Coronary vascular ATP-sensitive potassium channels are activated to a greater extent in spontaneously hypertensive rats than in Wistar-Kyoto rats.
OBJECTIVE
To determine whether opening of coronary vascular adenosine 5'-triphosphate (ATP)-sensitive potassium (KATP) channels is involved in the maintenance of resting coronary flow in hypertrophied hearts.


METHODS
We examined the effects of glibenclamide, a selective inhibitor of KATP channels, on basal coronary vascular tone in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Using a Langendorff system, the hearts from WKY rats and SHRs were isolated and perfused with oxygenated Krebs-Henseleit solution at a constant perfusion pressure of 60 and 100 mmHg respectively.


RESULTS
Basal coronary flow and myocardial oxygen consumption (MV02) were similar in SHRs and WKY rats. The percentage decreases in coronary flow with glibenclamide at graded doses were greater (P < 0.01) in SHRs than in WKY rats (n = 8), whereas the percentage decreases in MV02 with glibenclamide were similar in the two groups. The decreases in coronary flow caused by U46619 (a thromboxane A2-mimetic agent) were similar in SHRs and WKY rats (n = 4). The increase in coronary flow caused by pinacidil (a KATP opener) was greater in SHRs than in WKY rats; glibenclamide prevented the pinacidil-induced increase in coronary flow in both SHRs and WKY rats. There was a significant positive correlation between the glibenclamide-induced decrease in coronary flow and the degree of left ventricular hypertrophy (r = 0.54, P < 0.05).


CONCLUSIONS
Our results suggest that the basal opening state of coronary vascular KATP channels is activated to a greater extent in SHRs than WKY rats, which may contribute to the maintenance of basal myocardial perfusion in hypertrophied hearts.
Numaguchi
K
K
Research Institute of Angiocardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Egashira
K
K
Sakata
M
M
Shimokawa
H
H
Takeshita
A
A
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D005905:Glyburide / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D017379:Hypertrophy, Left Ventricular / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009206:Myocardium / Q000378:metabolism; D009929:Organ Size; D010101:Oxygen Consumption; D020110:Pinacidil; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D006146:Guanidines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011450:Prostaglandin Endoperoxides, Synthetic; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D020110:Pinacidil; D000255:Adenosine Triphosphate; D005905:Glyburide