EFFECT OF BLOCKADE OF THE ATP-SENSITIVE POTASSIUM CHANNEL ON METABOLIC CORONARY VASODILATION IN THE DOG

The hypothesis that the ATP-sensitive potassium channel provides the l ink between change in coronary blood flow and myocardial oxygen demand was tested in 9 dogs instrumented to measure coronary flow and region al wall thickening in the basal state and at a high level of myocardia l oxygen consumption produced by systemic infusion of phenylephrine an d simultaneous atrial pacing at an elevated heart rate. Measurements w ere recorded before and after blockade of ATP-sensitive potassium chan nels with intracoronary glibenclamide (2 mumol/min). While glibenclami de reduced the absolute level of coronary flow in the basal state, the increase in flow due to increased metabolic demand was unchanged comp ared with control. Thus, activity of the ATP-sensitive potassium chann el determines the set point from which adjustments of coronary flow in response to metabolic stimuli occur, but does not provide a link betw een changes in oxygen demand and changes in coronary flow.