Home About us Contact
|
Home About us Contact | ||
|
|
||
Adenosine Monophosphate (adenosine + monophosphate)
Kinds of Adenosine Monophosphate Selected AbstractsSynergistic Effect of Porcine Follicular Fluid and Dibutyryl Cyclic Adenosine Monophosphate on Development of Parthenogenetically Activated Oocytes from Pre-Pubertal GiltsREPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2010AB Nascimento Contents This study investigated the effect of porcine follicular fluid (PFF) and dibutyryl cyclic adenosine monophosphate (dbcAMP) during in vitro maturation (IVM) of porcine oocytes on meiotic maturation, fertilization and embryo development, and compared the effect of supplementing the embryo culture media with PFF or foetal bovine serum (FBS) on embryo development. Oocytes from pre-pubertal gilts were IVM for 44 h, and parthenogenetically activated or in vitro -fertilized. Embryos were cultured in porcine zygote medium (PZM3) for 7 days. Cleavage and blastocyst rates were evaluated at 48 h and 7 days of culture. The supplementation of the IVM medium with 25% PFF and 1 mm dbcAMP for the first 22 h resulted in more (p < 0.05) embryos developing to the blastocyst stage as compared with the inclusion of dbcAMP alone. The dbcAMP + PFF combination increased (p < 0.05) the average number of nuclei per blastocyst as compared with either of these components alone or in its absence. A synergistic effect of dbcAMP + PFF during IVM was also reflected in the capacity of oocytes to regulate sperm penetration and prevent polyspermy, as twice as many oocytes from the control group were penetrated by more than one sperm as compared with those matured in the presence of both dbcAMP and PFF. The supplementation of PZM3 with 10% FBS from days 5 to 7 of culture significantly improved the total cell quantity in embryos derived either from control or dbcAMP + PFF matured oocytes. There was no effect on the total cell quantity when FBS was replaced by the same concentration of PFF. These studies showed that dbcAMP, PFF and FBS can improve both the quantity (57.3% vs 41.5%) and quality (74.8 vs 33.3 nuclei) of porcine blastocysts derived from oocytes recovered of pre-pubertal gilts. [source] Extracellular cAMP inhibits P2X3 receptors in rat sensory neurones through G protein-mediated mechanismACTA PHYSIOLOGICA, Issue 2 2010M. V. Mamenko Abstract Aim:, To identify the mechanisms of P2X3 receptor inhibition by extracellular cyclic adenosine monophosphate (cAMP) in rat dorsal root ganglion (DRG) neurones. Methods:, Whole-cell currents were measured in cultured DRG neurones using the combination of voltage and concentration clamp. Results:, We have found that extracellular cAMP inhibits P2X3 -mediated currents in a concentration- and use-dependent manner. The P2X3 currents, activated by ATP applied every 4 min, were inhibited by 55% in the presence of 10 ,m cAMP and by 81% in the presence of 30 ,m cAMP. At 8 min interval between ATP applications the same concentration of cAMP did not alter the currents. Addition of 0.5 mm of guanosine 5,- O -(2-thiodiphosphate) to intracellular solution blocked the inhibitory action of cAMP. The inhibitory effects of cAMP were not mimicked by extracellular application of 30 ,m adenosine. Conclusions:, In this paper, we demonstrate, for the first time, that extracellular application of cAMP to rat sensory neurones inhibits P2X3 receptors via a G protein-coupled mechanism in a use-dependent manner, thus indicating the neuronal expression of specific plasmalemmal cAMP receptor. [source] A novel role of differentiation-inducing factor-1 in Dictyostelium development, assessed by the restoration of a developmental defect in a mutant lacking mitogen-activated protein kinase ERK2DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2000Hidekazu Kuwayama It has been previously reported that the differentiating wild-type cells of Dictyostelium discoideum secrete a diffusible factor or factors that are able to rescue the developmental defect in the mutant lacking extracellular signal-regulated kinase 2 (ERK2), encoded by the gene erkB. In the present study, it is demonstrated that differentiation-inducing factor-1 (DIF-1) for stalk cells can mimic the role of the factor(s) and the mechanism of the action of DIF-1 in the erkB null mutant is also discussed. The mutant usually never forms multicellular aggregates, because of its defect in cyclic adenosine monophosphate (cAMP) signaling. In the presence of 100 n M DIF-1, however, the mutant cells formed tiny slugs, which eventually developed into small fruiting bodies. In contrast, DIF-1 never rescued the developmental arrest of other Dictyostelium mutants lacking adenylyl cyclase A (ACA), cAMP receptors cAR1 and cAR3, heterotrimeric G-protein, the cytosolic regulator of ACA, or the catalytic subunit of cAMP-dependent protein kinase (PKA-C). Most importantly, it was found that DIF-1 did not affect the cellular cAMP level, but rather elevated the transcriptional level of pka during the development of erkB null cells. These results suggest that DIF-1 may rescue the developmental defect in erkB null cells via the increase in PKA activity, thus giving the first conclusive evidence that DIF-1 plays a crucial role in the early events of Dictyostelium development as well as in prestalk and stalk cell induction. [source] Dopamine modulation of the In vivo acetylcholine response in the Drosophila mushroom bodyDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2009Vitold Tsydzik Abstract Olfactory sensory information in Drosophila is transmitted through antennal lobe projections to Mushroom Body neurons (Kenyon cells) by means of cholinergic synapses. Application of acetylcholine (ACh) and odors produce significant increases in intracellular calcium ([Ca2+]i) in these neurons. Behavioral studies show that Kenyon cell activity is modulated by dopaminergic inputs and this modulation is thought to be the basis for an olfactory conditioned response. However, quantitative assessment of the synaptic inputs to Kenyon cells is currently lacking. To assess neuronal activity under in vivo conditions, we have used the endogenously-expressed camgaroo reporter to measure [Ca2+]i in these neurons. We report here the dose-response relationship of Kenyon cells for ACh and dopamine (DA). Importantly, we also show that simultaneous application of ACh and DA results in a significant decrease in the response to ACh alone. In addition, we show inhibition of the ACh response by cyclic adenosine monophosphate. This is the first quantitative assessment of the effects of these two important transmitters in this system, and it provides an important basis for future analysis of the cellular mechanisms of this well established model for associative olfactory learning. