Role of K+ATP channels in coronary vasodilation during exercise.

BACKGROUNDThe mechanism of metabolic regulation of coronary vascular tone is still unclear. Therefore, we examined the role of vascular smooth muscle K+ATP channels in regulating coronary blood flow under resting conditions, during increments in myocardial metabolic demand produced by treadmill exercise, and in response to a brief ischemic stimulus.METHODS AND RESULTSTen chronically instrumented dogs were studied at rest and during a four-stage exercise protocol under control conditions and during intracoronary infusion of the K+ATP channel blocker glibenclamide at rates of 10 and 50 micrograms.kg-1 x min-1. Glibenclamide (50 micrograms.kg-1 x min-1) decreased coronary blood flow at rest from 51 +/- 4 to 42 +/- 6 mL/min (P < .05), decreased myocardial oxygen consumption from 5.70 +/- 0.31 to 4.11 +/- 0.56 mL O2/min (P < .05), and decreased systolic wall thickening from 21 +/- 3% to 12 +/- 3% (P < .05). The depression of systolic wall thickening produced by glibenclamide was reversed when coronary blood fl...