate 37.7 ,M, gemfibrozil 111 ,M and fenofibrate 164 ,M), but had no effect on CYP3A4. Rifampicin inhibited CYP2C8 (Ki 30.2 ,M), CYP3A4 (Ki 18.5 ,M) and repaglinide metabolism (IC50 13.7 ,M). In conclusion, both CYP2C8 and CYP3A4 are important in the metabolism of therapeutic concentrations of repaglinide in vitro, but their predicted contributions in vivo are highly dependent on the scaling factor used. Gemfibrozil is only a moderate inhibitor of CYP2C8 and does not inhibit CYP3A4; inhibition of CYP-enzymes by parent gemfibrozil alone does not explain its interaction with repaglinide in vivo. Rifampicin competitively inhibits both CYP2C8 and CYP3A4, which can counteract its inducing effect in humans. [source] Inhibition of Amyloid Fibrillization of Hen Egg-White Lysozymes by Rifampicin and p -BenzoquinoneBIOTECHNOLOGY PROGRESS, Issue 3 2007Valerie H. Lieu It has been reported that more than 20 different human proteins can fold abnormally, resulting in the formation of pathological deposits and several lethal degenerative diseases. Despite extensive investigations on amyloid fibril formation, the detailed molecular mechanism remained rather elusive. The current research, utilizing hen egg-white lysozymes as a model system, is aimed at exploring inhibitory activities of two potential molecules against lysozyme fibril formation. We first demonstrated that the formation of lysozyme amyloid fibrils at pH 2.0 was markedly enhanced by the presence of agitation in comparison with its quiescent counterpart. Next, via numerous spectroscopic techniques and transmission electron microscopy, our results revealed that the inhibition of lysozyme amyloid formation by either rifampicin or its analogue p -benzoquinone followed a concentration-dependent fashion. Furthermore, while both inhibitors were shown to acquire an anti-aggregating and a disaggregating activity, rifampicin, in comparison with p -benzoquinone, served as a more effective inhibitor against in vitro amyloid fibrillogenesis of lysozyme. It is our belief that the data reported in this work will not only reinforce the findings validated by others that rifampicin and p -benzoquinone serve as two promising preventive molecules against amyloid fibrillogenesis, but also shed light on a rational design of effective therapeutics for amyloidogenic diseases. [source] Rifampicin exacerbates isoniazid-induced toxicity in human but not in rat hepatocytes in tissue-like culturesBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2008C Shen Background and purpose: Rifampicin has been extensively reported to exacerbate the hepatotoxicity of isoniazid in patients with tuberculosis. However, this was controversially claimed by previous reports using rat models. This study evaluated the effect of rifampicin on isoniazid-induced hepatocyte toxicity by using human and rat hepatocytes in tissue-like culture. Experimental approach: Hepatocytes in tissue-like gel entrapment were used to examine isoniazid toxicity, as shown by cell viability, intracellular glutathione content and albumin secretion. For demonstration of the differential effects of rifampicin on human and rat hepatocytes, induction by rifampicin of cytochrome P450 (CYP) 2E1, a major enzyme associated with isoniazid hepatotoxicity, was detected by 4-nitrocatechol formation and RT-PCR analysis. Key results: Rifampicin (12 ,M) enhanced isoniazid-induced toxicity in human hepatocytes but not in rat hepatocytes. Enhanced CYP 2E1 enzymic activity and mRNA expression were similarly detected in human hepatocytes but not in rat hepatocytes. Both rat and human hepatocytes in gel entrapment were more sensitive to isoniazid treatment compared with the corresponding hepatocytes in a monolayer culture. Conclusions and implications: The difference in induction of CYP 2E1 by rifampicin between rat and human hepatocytes accounted for the difference in exacerbation of isoniazid hepatocyte toxicity by rifampicin, with more significant toxicity in gel entrapment than in monolayer cultures. Thus, human hepatocytes in tissue-like cultures (gel entrapment) could be an effective model for hepatotoxicity research in vitro, closer to the in vivo situation. British Journal of Pharmacology (2008) 153, 784,791; doi:10.1038/sj.bjp.0707611; published online 10 December 2007 [source] Adsorptive Stripping Voltammetry of Rifamycins at Unmodified and Surfactant-Modified Carbon Paste ElectrodesELECTROANALYSIS, Issue 20 2004Sonia Gutiérrez-Fernández Abstract The electrochemical behavior of the antibiotics rifampicin and rifamycin SV is investigated by cyclic voltammetry at carbon paste and in situ surfactant modified carbon paste electrodes. Both antibiotics adsorb on the unmodified electrodes and show a reversible redox process due to the oxidation of the 6,9-dihydroxynaphthalene moiety to the corresponding naphthoquinone. This process is used as analytical signal for developing adsorptive voltammetric methods for the determination of the antibiotics. Experimental parameters, such as pH of the supporting electrolyte, accumulation potential and time are optimized. After accumulation from acidic solutions (0.1,M KCl pH 2 or HCl 0.2,M) at ,0.1 or 0,V for 3,min, the differential pulse oxidation peak current changes linearly with the antibiotic concentration in the range 3.5×10,10,M ,5.4×10,9,M or 5×10,11,M ,1.0×10,9,M for rifampicin and rifamycin SV, respectively. Rifamycin SV is not accumulated on carbon paste electrodes modified in situ with the anionic surfactant sodium dodecyl sulfate, whereas rifampicin is readily accumulated on this modified electrodes resulting in a signal enhancement and allowing rifampicin determinations without interference from rifamycin SV. On the other hand, selective determination of rifamycin SV in the presence of rifampicin is achieved by using carbon paste electrodes in