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] PACAP inhibits delayed rectifier potassium current via a cAMP/PKA transduction pathway: evidence for the involvement of IK in the anti-apoptotic action of PACAPEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004Y. A. Mei Abstract Activation of potassium (K+) currents plays a critical role in the control of programmed cell death. Because pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to inhibit the apoptotic cascade in the cerebellar cortex during development, we have investigated the effect of PACAP on K+ currents in cultured cerebellar granule cells using the patch-clamp technique in the whole-cell configuration. Two types of outward K+ currents, a transient K+ current (IA) and a delayed rectifier K+ current (IK) were characterized using two different voltage protocols and specific inhibitors of K+ channels. Application of PACAP induced a reversible reduction of the IK amplitude, but did not affect IA, while the PACAP-related peptide vasoactive intestinal polypeptide had no effect on either types of K+ currents. Repeated applications of PACAP induced gradual attenuation of the electrophysiological response. In the presence of guanosine 5,-[,thio]triphosphate (GTP,S), PACAP provoked a marked and irreversible IK depression, whereas cell dialysis with guanosine 5,-[,thio]diphosphate GDP,S totally abolished the effect of PACAP. Pre-treatment of the cells with pertussis toxin did not modify the effect of PACAP on IK. In contrast, cholera toxin suppressed the PACAP-induced inhibition of IK. Exposure of granule cells to dibutyryl cyclic adenosine monophosphate (dbcAMP) mimicked the inhibitory effect of PACAP on IK. Addition of the specific protein kinase A inhibitor H89 in the patch pipette solution prevented the reduction of IK induced by both PACAP and dbcAMP. PACAP provoked a sustained increase of the resting membrane potential in cerebellar granule cells cultured either in high or low KCl-containing medium, and this long-term depolarizing effect of PACAP was mimicked by the IK specific blocker tetraethylammonium chloride (TEA). In addition, pre-incubation of granule cells with TEA suppressed the effect of PACAP on resting membrane potential. TEA mimicked the neuroprotective effect of PACAP against ethanol-induced apoptotic cell death, and the increase of caspase-3 activity observed after exposure of granule cells to ethanol was also significantly inhibited by TEA. Taken together, the present results demonstrate that, in rat cerebellar granule cells, PACAP reduces the delayed outward rectifier K+ current by activating a type 1 PACAP (PAC1) receptor coupled to the adenylyl cyclase/protein kinase A pathway through a cholera toxin-sensitive Gs protein. Our data also show that PACAP and TEA induce long-term depolarization of the resting membrane potential, promote cell survival and inhibit caspase-3 activity, suggesting that PACAP-evoked inhibition of IK contributes to the anti-apoptotic effect of the peptide on cerebellar granule cells. [source] Nanofibrous Patches for Spinal Cord RegenerationADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Yiqian Zhu Abstract The difficulty in spinal cord regeneration is related to the inhibitory factors for axon growth and the lack of appropriate axon guidance in the lesion region. Here scaffolds are developed with aligned nanofibers for nerve guidance and drug delivery in the spinal cord. Blended polymers including poly(L -lactic acid) (PLLA) and poly(lactide- co -glycolide) (PLGA) are used to electrospin nanofibrous scaffolds with a two-layer structure: aligned nanofibers in the inner layer and random nanofibers in the outer layer. Rolipram, a small molecule that can enhance cAMP (cyclic adenosine monophosphate) activity in neurons and suppress inflammatory responses, is immobilized onto nanofibers. To test the therapeutic effects of nanofibrous scaffolds, the nanofibrous scaffolds loaded with rolipram are used to bridge the hemisection lesion in 8-week old athymic rats. The scaffolds with rolipram increase axon growth through the scaffolds and in the lesion, promote angiogenesis through the scaffold, and decrease the population of astrocytes and chondroitin sulfate proteoglycans in the lesion. Locomotor scale rating analysis shows that the scaffolds with rolipram significantly improved hindlimb function after 3 weeks. This study demonstrates that nanofibrous scaffolds offer a valuable platform for drug delivery for spinal cord regeneration. [source] Non-antagonistic relationship between mitogenic factors and cAMP in adult Schwann cell re-differentiationGLIA, Issue 9 2009Paula V. Monje Abstract The expression of myelination-associated genes (MGs) can be induced by cyclic adenosine monophosphate (cAMP) elevation in isolated Schwann cells (SCs). To further understand the effect of known SC mitogens in the regulation of SC differentiation, we studied the response of SCs isolated from adult nerves to combined cAMP, growth factors, including neuregulin, and serum. In adult SCs, the induction of MGs by cAMP coincided with the loss of genes expressed in non-myelin-forming SCs and with a change in cell morphology from a bipolar to an expanded epithelial-like shape. Prolonged treatment with high doses of cAMP-stimulating agents, as well as low cell density, was required for the induction of SC differentiation. Stimulation with serum, neuregulin alone, or other growth factors including PDGF, IGF and FGF, increased SC proliferation but did not induce the expression of MGs or the associated morphological change. Most importantly, when these factors were administered in combination with cAMP-stimulating agents, SC proliferation was synergistically increased without reducing the differentiating activity of cAMP. Even though the initiation of DNA synthesis and the induction of differentiation were mostly incompatible events in individual cells, SCs were able to differentiate under conditions that also supported active proliferation. Overall, the results indicate that in the absence of neurons, cAMP can trigger SC re-differentiation concurrently with, but independently of, growth factor signaling. © 2008 Wiley-Liss, Inc. [source] Nitric Oxide-Induced Changes in Endothelial Expression of Phosphodiesterases 2, 3, and 