Activation of Akt during simulated ischemia/reperfusion in cardiac myocytes

In the present study we have investigated whether Akt was activated during simulated ischemia (SI) and simulated ischemia/reperfusion (SI/R) in neonat al rat cardiomyocytes. Akt was phosphorylated on both S473 and T308 residue s after 10 min of simulated SI/R and remained elevated for 60 min before re turning to basal levels after 2 h. No phosphorylation was observed during S I alone. SI/R-stimulated Akt activation was inhibited by the phosphatidylin ositol S-kinase (PI3-K) inhibitor wortmannin, the tyrosine kinase inhibitor genistein and the Src tyrosine kinase inhibitor PP2, indicating a requirem ent for tyrosine kinase activity in Akt activation. Furthermore, SB203580, a p38 MAPK inhibitor, partially inhibited Akt activation. SI/R also induced the phosphorylation of PHAS-I, a downstream Akt target, in a wortmannin-de pendent manner. These results demonstrate for the first time that SI/R stim ulates Akt activation via PI3-K-and Src tyrosine kinase-dependent pathways, whereas p38 MAPK appears to be involved in maintaining Akt activation. (C) 2000 Academic Press.