situ modified with the cationic surfactant cetyltrimethylammonium chloride. [source] Development of a bacterial challenge test for gnotobiotic sea bass (Dicentrarchus labrax) larvaeENVIRONMENTAL MICROBIOLOGY, Issue 2 2009K. Dierckens Summary The use of probiotic microorganisms in aquaculture is gaining a lot of interest. Gnotobiotic model systems are required in order to fully understand the effects and modes-of-action of these microorganisms, as the native microbial communities present in non-sterile animals can lead to false conclusions. In this study, a gnotobiotic sea bass larvae (Dicentrarchus labrax) test system was developed. In order to obtain bacteria-free animals, the eggs were disinfected with glutaraldehyde and subsequently incubated in a solution of rifampicin and ampicillin. Axenity was confirmed using culture-dependent and -independent techniques. The gnotobiotic larvae were fed axenic Artemia sp. from 7 days after hatching onwards. In the challenge test, one of the three opportunistic pathogens, Aeromonas hydrophila, Listonella anguillarum serovar O1 and O2a, was added to the model system via the water and encapsulated in Artemia sp. Only serovar O2a led to increased mortality in the sea bass larvae. The presented gnotobiotic model can be used for research on, among others, reciprocal metabolic effects between microorganisms and the host (e.g. as measured by gene expression), immunostimulants, pharmacological research and the histological development of the gastrointestinal tract and growth of larvae. [source] Dose-dependent Induction of Cytochrome P450 (CYP) 3A4 and Activation of Pregnane X Receptor by TopiramateEPILEPSIA, Issue 12 2003Srikanth C. Nallani Summary:,Purpose: In clinical studies, topiramate (TPM) was shown to cause a dose-dependent increase in the clearance of ethinyl estradiol. We hypothesized that this interaction results from induction of hepatic cytochrome P450 (CYP) 3A4 by TPM. Accordingly, we investigated whether TPM induces CYP3A4 in primary human hepatocytes and activates the human pregnane X receptor (hPXR), a nuclear receptor that serves as a regulator of CYP3A4 transcription. Methods: Human hepatocytes were treated for 72 h with TPM (10, 25, 50, 100, 250, and 500 ,M) and known inducers, phenobarbital (PB; 2 mM), and rifampicin (10 ,M). The rate of testosterone 6,-hydroxylation by hepatocytes served as a marker for CYP3A4 activity. The CYP3A4-specific protein and mRNA levels were determined by using Western and Northern blot analyses, respectively. The hPXR activation was assessed with cell-based reporter gene assay. Results: Compared with controls, TPM (50,500 ,M),treated hepatocytes exhibited a considerable increase in the CYP3A4 activity (1. 6- to 8.2-fold), protein levels (4.6- to 17.3-fold), and mRNA levels (1.9- to 13.3-fold). Comparatively, rifampicin (10 ,M) effected 14.5-, 25.3-, and a 20.3-fold increase in CYP3A4 activity, immunoreactive protein levels, and mRNA levels, respectively. TPM (50,500 ,M) caused 1.3- to 3-fold activation of the hPXR, whereas rifampicin (10 ,M) caused a 6-fold activation. Conclusions: The observed induction of CYP3A4 by TPM, especially at the higher concentrations, provides a potential mechanistic explanation of the reported increase in the ethinyl estradiol clearance by TPM. It also is suggestive of other potential interactions when high-dose TPM therapy is used. [source] Extensively drug-resistant tuberculosis: current challenges and threatsFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2008Amita Jain Abstract Extensively drug-resistant tuberculosis (XDR-TB) is defined as tuberculosis caused by a Mycobacterium tuberculosis strain that is resistant to at least rifampicin and isoniazid among the first-line antitubercular drugs (multidrug-resistant tuberculosis; MDR-TB) in addition to resistance to any fluroquinolones and at least one of three injectable second-line drugs, namely amikacin, kanamycin and/or capreomycin. Recent studies have described XDR-TB strains from all continents. Worldwide prevalence of XDR-TB is estimated to be c. 6.6% in all the studied countries among multidrug-resistant M. tuberculosis strains. The emergence of XDR-TB strains is a reflection of poor tuberculosis management, and controlling its emergence constitutes an urgent global health reality and a challenge to tuberculosis control activities in all parts of the world, especially in developing countries and those lacking resources and as well as in countries with increasing prevalence of HIV/AIDS. [source] Induction of CspA, an E. coli major cold-shock protein, upon nutritional upshift at 37,°CGENES TO CELLS, Issue 4 2001Kunitoshi Yamanaka Background The synthesis of CspA, the major cold-shock protein of Escherichia coli, is dramatically induced upon cold shock. It was recently reported that there is massive presence of CspA under nonstress conditions, and it is thus claimed that CspA as the cold-shock protein is a misnomer. Results Here, we re-examined and confirmed that CspA is induced upon culture dilution at 37 °C. However, its induction level is one-sixth of the cold-shock-induced level, clearly indicating that the major stress that induces CspA is cold shock. It was further found that CspA induction can be achieved not only by culture dilution but also by the simple addition of nutrients, and that it was almost completely abolished in the presence of rifampicin or nalidixic acid. Nutritional upshift causes the induction of only CspA but not other cold-shock-inducible CspA homologues. The amount of cspA mRNA rapidly and transiently increased by culture dilution, but its stability was not significantly changed. Conclusions These results suggest that CspA is a nutritional-upshift stress protein as well as a cold-shock stress protein, and that CspA induction following nutritional upshift may be due