5HEADACHE, Issue 3 2010Christoph J. Schankin MD (Headache 2010;50:431-441) Objective., To investigate nitric oxide (NO)-mediated changes in expression of cyclic nucleotide degrading phosphodiesterases 2A (PDE2A), PDE3B, and PDE5A in human endothelial cells. Background., Nitric oxide induces production of cyclic guanosine monophosphate (cGMP), which along with cyclic adenosine monophosphate (cAMP) is degraded by PDEs. NO donors and selective inhibitors of PDE3 and PDE5 induce migraine-like headache and play a role in endothelial dysfunction during stroke. The current study investigates possible NO modulation of cGMP-related PDEs relevant to headache induction in a cell line containing such PDEs. Methods., Real time polymerase chain reaction and Western blots were used to show expression of PDE2A, PDE3B, and PDE5A in a stable cell line of human brain microvascular endothelial cells. Effects of NO on PDE expression were analyzed at specific time intervals after continued DETA NONOate administration. Results., This study shows the expression of PDE2A, PDE3B, and PDE5A mRNA and PDE3B and PDE5A protein in human cerebral endothelial cells. Long-term DETA NONOate administration induced an immediate mRNA up-regulation of PDE5A (1.9-fold, 0.5 hour), an early peak of PDE2A (1.4-fold, 1 and 2 hours) and later up-regulation of both PDE3B (1.6-fold, 4 hours) and PDE2A (1.7-fold, 8 hours and 1.2-fold after 24 hours). Such changes were, however, not translated into significant changes in protein expression indicating few, if any, functional effects. Conclusions., Long-term NO stimulation modulated PDE3 and PDE5 mRNA expression in endothelial cells. However, PDE3 and PDE5 protein levels were unaffected by NO. The presence of PDE3 or PDE5 in endothelial cells indicates that selective inhibitors may have functional effects in such cells. A complex interaction of cGMP and cAMP in response to NO administration may take place if the mRNA translates into active protein. Whether or not this plays a role in the headache mechanisms remains to be investigated. [source] Fenofibrate differentially regulates plasminogen activator inhibitor-1 gene expression via adenosine monophosphate,activated protein kinase,dependent induction of orphan nuclear receptor small heterodimer partner,HEPATOLOGY, Issue 3 2009Dipanjan Chanda Plasminogen activator inhibitor type I (PAI-1) is a marker of the fibrinolytic system and serves as a possible predictor for hepatic metabolic syndromes. Fenofibrate, a peroxisome proliferator-activated receptor , (PPAR,) agonist, is a drug used for treatment of hyperlipidemia. Orphan nuclear receptor small heterodimer partner (SHP) plays a key role in transcriptional repression of crucial genes involved in various metabolic pathways. In this study, we show that fenofibrate increased SHP gene expression in cultured liver cells and in the normal and diabetic mouse liver by activating the adenosine monophosphate,activated protein kinase (AMPK) signaling pathway in a PPAR,-independent manner. Administration of transforming growth factor beta (TGF-,) or a methionine-deficient and choline-deficient (MCD) diet to induce the progressive fibrosing steatohepatitis model in C57BL/6 mice was significantly reversed by fenofibrate via AMPK-mediated induction of SHP gene expression with a dramatic decrease in PAI-1 messenger RNA (mRNA) and protein expression along with other fibrotic marker genes. No reversal was observed in SHP null mice treated with fenofibrate. Treatment with another PPAR, agonist, WY14643, showed contrasting effects on these marker gene expressions in wild-type and SHP null mice, demonstrating the specificity of fenofibrate in activating AMPK signaling. Fenofibrate exhibited a differential inhibitory pattern on PAI-1 gene expression depending on the transcription factors inhibited by SHP. Conclusion: By demonstrating that a PPAR,-independent fenofibrate-AMPK-SHP regulatory cascade can play a key role in PAI-1 gene down-regulation and reversal of fibrosis, our study suggests that various AMPK activators regulating SHP might provide a novel pharmacologic option in ameliorating hepatic metabolic syndromes. (HEPATOLOGY 2009.) [source] Rab4 facilitates cyclic adenosine monophosphate,stimulated bile acid uptake and Na+ -taurocholate cotransporting polypeptide translocation,HEPATOLOGY, Issue 5 2008Christopher M. Schonhoff Cyclic adenosine monophosphate (cAMP) stimulates hepatic bile acid uptake by translocating sodium-taurocholate (TC) cotransporting polypeptide (Ntcp) from an endosomal compartment to the plasma membrane. Rab4 is associated with early endosomes and involved in vesicular trafficking. This study was designed to determine the role of Rab4 in cAMP-induced TC uptake and Ntcp translocation. HuH-Ntcp cells transiently transfected with empty vector, guanosine triphosphate (GTP) locked dominant active Rab4 (Rab4(GTP)), or guanosine diphosphate (GDP) locked dominant inactive Rab4 (Rab4(GDP)) were used to study the role of Rab4. Neither Rab4(GTP) nor Rab4(GDP) affected either basal TC uptake or plasma membrane Ntcp level. However, cAMP-induced increases in TC uptake and Ntcp translocation were enhanced by Rab4(GTP) and inhibited by Rab4(GDP). In addition, cAMP increased GTP binding to endogenous Rab4 in a time-dependent, but phosphoinositide-3-kinase,independent manner. Conclusion: Taken together, these results suggest that cAMP-mediated phosphoinositide-3-kinase,independent activation of Rab4 facilitates Ntcp translocation in HuH-Ntcp cells. (HEPATOLOGY 2008.) [source] Glucagon induces the plasma membrane insertion of functional aquaporin-8 water channels in isolated rat hepatocytesHEPATOLOGY, Issue 6 2003Sergio A. Gradilone Although glucagon is known to stimulate the cyclic adenosine monophosphate (cAMP)-mediated hepatocyte bile secretion, the precise mechanisms accounting for this choleretic effect are unknown. We recently reported that hepatocytes express the water channel aquaporin-8 (AQP8), which is located primarily in intracellular vesicles, and its relocalization to plasma membranes can be induced with dibutyryl cAMP. In this study, we tested the hypothesis that glucagon induces the trafficking of AQP8 to the hepatocyte plasma membrane and thus increases membrane water permeability. Immunoblotting analysis in subcellular fractions from isolated rat hepatocytes indicated that glucagon caused a significant, dose-dependent increase in the amount of AQP8 in plasma membranes (e.g., 102% with 1 ,mol/L glucagon) and a simultaneous decrease in