Glibenclamide, a specific inhibitor of ATP-sensitive K+ channels, inhibits coronary vasodilation induced by angiotensin II-receptor antagonists.
The purpose of our study was test the hypothesis that endogenous angiotensin II contributes to the basal coronary artery tone by acting at vascular ATP-sensitive K+ (K+ATP) channels. Coronary blood flow (CBF) and other hemodynamic parameters were measured in anesthetized dogs. Intracoronary infusion of the selective antagonists of angiotensin II AT1 receptors (L-158,809 and E4177) increased CHF without affecting other hemodynamic parameters, indicating that endogenous angiotensin II caused coronary vaso-constriction through the AT1 subtype receptors. Coronary vasodilation in response to AT1 receptor antagonists was blunted by pretreatment with glibenclamide (a specific inhibitor of K+ATP channels; p < 0.01) but not by either an adenosine-receptor antagonist or an inhibitor of nitric oxide synthesis. Coronary vasodilation in response to AT1-receptor antagonists was partly reduced (p < 0.01) by PD-123319 (the AT2-receptor antagonist). Glibenclamide had no effect on coronary vasodilation induced by sodium nitroprusside. These results indicate that in dogs in vivo, coronary vasodilation in response to AT 1-receptor antagonists inhibited markedly by glibenclamide and partly by PD-123319, suggesting that endogenous angiotensin II contributes to the maintenance of basal coronary vascular tone by acting at K+ATP channels through its receptors.
Tada
H
H
Research Institute of Angiocardiology and Cardiovascular Clinic, Kyushu University School of Medicine, Fukuoka, Japan.
Egashira
K
K
Yamamoto
M
M
Ueno
H
H
Takemoto
M
M
Shimokawa
H
H
Takeshita
A
A
D057911:Angiotensin Receptor Antagonists; D000818:Animals; D000959:Antihypertensive Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects*; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007093:Imidazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D026902:Potassium Channel Blockers; D011725:Pyridines / Q000494:pharmacology; D013777:Tetrazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D057911:Angiotensin Receptor Antagonists; D000959:Antihypertensive Agents; D004791:Enzyme Inhibitors; D007004:Hypoglycemic Agents; D007093:Imidazoles; D026902:Potassium Channel Blockers; D011725:Pyridines; D013777:Tetrazoles; C073402:PD 123319; C070967:L 158809; D005905:Glyburide; D019331:NG-Nitroarginine Methyl Ester