to transcriptional activation. [source] Association of a single nucleotide polymorphism in the steroid and xenobiotic receptor (SXR) gene (IVS1-579A/G) with bone mineral densityGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 2 2007Tomohiko Urano Vitamin K2 plays an important role in the bone metabolism. The steroid and xenobiotic receptor (SXR) as a nuclear receptor activated by vitamin K2 as well as rifampicin could increase bone markers such as alkaline phosphatase in human osteoblastic cells. Thus, the SXR could mediate vitamin K2 signaling pathway in bone cells. Therefore, we analyzed expression of the SXR mRNA in human primary osteoblasts and chondrocytes. We also studied association of a single nucleotide polymorphism (SNP) in the SXR gene with bone mineral density (BMD). Expression levels of the SXR mRNA were analyzed during the culture course of human primary osteoblasts and chondrocytes. Association of a SNP in the SXR gene in intron 1 (IVS1-579A>G) with BMD was examined in 294 healthy postmenopausal Japanese women. The SXR mRNA increased at day 5 and then decreased at day 10 in human primary osteoblasts. Its mRNA gradually increased in human primary chondrocytes until day 10. As an association study of a SNP in the SXR gene (IVS1-579A/G), the subjects without the A allele (GG; n = 47) had significantly higher total BMD than the subjects bearing at least one A allele (AA + AG; n = 247) (Z score ± SD; 0.635 ± 1.031 versus 0.268 ± 1.061; P = 0.0298). The SXR mRNA was expressed and regulated in primary human osteoblasts and chondrocytes. A genetic variation at the SXR gene locus is associated with BMD, suggesting an involvement of the SXR gene in human bone metabolism. [source] High Level of Antimicrobial Resistance in French Helicobacter pylori IsolatesHELICOBACTER, Issue 1 2010Josette Raymond Abstract Background: Helicobacter pylori is a human pathogen responsible for serious diseases including peptic ulcer disease and gastric cancer. The recommended triple therapy included clarithromycin but increasing resistance has undermined its effectiveness. It is therefore important to be aware of the local prevalence of antimicrobial resistance to adjust treatment strategy. Materials and Methods: Overall, 530 biopsies were collected between 2004 and 2007. The antimicrobial susceptibility of H. pylori was determined by E-test and molecular methods. Results: Among these, 138/530 (26%) strains were resistant to clarithromycin, 324/530 (61%) to metronidazole and 70/530 (13.2%) to ciprofloxacin. Whereas no resistance against amoxicillin and tetracycline was observed, only one strain was resistant to rifampicin. Compared to the patients never treated for H. pylori infection, the prevalence of resistance was significantly higher in patients previously treated (19.1% vs 68% for clarithromycin; 13.2% vs 53.3% for both clarithromycin and metronidazole). The trend analysis revealed an increase of primary resistance to ciprofloxacin between 2004 and 2005 (7.3%) vs 2006,2007 (14.1%) (p = .04) and the secondary resistance reached 22.7% in 2007. Interestingly, 27 biopsies (19.6%) contained a double population of clarithromycin-susceptible and -resistant strains. Conclusions: The reported high prevalence of clarithromycin and multiple resistances of H. pylori suggest that the empiric therapy with clarithromycin should be abandoned as no longer pretreatment susceptibility testing has assessed the susceptibility of the strain. As culture and antibiogram are not routinely performable in most clinical laboratories, the use of molecular test should be developed to allow a wide availability of pretreatment susceptibility testing. [source] Modulation of sinusoidal and canalicular elimination of bilirubin-glucuronides by rifampicin and other cholestatic drugs in a sandwich culture of rat hepatocytesHEPATOLOGY RESEARCH, Issue 3 2008György Lengyel Aim:, Drug-induced hyperbilirubinemia has been shown to often be derived from modulation of the expression and activity of hepatobiliary transporters. In this study we examined the interactions of some therapeutic agents, which have been shown to cause cholestasis, with the elimination of bilirubin-glucuronides, in order to clarify whether these drugs modify the activity of Mrp2 and Mrp3 directly. Methods:, The modulation of bilirubin-glucuronide elimination with rifampicin, probenecid, indomethacin and benzbromarone was assayed in sandwich cultured rat hepatocytes. Results:, All the drugs studied decreased the canalicular transport, but modified the sinusoidal efflux differently. Rifampicin and probenecid stimulated the sinusoidal efflux, shifting the elimination of bilirubin-glucuronides to the sinusoidal domain (biliary excretion index: 3.9 ± 1.2; 22.7 ± 7.4 vs. 56.6 ± 1.5 and 56.8 ± 5.5). However, the overall elimination of bilirubin-glucuronides did not change significantly. In contrast, indomethacin and benzbromarone inhibited bothtransport processes, resulting in the decrease of the overall bilirubin-glucuronide elimination (61 ± 22; 56 ± 5% of the control). Rifampicin, indomethacin and benzbromarone decreased 5,(6)-carboxy-2,,7,-dichlorofluorescein transport by multidrug resistance-associated protein (Mrp)2 as visualized by confocal laser microscopy and in vesicular transport experiments. Interestingly, rifampicin decreased the MRP3 activity in vesicular transport experiments using 17-beta-estradiol-17-beta-D-glucuronide as substrate, in contrast to that observed in bilirubin-glucuronide transport experiments. Conclusion:, Here we show that the interactions of drugs on hepatobiliary transporter proteins may be identified in vitro in a sandwich culture of hepatocytes, in which canalicular and sinusoidal transport can be studied separately. [source] Potentiation of isoniazid-induced liver toxicity by rifampicin in a combinational