intracellular membranes (e.g., 38% with 1 ,mol/L glucagon). Confocal immunofluorescence microscopy in cultured hepatocytes confirmed the glucagon-induced redistribution of AQP8 from intracellular vesicles to plasma membrane. Polarized hepatocyte couplets showed that this redistribution was specifically to the canalicular domain. Glucagon also significantly increased hepatocyte membrane water permeability by about 70%, which was inhibited by the water channel blocker dimethyl sulfoxide (DMSO). The inhibitors of protein kinase A, H-89, and PKI, as well as the microtubule blocker colchicine, prevented the glucagon effect on both AQP8 redistribution to hepatocyte surface and cell membrane water permeability. In conclusion, our data suggest that glucagon induces the protein kinase A and microtubule-dependent translocation of AQP8 water channels to the hepatocyte canalicular plasma membrane, which in turn leads to an increase in membrane water permeability. These findings provide evidence supporting the molecular mechanisms of glucagon-induced hepatocyte bile secretion. [source] Defective regulation of cholangiocyte Cl,/HCO,3 and Na+/H+ exchanger activities in primary biliary cirrhosisHEPATOLOGY, Issue 6 2002Saida Melero Primary biliary cirrhosis (PBC) is a disorder of unknown origin with autoimmune features. Recently, impaired biliary secretion of bicarbonate has been shown in patients with PBC. Here we have investigated whether bile duct epithelial cells isolated from PBC patients exhibit defects in transepithelial bicarbonate transport by analyzing the activities of 2 ion exchangers, Cl,/HCO,3 anion exchanger 2 (AE2) and Na+/H+ exchanger (NHE) in isolated cholangiocytes. AE2 and NHE activities were studied in basal conditions and after stimulation with cyclic adenosine monophosphate (cAMP) and extracellular adenosine triphosphate (ATP), respectively. Cholangiocytes were grown from needle liver biopsies from 12 PBC patients, 8 normal controls, and 9 patients with other liver diseases. Also, intrahepatic cholangiocytes were cultured after immunomagnetic isolation from normal liver tissue (n = 6), and from recipients undergoing liver transplantation for end-stage PBC (n = 9) and other forms of liver disease (n = 8). In needle-biopsy cholangiocytes, basal AE2 activity was significantly decreased in PBC as compared with normal livers and disease controls. In addition, we observed that though cAMP increased AE2 activity in cholangiocytes from both normal and non-PBC livers, this effect was absent in PBC cholangiocytes. Similarly, though in cholangiocytes from normal and disease control livers extracellular ATP induced a marked enhancement of NHE activity, cholangiocytes from PBC patients failed to respond to purinergic stimulation. In conclusion, our findings provide functional evidence that PBC cholangiocytes exhibit a widespread failure in the regulation of carriers involved in transepithelial H+/HCO,3 transport, thus, providing a molecular basis for the impaired bicarbonate secretion in this cholestatic syndrome. [source] Regulation of human neutrophil-mediated cartilage proteoglycan degradation by phosphatidylinositol-3-kinaseIMMUNOLOGY, Issue 1 2001C. S. T. Hii Summary The ability of neutrophils to degrade cartilage proteoglycan suggests that the neutrophils that accumulate in the joints of rheumatoid arthritis patients are mediators of tissue damage. The regulatory mechanisms which are relevant to the proteoglycan-degrading activity of neutrophils are poorly understood. Since phosphatidylinositol 3-kinase (PI3-K), protein kinase C (PKC), the extracellular signal-regulated protein kinase (ERK)1/ERK2 and cyclic adenosine monophosphate (cAMP) have been reported to regulate neutrophil respiratory burst and/or degranulation, a role for these signalling molecules in regulating proteoglycan degradation was investigated. Preincubation of human neutrophils with GF109203X (an inhibitor of PKC), PD98059 (an inhibitor of MEK, the upstream regulator of ERK1/ERK2) or with forskolin or dibutyryl cAMP, failed to suppress proteoglycan degradation of opsonized bovine cartilage. In contrast, preincubation of neutrophils with wortmannin or LY294002, specific inhibitors of PI3-K, inhibited proteoglycan degradation. Incubation of neutrophils with cartilage resulted in the activation of PI3-K in neutrophils, consistent with a role for PI3-K in proteoglycan degradation. Activation of PI3-K and proteoglycan degradation was enhanced by tumour necrosis factor-,. Degradation caused by neutrophils from the synovial fluid of rheumatoid arthritis patients was also inhibited by wortmannin. These data demonstrate that the proteoglycan degradative activity of neutrophils required PI3-K but not PKC or the ERK1/ERK2/ERK5 cascades and was insensitive to increases in intracellular cAMP concentrations. [source] Functional expression of a locust tyramine receptor in murine erythroleukaemia cellsINSECT MOLECULAR BIOLOGY, Issue 6 2001J. Poels Abstract The LCR/MEL system (Locus Control Region/Murine Erythroleukaemia cells) was employed to express and characterize the Locusta migratoria tyramine receptor (TyrLoc), an insect G protein-coupled receptor. Functional agonist-dependent responses were recorded in stable, tyramine receptor expressing cell clones (MEL-TyrLoc). Tyramine elicited a dose-dependent increase of cytosolic Ca2+ -ions and an attenuation of forskolin-induced cyclic adenosine monophosphate (AMP) production. Octopamine was shown to be a weak agonist for both responses. In addition, yohimbine proved to be a potent tyramine receptor antagonist. This study reports the first application of the LCR/MEL expression system in functional assays for G protein-coupled receptors and therefore expands the capabilities of this system by exploiting the functionality of the signal transduction pathways. [source] TERMINATION OF PUPAL DIAPAUSE IN THE BOLLWORM HELICOVERPA ARMIGERA BY PRECOCENE IIINSECT SCIENCE, Issue 4 2001WANG Fang-hai Abstract Precocene II terminated pupal diapause in the bollworm Helicoverpa armigera as 20-hydroxyecdysterone did, whereas juvenile hormone analog ZR-515, cyclic adenosine monophosphate (CAMP), and 5-hydroxytryptamine (5-HT) did not. The results indicate that precocene II affects diapausing pupae in the similar way as what was found in the prepupae of the aphid parasitoids, Aphidius matricariae Haliday and Praon volucre Haliday (Hymenoptera: Aphidiidae). It is suggested that precocene II may affect different kinds of termination of diapause in insects. [source] ORIGINAL ARTICLE: The approach to the mechanism of calcitonin gene-related peptide-inducing inhibition of food intakeJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 5 2010J.