Role of protein kinase C-alpha in activation of ecto-5'-nucleotidase in the preconditioned canine myocardium

We have reported that activation of protein kinase C (PRC) increases ecto-5'-nucleotidase activity, which may contribute to the infarct size-limiting effect of ischemic preconditioning. Since we have reported that Ca2+- and phospholipid-sensitive PKC is activated due to ischemic preconditioning, we further tested 1) whether PKC-alpha or -beta is translocated to the cellular membrane of the preconditioned canine myocardium, and 2) whether activation of PFC contributes to the increase in ecto-5'-nucleotidase activity via phosphorylation-dependent mechanisms. Four times of 5 minutes coronary occlusion separated by 5 minutes of reperfusion (ischemic preconditioning) translocated PKC-alpha to the cellular membrane in the canine hearts, although PKC-beta, -delta, -epsilon, and -zeta were not translocated, The activity of Ca2+- and phospholipid-sensitive PHC increased, which was attenuated by the removal of either Ca2+ or phosphatidylserine, Ecto-5'-nucleotidase was also activated in the preconditioned myocardium compared with control. Inhibition of PKC due to GF109203X blunted the activation of myocardial ecto-5'-nucleotidase. Okadaic acid (an inhibitor of phosphatase) enhanced the increases in ecto-5'-nucleotidase activity due to preconditioning, and this enhancement was blunted by GF109203X, We conclude that ischemic preconditioning activates PKC-alpha, and thus ecto-5'nucleotidase. (C) 1997 Academic Press.