therapy of antitubercular drugs (rifampicin, isoniazid and pyrazinamide) in Wistar rats: A toxicity profile studyHEPATOLOGY RESEARCH, Issue 10 2007Sheikh Abdullah Tasduq Aim:, Biochemical characterization of long-term toxic manifestations of anti-tubercular (anti-TB) drugs , rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA) , individually and in two combinations: (i) RIF + INH, and (ii) RIF + INH + PZA in Wistar rats. Methods:, Animals received anti-TB drugs , alone or in combination , once daily p.o. for up to 90 days (doses, in mg/kg: RIF, 250; INH, 50; PZA, 100). Assays for alanine aminotransferase (ALT), alkaline phosphatase (ALP), bilirubin (serum) and lipid peroxidation (LPO), glutathione (GSH), glutathione peroxidase (GPx), catalase, Na+K+-ATPase and CYP 2E1 (liver) were performed to assess liver toxicity. Clinical biochemistry was done by commercial kits. Determinations were made at 0, 15, 30 and 90 days of treatment schedule. Results:, Anti-TB drugs-treated animals showed abnormal rises or falls (>1.5,2 fold) in the serum/liver parameters. Mild hyperlipidemia, hypercholesterolemia and hyperuricemia were the other pathologies. Of all the treated groups, INHalone or in combination with other drugs produced a progressive enhancement of toxicity over 15,90 days. The in vivo results were further supported by in vitro results (MTT assay, GSH and LPO) in primary cultures of rat hepatocyte. Results indicated that anti-TB drugs in combination: (i) caused membrane damage resulting in leakage of ALT, ALP and bilirubin; (ii) caused imbalance in endogenous enzymatic oxidant,antioxidant defense via increased lipid peroxidation and in glutathione homeostasis; and (iii) enhanced the CYP 2E1-mediated bioactivation mechanism. Conclusion:, Toxicity manifestations seemed to be heptocytic injury targeted at hepatocytes, bile ducts or sinusoidal cells related to hepatitis and primary biliary cholestasis. [source] THE ROLE OF BACTERIAL SYMBIONTS IN AMINO ACID COMPOSITION OF BLACK BEAN APHIDSINSECT SCIENCE, Issue 3 2003Xue-xia Miao Abstract To evaluate the role of bacterial symbionts (Buchnera spp.) in the black bean aphids (Aphis craccivora Koch), the aphids were treated with the antibiotic, rifampicin, to eliminate their intracellular symbiotic bacteria. Analysis of protein and amino acid concentration in 7-day-old of aposymbiotic aphids showed that the total protein content per mg fresh weight was significantly reduced by 29%, but free amino acid titers were increased by 17%. The ratio of the essential amino acids was in general only around 20% essential amino acids in phloem sap of broad bean, whereas it was 44% and 37% in symbiotic and aposymbiotic aphids, respectively, suggesting that the composition of the free amino acids was unbalanced. For example, the essential amino acid, threonine represented 21.6% of essential amino acids in symbiotic aphids, but it was only 16.7% in aposymbiotic aphids. Likewise, two nonessential amino acids, tyrosine and serine, represented 8.9% and 5.6% of total amino acids in symbiontic aphids, respectively, but they enhanced to 21.1% and 13.6% in aposymbiotic aphids. It seems likely that the elevated free amino acid concentration in aposymbiotic aphids was caused by the limited protein anabolism as the result of the unbalanced amino acid composition. [source] Tuberculosis verrucosa cutis: antitubercular therapy, a well-conceived diagnostic criterionINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 3 2005Virendra N. Sehgal MD A 39-year-old housewife sustained inadvertent trauma to the right index finger about 6 years ago, whilst stitching clothes. A couple of weeks later, the site of trauma became hard and gritty. Ever since, it has progressed slowly, without any appreciable outward sign. It was not associated with any discomfort/pain. Consequent on an opinion from a surgeon, it was decided to operate on the right index finger. During the operation, under local anesthesia, a hard and gritty material was removed. The material was subjected to histopathologic study. Several stitches were applied to the wound. It failed to respond to antimicrobial therapy over a 4-week period, prompting the patient to seek another opinion. Examination of the skin surface revealed a plaque with an irregular configuration on and around the distal interphalangeal joint of the right index finger. It was erythematous and pigmented. The top of the plaque was irregular and had alternating elevations and depressions (Fig. 1). Diascopy was negative for apple jelly nodule. A bacillus Calmette,Guérin (BCG) vaccination scar was identified on the left deltoid. There was no regional lymphadenopathy or systemic abnormality. Mantoux test with intradermal injection of 0.1 mL SPAN's tuberculin (purified protein derivative/5 tuberculin units/0.1 mL) (Span Diagnostic Ltd., Murat, India) was negative after 72 h. Investigations, including total and differential leukocyte count, erythrocyte sedimentation rate, serum biochemistry, and renal and liver function tests, were within the normal range, as was a chest X-ray. Figure 1. Tuberculosis verrucosa cutis before (a) and after (b) antitubercular therapy (ATT) Hematoxylin and eosin-stained sections prepared from the biopsy taken from the lesion revealed noteworthy changes in the epidermis and the dermis. The former was marked by the presence of hyperkeratosis, acanthosis, and papillomatosis, whilst the latter contained tubercle granulomas. Each of the granulomas was well formed and consisted of large numbers of lymphocytes, histiocytes, and foreign body (Langerhans') giant cells (Fig. 2). Caseation necrosis and acid-fast bacilli could not be demonstrated. The preceding revelations were fairly conducive to the diagnosis. Accordingly, antitubercular therapy (ATT), comprising 450 mg of rifampicin, 300 mg of isonicotinic