-Y. Sun Summary The aim of this study was to investigate the anorectic mechanism of calcitonin gene-related peptide (CGRP) in rats. Intraperitoneal injection of CGRP (50 ,g/kg) resulted in decline (p < 0.05) in the food intake of rats at 0.5, 1, 2 and 4 h in comparison with saline control. Compared with saline-treated group, the levels of hypothalamic 3,,5,-cyclic adenosine monophosphate (cAMP) and plasma glucagon were increased (p < 0.05) in CGRP-treated group, but insulin level was decreased (p < 0.05). No significant changes (p > 0.05) in the plasma leptin were observed between two treatment groups. Calcitonin gene-related peptide injection down regulated (p < 0.05) both neuropeptide Y (NPY) and melanin-concentrating hormone (MCH) genes at mRNA levels, but up regulated (p < 0.05) the expression of cholecystokinin (CCK) gene. The correlations analysis showed that food intake was negatively correlated (p < 0.05) with CCK mRNA, cAMP and glucagon levels. Moreover, there existed negative correlations (p < 0.05) between MCH mRNA and glucagon levels, and positive correlations (p < 0.05) between insulin and leptin levels. The results showed that cAMP acting as the second messenger may play a vital role in the anorectic effects of CGRP. Calcitonin gene-related peptide could stimulate anorexigenic neuropeptides (i.e. CCK) and/or inhibit orexigenic neuropeptides (i.e. NPY and MCH) expression, and ultimately suppressed food intake that was functionally coupled to cAMP/PKA pathway activation. [source] Induction of Transcriptional Activity of the Cyclic Adenosine Monophosphate Response Element Binding Protein by Parathyroid Hormone and Epidermal Growth Factor in Osteoblastic Cells,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2002John T. Swarthout Abstract Previously, we have shown that parathyroid hormone (PTH) transactivation of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) requires both serine 129 (S129) and serine 133 (S133) in rat osteosarcoma cells UMR 106-01 (UMR) cells. Furthermore, although protein kinase A (PKA) is responsible for phosphorylation at S133, glycogen synthase kinase 3, (GSK-3,) activity is required and may be responsible for phosphorylation of CREB at S129. Here, we show, using the GAL4-CREB reporter system, that epidermal growth factor (EGF) can transactivate CREB in UMR cells in addition to PTH. Additionally, treatment of UMR cells with both PTH and EGF results in greater than additive transactivation of CREB. Furthermore, using mutational analysis we show that S129 and S133 are required for EGF-induced transcriptional activity. EGF activates members of the MAPK family including p38 and extracellular signal,activated kinases (ERKs), and treatment of UMR cells with either the p38 inhibitor (SB203580) or the MEK inhibitor (PD98059) prevents phosphorylation of CREB at S133 by EGF but not by PTH. Treatment of cells with either SB203580 or PD98059 alone or together significantly inhibits transactivation of CREB by EGF but not by PTH, indicating that EGF regulates CREB phosphorylation and transactivation through p38 and ERKs and PTH does not. Finally, the greater than additive transactivation of CREB by PTH and EGF is significantly inhibited by the PKA inhibitor H-89 or by cotreatment with SB203580 and PD98059. Thus, several different signaling pathways in osteoblastic cells can converge on and regulate CREB activity. This suggests, in vivo, that circulating agents such as PTH and EGF are acting in concert to exert their effects. [source] Direct Measurement of Hormone-Induced Acidification in Intact BoneJOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2000Glenn S. Belinsky Abstract Previous findings have shown that osteoblasts respond to parathyroid hormone (PTH) with an increase in extracellular acidification rate (ECAR) in addition to the known effect of PTH to increase local acidification by osteoclasts. We, therefore, investigated use of the Cytosensor to measure the ECAR response of whole intact bone to PTH employing microphysiometry. The Cytosensor measures a generic metabolic increase of cells to various agents. Using neonatal mouse calvaria, we found that the area surrounding the sagittal suture was particularly responsive to PTH. In this bone, the increase in ECAR was slower to develop (6 minutes) and more persistent than in cultured human osteoblast-like SaOS-2 cells and was preceded by a brief decrease in ECAR Salmon calcitonin also produced an increase in ECAR in this tissue but with a different pattern than that elicited by PTH. Because PTH stimulates osteoclastic bone resorption in mouse calvaria via a cyclic adenosine monophosphate (cAMP)-mediated mechanism, we showed that the adenylyl cyclase activator forskolin also stimulated ECAR in this tissue. When the protein kinase A (PKA) pathway was activated by maintaining a high intracellular concentration of cAMP using N6 -2,-0-dibutyryladenosine-cAMP (db-cAMP), there was a reduction of PTH-induced acidification, while isobutylmethylxanthine pretreatment potentiated the PTH-induced acidification, consistent with a PKA-mediated pathway. Thapsigargin and the protein kinase C (PKC) activator phorbol myristate acetate had no effect on the PTH-induced increase in ECAR in calvaria, indicating that PKC does not play a major role in the ECAR response in intact bone. These results indicate the utility of using microphysiometry to study ECAR responses in intact tissue and should enable elucidation of the relative importance of extracellular acidification by osteoblasts and osteoclasts to the anabolic and catabolic activities of PTH, respectively. [source] Calculation of relative binding affinities of fructose 1,6-bisphosphatase mutants with adenosine monophosphate using free energy perturbation methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2007Ravichandra Mutyala Abstract The free energy perturbation (FEP) methodology is the most accurate means of estimating relative binding affinities between inhibitors and protein variants. In this article, the importance of hydrophobic and hydrophilic residues to the binding of adenosine monophosphate (AMP) to the fructose 1,6-bisphosphatase (FBPase), a target enzyme for type-II diabetes, was examined by FEP method. Five mutations were made to the FBPase enzyme with AMP inhibitor bound: 113Tyr , 113Phe, 31Thr , 31Ala, 31Thr , 31Ser, 177Met , 177Ala, and 30Leu , 30Phe. These mutations test the strength of hydrogen bonds and van der Waals interactions between the ligand and enzyme. The calculated relative free energies indicated that: 113Tyr and 31Thr play an important role, each via two hydrogen bonds affecting the binding affinity of inhibitor AMP to FBPase, and any changes in these hydrogen bonds due to mutations on the protein will have significant effect on the binding affinity of AMP to FBPase, consistent to experimental results. Also, the free energy calculations clearly show that the hydrophilic interactions are more important than the hydrophobic interactions of the binding pocket of FBPase. