title: Signal transduction mechanism(s) involved in prostacyclin production elicited by acetylcholine in coronary endothelial cells of rabbit heart.
abstract: The purpose of this study was to elucidate the mechanism by which acetylcholine (ACh) promotes prostacyclin (PGI2) production in cultured coronary endothelial cells (CEC) of the rabbit heart. ACh-induced production of PGI2, measured as immunoreactive 6-keto-PGF1alpha, was enhanced by increasing the extracellular calcium (Ca++) concentration and reduced by Ca++ depletion. The receptor-operated Ca++ channel blocker SK&F96365, but not the voltage-dependent Ca++ channel blockers verapamil or nifedipine, attenuated ACh-induced 6-keto-PGF1alpha production and the associated rise in cytosolic Ca++. Thapsigargin, which depleted Ca++ accumulation from the intracellular Ca++ store, did not prevent the ACh-induced rise in cytosolic Ca++. In the absence of extracellular Ca++, ACh and ATP increased cytosolic Ca++ but did not alter 6-keto-PGF1alpha production. In permeabilized CEC, guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) but not ACh enhanced 6-keto-PGF1alpha synthesis. ACh increased 6-keto-PGF1alpha production in the presence of GTP-gamma-S. These effects of GTP-gamma-S were attenuated by guanosine 5'-O-(2-thiotriphosphate). In the absence of extracellular Ca++, ACh or ATP increased cytosolic Ca++ in cells permeabilized with beta-escin and loaded with GTP-gamma-S; this effect was attenuated by guanosine 5'-O-(2-thiotriphosphate). The effect of ATP but not ACh to mobilize intracellular Ca++ or increase 6-keto-PGF1alpha was inhibited by pertussis toxin. The phospholipase C inhibitor D609, which attenuated ACh- and ATP-induced mobilization of intracellular Ca++, did not alter 6-keto-PGF1alpha production. The NO synthase inhibitor N-monomethyl-arginine also failed to alter ACh-induced 6-keto-PGF1alpha synthesis. These data suggest that, in CEC of the rabbit heart, ACh stimulates prostacyclin production via a pertussis toxin-insensitive G protein and by increasing the influx of extracellular Ca++ through a G protein-independent receptor-operated Ca++ channel.
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Center for the Health Sciences, Memphis 38163, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kan
authors.forename: Y
authors.initials: Y
authors.lastname: Ruan
authors.forename: K U
authors.initials: KU
authors.lastname: Malik
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D011464:Epoprostenol / Q000096:biosynthesis*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D037342:Pertussis Toxin; D011817:Rabbits; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010566:Virulence Factors, Bordetella; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019284:Thapsigargin; D011464:Epoprostenol; D037342:Pertussis Toxin; D009543:Nifedipine; D000109:Acetylcholine; D002118:Calcium