Rat hearts were perfused for 1 h with 5 mMglucose with or without palmitate or oleate at concentrations characteristic of the fasting state. The inclusion of fatty acids resulted in increased activities of the a-1 or thea-2 isoforms of AMP-activated protein kinase (AMPK), increased phosphoryla-tion of acetyl-CoA carboxylase and a decrease in the tissue content of malonyl-CoA. Activation of AMPK was not accompanied by any changes in the tissue contents of ATP, ADP, AMP, phosphocreatine or creatine. .
