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Luminal pH (luminal + ph)
Selected AbstractsElectrophysiological characterization of electrolyte and nutrient transport across the small intestine in horsesJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3 2009A. Cehak Summary The aim of this study was to characterize the transport mechanisms of electrolytes and nutrients across the jejunum of nine healthy horses electrophysiologically. The stripped mucosa was mounted in Ussing chambers and tissue conductances (Gt) and short circuit currents (Isc) were continuously monitored. After blocking the sodium and potassium channels with amiloride, tetraethylammonium chloride (TEA) and barium, chloride secretion was stimulated by carbachol and forskolin. Subsequently, chloride channels were inhibited by 4,4,-diisothiocyanato-stilbene-2,2,-disulfonic acid, 5-nitro-2-(3-phenylpropylamino)benzoic acid, CFTRinh -172, N -(2-naphtalenyl)-(3.5-dibromo-2.4-dihydroxyphenyl)methylene glycine hydrazide (GlyH-101) and glibenclamide and their dose,response effect was investigated. The response to glucose, l -alanine and glycyl- l -glutamine was determined at two different mucosal pH values (pH 7.4 and 5.4 respectively). Mean basal Isc was ,0.47 ± 0.31 ,Eq/cm2h and mean Gt was 22.17 ± 1.78 mS/cm2. Amiloride and TEA did not alter the baseline Isc. Barium, carbachol and forskolin significantly increased Isc. Irrespective of the dose, none of the chloride inhibitors changed Isc. All nutrients induced a significant increase in Isc with the increase being significantly higher at pH 7.4 than at pH 5.4. In conclusion, there is evidence that chloride secretion in horses may be different from respective transport mechanisms in other species. The glucose absorption is suggestive of a sodium-dependent glucose cotransporter 1. However, a decrease in luminal pH did not stimulate current response to peptides as shown for other mammals. [source] Site-specific contribution of proton-coupled folate transporter/haem carrier protein 1 in the intestinal absorption of methotrexate in ratsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2009Tomoharu Yokooji Abstract Objectives Methotrexate is reportedly a substrate for proton-coupled folate transporter/haem carrier protein 1 (PCFT/HCP1) and reduced folate carrier 1 (RFC1). In this study, we examined the contribution of PCFT/HCP1 and RFC1 in the intestinal absorption of methotrexate in rats. Methods Western blot analysis was carried out to evaluate the protein levels of PCFT/HCP1 and multidrug resistance-associated protein 2 in brush-border membrane of rat small intestine. Mucosal uptake of methotrexate was studied in the rat everted small intestine and an in-situ intestinal perfusion study of methotrexate was also carried out in rats. Key findings In transport studies using everted intestine, the mucosal methotrexate influx rate in proximal intestine at pH 5.5 was significantly greater than that at pH 7.4. Coadministration of folate or its analogues, such as folinate and 5-methyltetrahydrofolate, substrates for both PCFT/HCP1 and RFC1, significantly suppressed the methotrexate influx at pH 5.5, whereas thiamine pyrophosphate, an inhibitor for RFC1 alone, exerted no significant effect. Western blot analysis showed higher PCFT/HCP1 expression in proximal than distal small intestine. In distal small intestine, methotrexate influx rate was low and was not pH dependent. Also, folate and its analogues exerted no significant effect on methotrexate absorption. Conclusions Based on the present and our previous results, the site-specific contributions of various transporters including PCFT/HCP1 in methotrexate intestinal absorption were discussed. The variation in luminal pH and the involvement of multiple transporters in methotrexate absorption may cause variation in oral bioavailability among patients. [source] Comparison of gastric emptying of a nondigestible capsule to a radio-labelled meal in healthy and gastroparetic subjectsALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2008B. KUO Summary Background, Gastric emptying scintigraphy (GES) using a radio-labelled meal is used to measure gastric emptying. A nondigestible capsule, SmartPill, records luminal pH, temperature, and pressure during gastrointestinal transit providing a measure of gastric emptying time (GET). Aims, To compare gastric emptying time and GES by assessing their correlation, and to compare GET and GES for discriminating healthy subjects from gastroparetics. Methods, Eighty-seven healthy subjects and 61 gastroparetics enrolled with simultaneous SmartPill and GES. Fasted subjects were ingested capsule and [99mTc]-SC radio-labelled meal. Images were obtained every 30 min for 6 h. Gastric emptying time and percentage of meal remaining at 2/4 h were determined for each subject. The sensitivity/specificity and receiver operating characteristic analysis of each measure were determined for each subject. Results, Correlation between GET and GES-4 h was 0.73 and GES-2 h was 0.63. The diagnostic accuracy from the receiver operating characteristic curve between gastroparetics and healthy subjects was GET = 0.83, GES-4 h = 0.82 and GES-2 h = 0.79. The 300-min cut-off time for GET gives sensitivity of 0.65 and specificity of 0.87 for diagnosis of gastroparesis. The corresponding sensitivity/specificity for 2 and 4 h standard GES measures were 0.34/0.93 and 0.44/0.93, respectively. Conclusion, SmartPill GET correlates with GES and discriminates between healthy and gastroparetic subjects offering a nonradioactive, standardized, ambulatory alternative to scintigraphy. [source] Lack of effect of ranitidine on gastric luminal pH and mucosal PCO2 during the first day in the ICUACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2005S. M. Jakob Background:, Histamine2 (H2)-blocking agents can attenuate intragastric CO2 -production by reducing gastric acid secretion and preventing the interaction between H+ and bicarbonate. However, gastric acid production may be impaired in acute circulatory failure due to poor mucosal perfusion, and H2 -blockade could further impair mucosal perfusion. Methods:, Forty patients with acute circulatory and/or respiratory failure, age 61 ± 16 years (mean ± SD), APACHE II score 21 ± 7, and SOFA score 8 ± 3, received randomly either ranitidine, 50 mg (R) or placebo (P) every 8 h. Gastric intraluminal pH (gpH; antimony probe with external reference electrode) and mucosal pCO2 (prCO2, semicontinuous air-tonometry) were measured during 24 h, and blood gases were taken at 6-h intervals. Results:, Gastric intraluminal pH was 4.3 ± 2.4 in P and 5.1 ± 1.6 in R (NS). Mean prCO2 was 6.8 ± 2.7 kPa in P and 7.4 ± 2.1 kPa in R, and mucosal-arterial pCO2 gradient (,pCO2) was 2.2 ± 2.9 kPa and 2.4 ± 2.4 kPa, respectively (NS). Within-patient variabilities of gpH and prCO2 were not influenced by ranitidine. A posthoc analysis revealed that non-survival in R was associated with a low mucosal pHi after 24 h (P = 0.002). This was explained by a low arterial pH but not by differences in gpH or prCO2. Conclusion:, In acute respiratory and circulatory failure, H2 blockade has an inconsistent impact on gpH and does not reduce variabilities of gpH or prCO2. [source] | ||||||||||