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Oxidative stress: A cause and therapeutic target of diabetic complicationsJOURNAL OF DIABETES INVESTIGATION, Issue 3 2010Eiichi Araki Abstract Oxidative stress is defined as excessive production of reactive oxygen species (ROS) in the presence of diminished anti-oxidant substances. Increased oxidative stress could be one of the common pathogenic factors of diabetic complications. However, the mechanisms by which hyperglycemia increases oxidative stress are not fully understood. In this review, we focus on the impact of mitochondrial derived ROS (mtROS) on diabetic complications and suggest potential therapeutic approaches to suppress mtROS. It has been shown that hyperglycemia increases ROS production from mitochondrial electron transport chain and normalizing mitochondrial ROS ameliorates major pathways of hyperglycemic damage, such as activation of polyol pathway, activation of PKC and accumulation of advanced glycation end-products (AGE). Additionally, in subjects with type 2 diabetes, we found a positive correlation between HbA1c and urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG), which reflects mitochondrial oxidative damage, and further reported that 8-OHdG was elevated in subjects with diabetic micro- and macro- vascular complications. We recently created vascular endothelial cell-specific manganese superoxide dismutase (MnSOD) transgenic mice, and clarified that overexpression of MnSOD in endothelium could prevent diabetic retinopathy in vivo. Furthermore, we found that metformin and pioglitazone, both of which have the ability to reduce diabetic vascular complications, could ameliorate hyperglycemia-induced mtROS production by the induction of PPAR, coactivator-1, (PGC-1,) and MnSOD and/or activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK). We also found that metformin and pioglitazone promote mitochondrial biogenesis through the same AMPK,PGC-1, pathway. Taking these results, mtROS could be the key initiator of and a therapeutic target for diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00013.x, 2010) [source] EFFECT OF HIGH PRESSURE TREATMENT ON CYTOPLASMIC 5,-NUCLEOTIDASE FROM RABBIT SKELETAL MUSCLEJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2007SUNAO MORI ABSTRACT We investigated the effect of high-pressure treatment on the properties of cytoplasmic 5, -nucleotidase (NT), which converts inosine monophosphate (IMP) into inosine. After pressure treatment at 400 MPa, the activity of purified IMP-NT remained at almost 100%, but the activity of partially purified adenosine monophosphate (AMP)-NT decreased to about 40%. These data suggest that there is a difference in the pressure stability between the enzymes. In situ fluorescence spectroscopy of IMP-NT under pressure showed that its pressure-induced denaturation was reversible. When the pressure was reduced from the highest pressure to ambient pressure, hysteresis was observed. This suggests that high pressure treatment may lead to a partial change in the affinity of the subunits for each other once they have dissociated. The activities of IMP-NT and AMP-NT extracted from pressure-treated muscles decreased remarkably between 250 and 450 MPa, but IMP-NT was more stable than AMP-NT. [source] The Effects of Disruption of A Kinase Anchoring Protein,Protein Kinase A Association on Protein Kinase A Signalling in Neuroendocrine Melanotroph Cells of Xenopus laevisJOURNAL OF NEUROENDOCRINOLOGY, Issue 7 2006G. J. H. Corstens Abstract The secretory activity of melanotroph cells from Xenopus laevis is regulated by multiple neurotransmitters that act through adenylyl cyclase. Cyclic adenosine monophosphate (cAMP), acting on protein kinase A (PKA), stimulates the frequency of intracellular Ca2+ oscillations and the secretory activity of the melanotroph cell. Anchoring of PKA near target proteins is essential for many PKA-regulated processes, and the family of A kinase anchoring proteins (AKAPs) is involved in the compartmentalisation of PKA type II (PKA II) regulatory subunits. In the present study, we determined to what degree cAMP signalling in Xenopus melanotrophs depends on compartmentalised PKA II. For this purpose, a membrane-permeable stearated form of Ht31 (St-Ht31), which dislodges PKA II from AKAP (thus disrupting PKA II signalling), was used. The effect of St-Ht31 on both secretion of radiolabelled peptides and intracellular Ca2+ signalling by superfused Xenopus melanotrophs was assessed. St-Ht31 stimulated secretion but had no effect on Ca2+ signalling. We conclude Xenopus melanotrophs possess a St-Ht31-sensitive PKA II that is associated with the exocytosis machinery and, furthermore, that Ca2+ signalling is regulated by an AKAP-independent signalling system. Moreover, our results support a recent proposal that AKAP participates in regulating PKA activity independently from cAMP. [source] Dependence of Hyperpolarisation-Activated Cyclic Nucleotide-Gated Channel Activity on Basal Cyclic Adenosine Monophosphate Production in Spontaneously Firing GH3 CellsJOURNAL OF NEUROENDOCRINOLOGY, Issue 7 2006K. Kretschmannova Abstract The hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels play a distinct role in the control of membrane excitability in spontaneously active cardiac and neuronal cells. Here, we studied the expression and role of HCN channels in pacemaking activity, Ca2+ signalling, and prolactin secretion in GH3 immortalised pituitary cells. Reverse transcriptase-polymerase chain reaction analysis revealed the presence of mRNA transcripts for HCN2, HCN3 and HCN4 subunits in these cells. A hyperpolarisation of the membrane potential below ,,60 mV elicited a slowly activating voltage-dependent inward current (Ih) in the majority of tested cells, with a half-maximal activation voltage of ,89.9 ± 4.2 mV and with a time constant of 