title: Modulatory role of endothelial calcium level in vascular tension of canine depolarized coronary arteries.
abstract: The vascular tension in the coronary artery is modulated by factors released by endothelial cells. We investigated the relationship between the Ca2+ level in endothelium and endothelium-mediated changes in smooth muscle tone in high K(+)-depolarized canine coronary arteries by measuring intracellular Ca2+ concentration fluorimetrically with the Ca2+ indicator fura 2. Addition of Ca2+ (1 mM) caused an increase in endothelial Ca2+ and relaxed the 30 mM K(+)-depolarized arteries following inhibition of Ca2+ influx in the smooth muscle with diltiazem. This relaxation was inhibited by NG-monomethyl-L-arginine. As extracellular K+ concentration was decreased, increases of endothelial Ca2+ were augmented, whereas the relaxation was decreased. Basal muscle tone was found to be decreased in low K+ by measuring relaxation by sodium nitroprusside. These results suggest the importance of Ca2+ level in the endothelium in playing a modulatory role in coronary tension through the production of nitric oxide. The correlation of extracellular K+ to Ca2+ level in the endothelium indicates a typical characteristic of the passive Ca2+ entry pathway in the endothelium, whereas the resultant relaxation appears to be restricted by the basal muscle tone.
authors.affiliation: Laboratory of Pharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.forename: J
authors.initials: J
authors.lastname: Yamazaki
authors.forename: T
authors.initials: T
authors.lastname: Nagao
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D011189:Potassium Chloride; D019001:Nitric Oxide Synthase; D004110:Diltiazem; D000109:Acetylcholine; D002118:Calcium