Opening of mitochondrial KATP channel occurs downstream of PKC-ε activation in the mechanism of preconditioning

We examined whether the mitochondrial ATP-sensitive K channel (K-ATP) is an effector downstream of protein kinase C-epsilon (PKC-epsilon) in the mechanism of preconditioning (PC) in isolated rabbit hearts. PC with two cycles of 5-min ischemia/5-min reperfusion before 30-min global ischemia reduced infarction from 50.3 +/- 6.8% of the left ventricle to 20.3 +/- 3.7%. PC significantly increased PKC-epsilon protein in the particulate fraction from 51 +/- 4% of the total to 60 +/- 4%, whereas no translocation was observed for PKC-delta and PKC-alpha. In mitochondria separated from the other particulate fractions, PC increased the PKC-epsilon level by 50%. Infusion of 5-hydroxydecanoate (5-HD), a mitochondrial K-ATP blocker, after PC abolished the cardioprotection of PC, whereas PKC-epsilon translocation by PC was not interfered with 5-HD. Diazoxide, a mitochondrial K-ATP opener, infused 10 min before ischemia limited infarct size to 5.2 +/- 1.4%, but this agent neither translocated PKC-epsilon by itself nor accelerated PKC-epsilon translocation after ischemia. Together with the results of earlier studies showing mitochondrial K-ATP opening by PKC, the present results suggest that mitochondrial K-ATP-mediated cardioprotection occurs subsequent to PKC-epsilon activation by PC.