Role of mitochondrial and sarcolemmal K_ATP channels in ischemic preconditioning of the canine heart

We tested whether mitochondrial or sarcolemmal ATP-sensitive K′ (K_ATP) channels play a key role in ischemic preconditioning (IP) in canine hearts. In open-chest beagle dogs, the left anterior descending artery was occluded four times for 5 min each with 5-min intervals of reperfusion (IP), occluded for 90 min, and reperfused for 6 h. IP as well as cromakalim and nicorandil (nonspecific K_ATP channel openers) markedly limited infarct size (6.3 ± 1.2, 8.9 ± 1.9, and 7.2 ± 1.6%, respectively) compared with the control group (40.9 ± 4.1%). A selective mitochondrial K_ATP channel blocker, 5-hydroxydecanoate, partially blunted the limitation of infarct size in the animals subjected to IP and those treated with cromakalim and nicorandil (21.6 ± 3.8, 25.1 ± 4.6, and 19.8 ± 5.2%, respectively). A nonspecific K_ATP channel blocker, glibenclamide, completely abolished the effect of IP (38.5 ± 6.2%). Intracoronary or intravenous administration of a mitochondria-selective K_ATP channel opener, diazoxide, at >100 μmol/l could only partially decrease infarct size (19.5 ± 4.3 and 20.1 ± 4.4%, respectively). In conclusion, mitochondrial and sarcolemmal K_ATP channels independently play an important role in the limitation of infarct size by IP in the canine heart.