acid hydrazide, and 800 mg of ethambutol, was recommended for oral administration each day for 60 days. The outcome of the treatment was satisfactory, resulting in perceptible regression of the skin lesion (Fig. 1b). The patient was advised to continue the treatment for another 30 days, after which 450 mg of rifampicin and 300 mg of isonicotinic acid hydrazide were to be continued for another 6 months. Figure 2. Tuberculosis verrucosa cutis depicting well-formed tubercle(s) comprising lymphocytes, histiocytes, neutrophils, and a few giant cells (hematoxylin and eosin, × 100) [source] Erythema induratum with pulmonary tuberculosis: histopathologic features resembling true vasculitisINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 3 2001Yong Suk Lee MD A 22-year-old South Korean woman presented with a 4-month history of several nodules on both legs. She looked healthy, but suffered from tenderness and swelling of the legs. Physical examination showed multiple, nonulcerating, erythematous nodules occurring on the calves, knee joints, and thighs (Fig. 1). A biopsy specimen of the skin revealed necrotizing vasculitis of medium-sized arteries with fibrinoid necrosis at the border between the dermis and the subcutis. Dense cellular infiltrates, including numerous neutrophils and lymphocytes, presented within and around the vessel walls as in polyarteritis nodosa, with some eosinophils (Fig. 2A,B). There were no other generalized symptoms. She was diagnosed with cutaneous polyarteritis nodosa and was initially treated with systemic steroids. She was given an intravenous injection of Solu-Cortef, 60 mg/6 h for 7 days. This was replaced with oral prednisolone for 2 weeks. The skin lesions and symptoms improved. Figure 1. Small, nut-sized, erythematous, brown-colored nodules and patches on the lower extremities, even above the knee joints Figure 2. (A) Dense infiltration within and around artery (× 40). (B) Slightly expanded lobular panniculitis with vasculitis (× 100) Six months later, she complained of general weakness and recurrent skin lesions. Purified protein derivative (PPD) test gave a moderate positive reaction and chest X-ray examination showed the features of pulmonary tuberculosis: radio-opaque infiltrations in the right lower lung field. A repeated biopsy revealed mild vasculitis with more diffuse lobular infiltrations of the subcutaneous tissue compared with the former specimen. Polymerase chain reaction (PCR) and tissue culture for Mycobacterium tuberculosis were performed from a biopsy specimen. DNA was extracted from skin tissue with an AplisystemTM DNA/RNA detection kit using the resin-mediated boiling method (Stargene, Seoul, South Korea). The primers were designed on the basis of the M. tuberculosis gene IS6110 target (sense primer, 5,-CCA GAT GCA CCG TCG AAC GGC TGA T-3, antisense primer, 5,-CGC TCG CTG AAC CGG ATC GAT GTG T-3,). The amplification was performed with uracil- N -glycosylase (UNG), to prevent carry-over contamination, and internal control primers, to correct for false-negative reaction (Kox LF, Rhienthong D, Miranda AM et al. A more reliable PCR for detection of Mycobacterium tuberculosis in clinical samples. J Clin Microbiol 1994; 32: 672,678; Longo MC, Berninger MS, Hartley JL. Use of uracil DNA glycosylase to control carry-over contamination in polymerase chain reactions. Gene 1990; 93: 125,128). According to the manufacturer's instructions, amplification was carried out for 40 cycles with denaturation at 94 °C for 40 s, annealing at 70 °C for 1 min, and extension at 72 °C for 1 min in a thermal cycler (Perkin,Elmer Cetus, Norwalk, CT, USA). The results of PCR and tissue culture for M. tuberculosis using the biopsy specimen were all negative (Fig. 3). Figure 3. Negative result in PCR for M. tuberculosis (negative control is not shown; M, marker; P, positive control; I, internal control; S, specimen) The patient was finally diagnosed with erythema induratum with pulmonary tuberculosis and was started on antituberculosis medication (isoniazid 400 mg, rifampicin 600 mg, ethambutol 800 mg, and pyrazinamide 1500 mg daily). She showed prompt improvement after 2 weeks of medication. After 9 months of antituberculosis therapy, her skin lesions and chest X-ray had cleared. She was followed up for 4 months with no recurrence of skin and pulmonary lesions. [source] A novel genotypic test for rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates by a multiplex probe arrayJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2007S.-L. Zhang Abstract Aims:, To develop and evaluate a novel genotypic test for rapid detection of rifampicin and isoniazid resistance of multidrug-resistant (MDR) Mycobacterium tuberculosis isolates by a multiplex probe array. Methods and Results:, A multiplex probe array was designed for genotypic test to simultaneously screen the mutations of rpoB, katG, inhA and ahpC genes, associated with rifampin and isoniazid resistance in M. tuberculosis, with a probe detecting one of the recently confirmed genetic markers of isoniazid resistance ahpC -6 and -9 locus added. By using the genotypic test developed, 52 MDR isolates were identified, among which 46 isolates had mutations in rpoB (88·5%) and 45 at codon 315 of katG, regulatory region of inhA and oxyR - ahpC intergenic region (86·5%), whereas all 35 susceptible isolates identified showed a wild-type hybridization pattern. The sensitivity and specificity were 88·5% and 100% for rifampicin resistance, and 86·5% and 100% for isoniazid resistance, respectively. Conclusion:, A rapid and simultaneous detection of rifampicin and isoniazid resistance caused by the mutations of rpoB, katG, inhA and ahpC genes in M. tuberculosis isolates could be achieved by a multiplex probe array developed. Significance and Impact of the Study:, This genotypic test protocol has the