title: Insulin inhibits coronary endothelial cell calcium entry and coronary artery relaxation.
abstract: Hyperinsulinemia is closely related to coronary artery disease. Endothelial cells are important for the control of vascular tone, and dysfunction of endothelial cells has been implicated in coronary artery disease. The direct effects of insulin on coronary endothelial cells are nonetheless unknown. In this study, the acute effects of high-dose insulin were investigated on agonist-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) in porcine coronary endothelial cells and coronary relaxation. Bradykinin (10 n M ) and cyclopiazonic acid (100 microM), an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, provoked large increases in [Ca(2+)](i) in coronary endothelial cells. This increase was dose-dependently inhibited by a 10-min preincubation with high doses of insulin (10, 30, 100 mU/ml). Under Ca(2+)-free conditions, bradykinin and cyclopiazonic acid provoked transient, small increases in [Ca(2+)](i). These increases were not affected by pretreatment with insulin (100 mU/ml). Bradykinin (1, 10, 100, 1,000 n M ) and cyclopiazonic acid (10 microM) significantly relaxed porcine coronary artery rings precontracted with histamine (1 microM). The vasodilator effects of bradykinin and cyclopiazonic acid were dose-dependently inhibited by insulin. These acute effects were not observed at physiologic concentrations. Our data indicate that high-dose insulin inhibits agonist-induced Ca(2+) response in coronary endothelial cells and attenuates agonist-induced coronary vasodilatation. The study suggests that hyperinsulinemia might be associated with coronary artery disease via derangement of endothelial Ca(2+)-dependent functions.
authors.affiliation: Department of Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan.
authors.forename: Q K
authors.initials: QK
authors.lastname: Tran
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
authors.forename: H Y
authors.initials: HY
authors.lastname: Le
authors.forename: K
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Hattori
authors.forename: H
authors.initials: H
authors.lastname: Tomioka
authors.forename: K
authors.initials: K
authors.lastname: Ohashi
authors.forename: H
authors.initials: H
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000037:antagonists & inhibitors; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000502:physiology*; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D007211:Indoles / Q000037:antagonists & inhibitors; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D013552:Swine; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000037:antagonists & inhibitors
chemical_list: D007004:Hypoglycemic Agents; D007211:Indoles; D007328:Insulin; D014665:Vasodilator Agents; D001920:Bradykinin; D002118:Calcium; C000543:cyclopiazonic acid