1.4 ± 0.2 s at ,120 mV. The bath application of 1 mM Cs+, a commonly used inorganic blocker of Ih, and 100 µM ZD7288, a specific organic blocker of Ih, inhibited Ih by 90 ± 4.1% and 84.3 ± 1.8%, respectively. Receptor- and nonreceptor-mediated activation of adenylyl and soluble guanylyl cyclase and the addition of a membrane permeable cyclic adenosine monophosphate (cAMP) analogue, 8-Br-cAMP, did not affect Ih. Inhibition of basal adenylyl cyclase activity, but not basal soluble guanylyl cyclase activity, led to a reduction in the peak amplitude and a leftward shift in the activation curve of Ih by 23.7 mV. The inhibition of the current was reversed by stimulation of adenylyl cyclase with forskolin and by the addition of 8-Br-cAMP, but not 8-Br-cGMP. Application of Cs+ had no significant effect on the resting membrane potential or electrical activity, whereas ZD7288 exhibited complex and Ih -independent effects on spontaneous electrical activity, Ca2+ signalling, and prolactin release. These results indicate that HCN channels in GH3 cells are under tonic activation by basal level of cAMP and are not critical for spontaneous firing of action potentials. [source] Analysis of neural potential of human umbilical cord blood,derived multipotent mesenchymal stem cells in response to a range of neurogenic stimuliJOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2008Isabel Zwart Abstract We investigated the neurogenic potential of full-term human umbilical cord blood (hUCB),derived multipotent mesenchymal stem cells (MSCs) in response to neural induction media or coculture with rat neural cells. Phenotypic and functional changes were assessed by immunocytochemistry, RT-PCR, and whole-cell patch-clamp recordings. Naive MSCs expressed both mesodermal and ectodermal markers prior to neural induction. Exposure to retinoic acid, basic fibroblast growth factor, or cyclic adenosine monophosphate (cAMP) did not stimulate neural morphology, whereas exposure to dibutyryl cAMP and 3-isobutyl-1-methylxanthine stimulated a neuron-like morphology but also appeared to be cytotoxic. All protocols stimulated increases in expression of the neural precursor marker nestin, but expression of mature neuronal or glial markers MAP2 and GFAP was not observed. Nestin expression increases were serum level dependent. Electrophysiological properties of MSCs were studied with whole-cell patch-clamp recordings. The MSCs possessed no ionic currents typical of neurons before or after neural induction protocols. Coculture of hUCB-derived MSCs and rat neural cells induced some MSCs to adopt an astrocyte-like morphology and express GFAP protein and mRNA. Our data suggest hUCB-derived MSCs do not transdifferentiate into mature functioning neurons in response to the above neurogenic protocols; however, coculture with rat neural cells led to a minority adopting an astrocyte-like phenotype. © 2008 Wiley-Liss, Inc. [source] "Soluble" adenylyl cyclase-generated cyclic adenosine monophosphate promotes fast migration in PC12 cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2008Jennifer J. Young Abstract In a model for neuronal movement, PC12 cells undergo fast migration in response to nerve growth factor (NGF) and phorbol ester (PMA). We previously showed that NGF increases intracellular cAMP via activation of soluble adenylyl cyclase (sAC). In this report, we demonstrate that sAC activation is an essential component of NGF- + PMA-induced fast migration in PC12 cells. Interestingly, PMA also raises intracellular cAMP but does so by stimulating transmembrane adenylyl cyclases (tmAC); however, this tmAC-generated cAMP does not contribute to fast migration. Therefore, cells must possess independent pools of cAMP capable of modulating distinct functions. © 2007 Wiley-Liss, Inc. [source] Phosphorylation of the nicotinic acetylcholine receptor in myotube-cholinergic neuron coculturesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Maria A. Lanuza Abstract Acetylcholine receptor (AChR) stability in the postsynaptic membrane is affected by serine kinases. AChR are phosphorylated by protein kinase C (PKC) and PKA, and we have shown that activation of PKA and PKC have opposite effects on AChR stability and that this may play some role in the selective, activity-dependent synapse loss that occurs during development of the neuromuscular junction. Myotube cultures with and without added spinal motor neurons were probed with immunoaffinity-purified antibodies prepared against phosphorylated peptides with amino acid sequences from different AChR subunits. Different treatments activating PKC (phorbol 12-myristate 13-acetate; PMA) or PKA (dibutyryl cyclic adenosine monophosphate; cAMP) or blocking electrical activity (tetrodotoxin; TTX) of the cocultures were chosen because of their known effects, direct or indirect, on receptor stability. We asked whether the phospho-specific antibody staining in conjunction with ,-bungarotoxin (BTX) identification of AChR aggregates could provide a direct demonstration of changes in receptor phosphorylation produced by the treatments. We found that PMA treatment did increase phosphorylation of the delta subunit and cAMP increased phosphorylation of the epsilon subunit relative to total BTX labeling in muscle-nerve cocultures, but not in muscle-only cultures. Blockade of electrical activity with TTX increased the incidence of aggregates that showed no phospho-epsilon staining. Myotube cultures grown in the absence of neurons did not show the responses of myotubes in cocultures. The results show that manipulations that alter receptor stability also produce changes in receptor phosphorylation. We suggest that phosphorylation may be a mechanism mediating the changes in receptor stability. © 2006 Wiley-Liss, Inc. [source] Modulation of perch connexin35 hemi-channels by cyclic AMP requires a protein kinase A phosphorylation siteJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003Georgia Mitropoulou Abstract Retinal neurons are coupled via gap junctions, which function as electrical synapses that are gated by ambient light conditions. Gap junctions connecting either horizontal cells or AII amacrine cells are inhibited by the neurotransmitter dopamine, via the activation of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway. Fish connexin35 (Cx35) and its mouse ortholog, Cx36, are good candidates to undergo dopaminergic modulation, because they have been detected in the inner plexiform layer of the retina, where Type II amacrine cells establish synaptic