potential to be developed on clinical application for the rapid detection of drug resistant M. tuberculosis isolates before an efficient chemotherapy is initiated. [source] Transmission of cotton seed and boll rotting bacteria by the southern green stink bug (Nezara viridula L.)JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007E.G. Medrano Abstract Aims:, To determine the ability of the southern green stink bug (SGSB) (Nezara viridula L.) to transmit Pantoea agglomerans into cotton (Gossypium hirsutum) bolls. Methods and Results:, An SGSB laboratory colony was kept on fresh green beans. A P. agglomerans variant resistant to rifampicin (Rif) (strain Sc 1-R) was used as the opportunistic cotton pathogen. Adult insects were individually provided green beans that were sterilized and then soaked in either sterile water or in a suspension of strain Sc 1-R. Insects were individually caged with an unopened greenhouse-grown cotton boll. After 2 days, live SGSB were collected, surfaced sterilized, ground, serially diluted, and then plated on nonselective media and media amended with Rif. Exterior and interior evidence of feeding on bolls was recorded 2 weeks after exposure to insects. Seed and lint tissue were harvested, ground, serially diluted, and then plated on media with and without Rif. Bacteria were recovered on nonselective media from all insects, and from seed and lint with signs of insect feeding at concentrations ranging from 102 to 109 CFU g,1 tissue. The Sc 1-R strain was isolated only from insects exposed to the marked strain and from seed and lint of respective bolls showing signs of insect feeding. Evidence of insect feeding on the exterior wall of the carpel was not always apparent (47%), whereas feeding was always observed (100%) on the interior wall in association with bacterial infections of seed and lint. Conclusions:,Nezara viridula readily ingested the opportunistic P. agglomerans strain Sc 1-R and transmitted it into unopened cotton bolls. Infections by the transmitted Sc 1-R strain caused rotting of the entire locule that masked internal carpel wounds incurred by insect feeding. Bacteria were recovered from penetration points by insects not exposed to the pathogen, but locule damage was limited to the area surrounding the feeding site (c. 3 mm). Significance and Impact of the Study:, This is the first study that demonstrates the ability of SGSB to acquire and transmit plant pathogenic bacteria into cotton bolls. [source] Diversity of soil mycobacterium isolates from three sites that degrade polycyclic aromatic hydrocarbonsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007C.D. Miller Abstract Aims:, This paper investigates the diversity of polycyclic aromatic hydrocarbon (PAH)-degrading mycobacterium isolates from three different sites within United States: Montana, Texas and Indiana. Methods and Results:, All five mycobacterium isolates differed in chromosomal restriction enzyme-fragmentation patterns; three isolates possessed linear plasmids. The DNA sequence between the murA and rRNA genes were divergent but the sequence upstream of nidBA genes, encoding a dioxygenase involved in pyrene oxidation, was more highly conserved. Long-chain fatty acid analysis showed most similarity between three isolates from the same Montana site. All isolates were sensitive to rifampicin and isoniazid, used in tuberculosis treatment, and to syringopeptins, produced by plant-associated pseudomonads. Biofilm growth was least for isolate MCS that grew on plate medium as rough-edged colonies. The patterns of substrate utilization in Biolog plates showed clustering of the Montana isolates compared with Mycobacterium vanbaalenii and Mycobacterium gilvum. Conclusion:, The five PAH-degrading mycobacterium isolates studied differ in genetic and biochemical properties. Significance and Impact of the Study:, Different properties with respect to antibiotic susceptibility, substrate utilization and biofilm formation could influence the survival in soil of the microbe and their suitability for use in bioaugmentation. [source] CYP3A4 and pregnane X receptor humanized miceJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 4 2007Frank J. Gonzalez Abstract Marked species differences exist in P450 expression and activities. In order to produce mouse models that can be used to more accurately predict human drug and carcinogen metabolism, P450- and xenobiotic receptor humanized mice are being prepared using bacterial artificial chromosomes (BAC) and P1 phage artificial chromosomes (PAC) genomic clones. In some cases, transgenic mice carrying the human genes are bred with null-mice to produce fully humanized mice. Mice expressing human CYP1A1, CYP1A2, CYP2E1, CYP2D6, CYP3A4, and CYP3A7 were generated and characterized. Studies with the CYP3A4-humanized (hCYP3A4) mouse line revealed new information on the physiological function of this P450 and its role in drug metabolism in vivo. With this mouse line, CYP3A4, under certain circumstances, was found to alter the serum levels of estrogen resulting in deficient lactation and low pup survival as a result of underdeveloped mammary glands. This hCYP3A4 mouse established the importance of intestinal CYP3A4 in the pharmacokinetics of orally administered drugs. The hCYP3A4 mice were also used to establish the mechanisms of potential gender differences in CYP3A4 expression (adult female > adult male) that could account for human gender differences in drug metabolism and response. The pregnane X receptor (PXR) is also involved in induction of drug metabolism through its target genes including CYP3A4. Since species differences exist in ligand specificity between human and mice, a PXR -humanized mouse (hPXR) was produced that responds to human PXR activators such as rifampicin but does not respond to the rodent activator pregnenalone 16,-carbonitrile. