Ischemic preconditioning depends on interaction between mitochondrial K-ATP channels and actin cytoskeleton

Both mitochondrial ATP-sensitive K+ (K-ATP) channels and the actin cytoskel eton have been proposed to be end-effectors in ischemic preconditioning (PC ). For evaluation of the participation of these proposed end effecters, rab bits underwent 30 min of regional ischemia and 3 h of reperfusion. PC by 5- min ischemia + l0-min reperfusion reduced infarct size by 60%. Diazoxide, a mitochondrial K-ATP-channel opener, administered before ischemia was prote ctive. Protection was lost when diazoxide was given after onset of ischemia . Anisomycin, a p38/JNK activator, reduced infarct size, but protection fro m both diazoxide and anisomycin was abolished by 5-hydroxydecanoate (5-HD) an inhibitor of mitochondrial KATP channels. Isolated adult rabbit cardiomy ocytes were subjected to simulated ischemia by centrifuging the cells into an oxygen-free pellet for 3 h. PC was induced by prior pelleting for 10 min followed by resuspension for 15 min. Osmotic fragility was assessed by add ing cells to hypotonic (85 mosmol) Trypan blue. PC delayed the progressive increase in fragility seen in non-PC cells. Incubation with diazoxide or pi nacidil was as protective as PC. Anisomycin reduced osmotic fragility, and this was reversed by 5-HD. Interestingly, protection by PC, diazoxide, and pinacidil could be abolished by disruption of the cytoskeleton by cytochala sin D. These data support a role for both mitochondrial KATP channels and c ytoskeletal actin in protection by PC.