contacts. We have taken advantage of the ability of certain connexins to form functional connexons (hemi-channels), when expressed in Xenopus oocytes, to investigate whether pharmacological elevation of cAMP modulates voltage-activated hemi-channel currents in single oocytes. Injection of perch Cx35 RNA into Xenopus oocytes induced outward voltage-dependent currents that were recorded at positive membrane potentials. Incubation of oocytes with 8-bromoadenosine 3,,5,-cyclic monophosphate (8-Br-cAMP), a membrane permeable cAMP analog, resulted in a dose-dependent and reversible inhibition of hemi-channel currents at the more positive voltage steps. In contrast, treatment with 8-Br-cAMP did not have any effect on hemi-channel currents induced by skate Cx35. Amino acid sequence comparison of the two fish connexins revealed, in the middle cytoplasmic loop of perch Cx35, the presence of a PKA consensus sequence that was absent in the skate connexin. The results obtained with two constructs in which the putative PKA phosphorylation site was either suppressed (perch Cx35R108Q) or introduced (skate Cx35Q108R) indicate that it is responsible for the inhibition of hemi-channel currents. These studies demonstrate that perch Cx35 is a target of the cAMP/PKA signaling pathway and identify a consensus PKA phosphorylation site that is required for channel gating. © 2003 Wiley-Liss, Inc. [source] Investigation of ,2 -adrenoceptor subtype selectivity and organ specificity for bedoradrine (KUR-1246), a novel tocolytic beta-adrenergic receptor stimulantJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 3 2009Yoshihito Inoue Abstract Objectives:, The aim of this study was to evaluate the beta-adrenergic receptor (,-AR) selectivity, organ specificity and efficacy of delaying the onset of spontaneous delivery of bedoradrine (KUR-1246), a novel uterine relaxant. Methods:, ,-AR selectivity was evaluated in terms of the amount of cyclic adenosine monophosphate produced by bedoradrine, ritodrine and isoprenaline in Chinese hamster ovary cells expressing human ,1 -, ,2 -AR or ,3 -AR. Inhibition of contractions of the atrium, trachea and proximal colon by bedoradrine were compared with those of the uterus in pregnant rats using an organ bath method. Finally, the delaying effect of bedoradrine on spontaneous labor was evaluated by an in vivo study using term pregnant rats. Results:, EC50 values of bedoradrine for cyclic adenosine monophosphate production in Chinese hamster ovary cells via ,1 -, ,2 - and ,3 -AR were 2400 ± 30, 2.9 ± 0.10 and 363 ± 3 nmol/L, respectively, indicating that bedoradrine had 832- and 126-fold higher selectivity for ,2 -AR than for ,1 - and ,3 -AR. EC50 values of bedoradrine for the uterus, atrium, trachea and proximal colon were 1.01 ± 0.27, 2300 ± 356, 1610 ± 299 and 219 ± 23.5 nmol/L, respectively. Thus, bedoradrine was 2280-, 1590- and 217-fold more specific for the uterus than for the atrium, trachea and proximal colon, respectively. Bedoradrine delayed the spontaneous delivery of 21-day-pregnant rats in a dose-dependent manner. Conclusions:, Bedoradrine is a promising drug for the treatment of preterm labor in obstetrical practice because it has better selectivity for ,2 -AR and specificity for the uterus than currently used agents and may effectively delay spontaneous delivery. [source] Tocolytic Effects of a Long-acting ,2 -Adrenoceptor Agonist, Formoterol, in RatsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2000NORIHIRO SHINKAI We have assessed the tocolytic activity of formoterol, a novel long-acting and potent ,2 -adrenoceptor agonist, through its production of cyclic adenosine monophosphate, in comparison with ritodrine, a ,2 -adrenoceptor agonist used clinically to counter premature delivery. Formoterol and ritodrine inhibited the amplitude and frequency of rat uterine contraction, with IC50 values of 3.8 times 10,10 and 4.7 times 10,7 M, respectively. Intravenous administration of formoterol or ritodrine caused inhibition of uterine motility and increased heart rate in a dose-dependent manner. Inhibition of uterine motility by oral administration of formoterol (0.3 and 1 mg kg,1) continued for at least 60 min, whereas that with ritodrine (100 mg kg,1) persisted for 15 min with rapid recovery thereafter in pregnant rats. The ,-adrenoceptor binding of [125I]iodopindolol to the myometrium of pregnant rats was competitive with formoterol and ritodrine, with Ki values of 0.04 and 6.10 nM, respectively. Formoterol (10,6 , 10,4 M) and ritodrine (10,6 , 10,4 M) increased the level of cyclic adenosine monophosphate in lymphocytes in a dose-dependent manner. The results suggested that formoterol caused relaxation of uterine motility through production of cyclic adenosine monophosphate. Thus, formoterol may be useful as a treatment to counter premature delivery. [source] Ranolazine Attenuates Palmitoyl- l -carnitine-induced Mechanical and Metabolic Derangement in the Isolated, Perfused Rat HeartJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2000KAZUYASU MARUYAMA The effect of ranolazine, a novel anti-ischaemic drug that stimulates the activity of pyruvate dehydrogenase, on palmitoyl- l -carnitine-induced mechanical dysfunction and metabolic derangement in isolated perfused rat hearts has been studied and compared with the effect of dichloroacetate, an activator of pyruvate dehydrogenase. Rat hearts paced electrically were perfused aerobically at constant flow by the Langendorff technique. Palmitoyl- l -carnitine (4 ,m) increased left ventricular end-diastolic pressure and reduced left ventricular developed pressure (i.e. induced mechanical dysfunction); it also reduced tissue levels of adenosine triphosphate and increased tissue levels of adenosine monophosphate (i.e. induced metabolic derangement). These functional and metabolic alterations induced by palmitoyl- l -carnitine were attenuated by ranolazine (5, 10, and 20 ,m) in a concentration-dependent manner. In contrast, dichloroacetate (1 and 10 mm) did not attenuate palmitoyl- l -carnitine-induced mechanical and metabolic derangement. In the normal (palmitoyl- l -carnitine-untreated) heart, however, ranolazine did not modify mechanical function and energy metabolism. These results suggest that ranolazine attenuates palmitoyl- l -carnitine-induced mechanical and metabolic derangement in the rat heart, and that the beneficial action of ranolazine is not because of the energy-sparing effect or activation of pyruvate dehydrogenase. [source] | |||||||||||||||||||||||||||||||||||||