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:158,162, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20173 [source] Effect of silybin and its glycosides on the expression of cytochromes P450 1A2 and 3A4 in primary cultures of human hepatocytesJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 3 2005Pavel Kosina Abstract Four ,-glycosides of flavonoligan silybin, i.e. silybin ,-galactoside, silybin ,-glucoside, silybin ,-maltoside, silybin ,-lactoside were synthesized in order to improve silybin water solubility and bioavailability (K,en et al., J Chem Soc, Perkin Trans 1, 2467,2474, 1997). The presented paper deals with the effect of silybin and its synthetic ,-glycosides on the expression of two major cytochrome P450 isoforms, CYP1A2 and CYP3A4. Primary cultures of human hepatocytes were the model of choice. mRNAs were analyzed using Northern blot and P-radiolabelled probes. CYP protein content was determined by immunoblotting using specific antibodies. Silybin and its ,-glycosides do not induce expression of CYP1A2 and CYP3A4. Tested compounds did not affect inducible expression of CYP1A2 and CYP3A4 by dioxin and rifampicin, respectively, as evaluated at the level of mRNAs and proteins. Silybin and its ,-glycosides do not interfere with the expression of CYP1A2 and CYP3A4, are not likely to produce drug,drug interactions in terms of the inducibility of two important cytochromes P450. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:149,153, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20066 [source] Modulation of UDP-glucuronosyltransferase 1A1 in primary human hepatocytes by prototypical inducers,JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2005Cornelia M. Smith Abstract The primary objective of this study was to evaluate the modulation of UGT1A1 expression in human hepatocytes using prototypical CYP450 inducers. A bank of 16 human livers was utilized to obtain an estimate of the range of UGT1A1 protein expression and catalytic activity. Concentration-dependent changes in UGT1A1 response were evaluated in hepatocyte cultures after treatment with 3-methylchloranthrene, ,-napthoflavone, rifampicin, or phenobarbital. Pharmacodynamic analyses of UGT1A1 expression were conducted and compared to those of CYP450 after treatment with inducers in 2,3 different hepatocyte preparations. Additionally, expression of UGT1A1 mRNA and protein was evaluated in human hepatocytes treated with 14 different compounds known to activate differentially the human pregnane-X-receptor or constitutive androstane receptor. Pharmacodynamic modeling revealed EC50 values statistically significant between UGT1A1 and CYP2B6 after treatment with PB, but not statistically distinguishable between UGT1A1 and CYP's 1A2 or 3A4 after treatment with 3-methylchloranthrene or rifampicin, respectively. UGT1A1 was most responsive to the pregnane-X-receptor-agonists rifampicin, ritonavir, and clotrimazole at the mRNA level and, to a lesser extent, the constitutive androstane receptor-activators, phenobarbital and phenytoin. Pharmacodynamic analyses support a mechanism of coordinate regulation between UGT1A1 and a number of CYP450 enzymes by multiple nuclear receptors. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:96,108, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20058 [source] Synergism of microwave irradiation and enzyme catalysis in synthesis of isoniazidJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2007Ganapati D Yadav Abstract Isoniazid is a useful antitubercular drug widely employed in combination therapy with rifampicin. The synthesis of isoniazid from ethyl isonicotinate and hydrazine hydrate was studied in non-aqueous media via lipase-catalyzed hydrazinolysis under both conventional heating and microwave irradiation by using different supported lipases. Among three different commercial lipases used, namely Novozym 435 (Candida antarctica lipase), Lipozyme RM IM (Rhizomucor miehei lipase) and Lipozyme TL IM (Thermomyces lanuginosus lipase), Novozym 435 was found to be the most effective, with conversion of 54% for equimolar concentrations at 50 °C in 4 h. The rate of reaction as well as final conversion increased synergistically under microwave irradiation in comparison with conventional heating, which showed 36.4% conversion, even after 24 h, for the control experiment. Effects of various process parameters such as speed of agitation, catalyst loading, substrate concentration, product concentration and temperature were studied. A kinetic model is also described. Copyright © 2007 Society of Chemical Industry [source] GSTT1 and GSTM1 gene deletions are not associated with hepatotoxicity caused by antitubercular drugsJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 4 2010S. Chatterjee MD Summary Background and objective:, Susceptibility to antitubercular drug (ATD)-induced hepatotoxicity may be genetically mediated, with variant alleles of genes such as N -acetyltransferase (NAT2) and CYP2E1 reported as risk factors. Two studies of Asian populations have reported that GSTM1*0/*0 (null) genotype was a likely predictor of hepatotoxicity, whereas another of a Caucasian population implicated GSTT1*0/*0. We undertook a prospective case,control study to investigate whether GSTM*0/*0 and GSTT1*0/*0 were risk factors for ATD-induced hepatotoxicity. Methods:, Pulmonary tuberculosis patients on isoniazid, rifampicin and pyrazinamide who developed hepatotoxicity using defined criteria were prospectively identified. These cases were then matched with at least one control subject on the same drugs but without hepatotoxicity. Genotyping for GSTM1 and GSTT1 was performed by multiplex PCR on genomic DNA. The odds ratios for the frequency of specific GSTM1 and GSTT1 homozygotes in the case and control subjects were calculated