To determine role of the ATP-sensitive potassium channel (KATP channel) in myocardial function during myocardial ischemia, we evaluated regional myocardial shortening and myocardial blood flow using a constant, low flow perfusion system in open-chest dogs. Coronary blood flow was decreased to halt the control level by constricting the perfusion line with a constant pressure throughout the experiment. Glibenclamide (G), a KATP channel blocker, and pinacidil (P), a KATP channel opener, was infused into the coronary perfusion line after the flow was reduced. When coronary flow was reduced, coronary perfusion pressure was decreased to 55% of the control value, segmental shortening (% SS) of the subendocarial myocardium from 18±2% to 13±2% (mean ± SEM)(P<0.05) and the subendocardial to subepicardial (endo/epi) blood flow ratio measured with colored micrsphers ranged from 1.17±0.04 to 0.82±0.05(p<0.05). The infusion of G caused further reduction of % SS to 3±1% (P<0.001) without significant change in the endo/epi blood flow ratio. Additional infusion of P improved % SS to 11±2%, which did not significanlty differ from the pre-G value. The fingings strongly strongly suggest that KATP channels participate in maintaining myocardial function during ischemia.
ATP-sensitive potassium channel
regional myocardial function