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.