to test for association between the genotypes and hepatotoxicity. Results and discussion:, Hundred and fifty-one subjects (51 cases, 100 controls) were enrolled. Odds ratio for GSTM1 null genotype was 1·00 (95% CI 0·51,1·97) and GSTT1 null was 2·02 (95% CI 0·39,10·39), respectively, showing that these genotypes are not associated with hepatotoxicity. Conclusion:,GSTM1 *0/*0 or GSTT1 *0/*0 or both null genotypes, do not appear to be associated with ATD-induced hepatotoxicity in our Indian population. [source] PREVALENCE AND ANTIMICROBIAL RESISTANCE OF LISTERIA SPECIES IN FOOD PRODUCTS IN BANGKOK, THAILANDJOURNAL OF FOOD SAFETY, Issue 1 2010SIRIPORN STONSAOVAPAK ABSTRACT A total of 380 meat and meat products, dairy and dairy products, fresh vegetables, fresh seafood, and ready-to-eat food samples from supermarkets in Bangkok, Thailand were collected and analyzed for the occurrence of Listeria spp. and of Listeria monocytogenes. The overall incidence of Listeria spp. was 16.8%, most of them were isolated from raw meat and vegetables. L. monocytogenes was isolated from 18 (4.7%) out of 380 studied samples. Other species isolated were L. innocua (6.6%), L. ivanovii (0.8%), L. seeligeri (0.5%), L. grayi (1.6%) and L. welshimeri (2.6%). The antimicrobial susceptibilities of the 64 isolate of Listeria spp. were also examined by the standard disk diffusion method. Listeria spp. were resistant to penicillin (6.3%), chloramphenicol (3.1%) and tetracycline (1.6%), but sensitive to amoxicillin, vancomycin, ampicillin, rifampicin and sulfamethoxazole. PRACTICAL APPLICATIONS Listeria monocytogenes prevalence in food products in Bangkok has been documented. More studies on the occurrence of L. monocytogenes are needed to establish microbiological criteria of foods in the country. The findings of our study, increases in antibiotic resistance among Listeria spp. will provide useful information for the development of public health policy in the use of antimicrobials in food animal production. [source] Interaction between rifampicin and methadoneACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2009B. le Polain de W No abstract is available for this article. [source] Changes in HIV RNA viral load, CD4+ T-cell counts, and levels of immune activation markers associated with anti-tuberculosis therapy and cotrimoxazole prophylaxis among HIV-infected tuberculosis patients in Abidjan, Côte d'IvoireJOURNAL OF MEDICAL VIROLOGY, Issue 2 2005Mireille Kalou We analyzed changes in plasma human immunodeficiency virus (HIV)-1 viral load, CD4+ T-cell count, and markers of immune activation markers at start of treatment of tuberculosis and 12 months after among 44 HIV-1-infected patients with newly diagnosed, sputum-smear positive for Mycobacterium tuberculosis pulmonary in fection. All patients received a standard regimen of 6 months of rifampicin and isoniazid with first 2 months of pyrazinamid with or without cotrimoxazole. Compared with values at start of treatment, median viral load increased by a median of 0.64 log10 copies/ml after 12 months of follow-up (P,=,0.0002). Median CD4+ T-cell counts were 393 cells/L at start of treatment and 370 cells/L after 12 months of follow-up (P,=,0.61). Levels of serum activation markers decreased significantly at 12 months of follow-up of the patients for both patients on standard and cotrimoxazole treatment. Levels of viral load, CD4+ T-cell counts, and markers of immune activation were not different for patients on standard treatment of tuberculosis compared with those on standard and cotrimoxazole treatment. Levels of serum activation markers decreased significantly at 12 months of follow-up of the patients for both patients on standard and cotrimoxazole treatment. Because viral load is a predictor of disease progression, its persistent elevated levels in blood of HIV-infected patients co-infected with tuberculosis, who successfully complete TB treatment, may account for the high mortality observed in this population. J. Med. Virol. 75:202,208, 2005. © 2004 Wiley-Liss, Inc. [source] Species-specific interaction of HIV protease inhibitors with accumulation of cholyl-glycylamido-fluorescein (CGamF) in sandwich-cultured hepatocytesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2010Zhi-wei Ye Abstract Using sandwich-cultured hepatocytes from rat, dog, pig, and human, we investigated the species-specificity of interaction of HIV protease inhibitors (PI) with in vitro hepatic accumulation of the bile salt analogue cholyl-glycylamido-fluorescein (CGamF). Extracellular sodium depletion or coincubation with the OATP/Oatp inhibitors rifampicin and digoxin revealed that about 35% of active CGamF accumulation was mediated by Ntcp/NTCP in rat and human hepatocytes, while the contribution of this sodium-dependent transporter reached 50,60% in dog and pig hepatocytes. One or more sodium-independent transporters, likely belonging to the Oatp/OATP family, constitute a major transport mechanism for CGamF accumulation. Various HIV PI (0.5, 5, 25,µM) exhibited pronounced species differences in their interaction with active CGamF accumulation (1,µM), although some similarity was observed between the dog and human interaction profiles when HIV PI were tested at 0.5,µM. Atazanavir, indinavir, and darunavir were the most potent inhibitors of CGamF accumulation in human hepatocytes. Potent inhibition of CGamF accumulation by ritonavir in rat hepatocytes contrasted with a weak effect in human hepatocytes. Thorough characterization of in vitro disposition of probe substrates in preclinical species compared to human hepatocytes will ultimately support a better insight in species-specific mechanisms underlying drug interactions and drug-mediated toxicity. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2886,2898, 2010 [source] | |||||||||||||||||||||||||||||||