Insulin antagonizes AMP-activated protein kinase activation by ischemia oranoxia in rat hearts, without affecting total adenine nucleotides

AMP-activated protein kinase (AMPK) is known to be activated by phosphoryla tion on Thr172 in response to an increased AMP/ATP ratio. We report here th at such an activation indeed occurred in anaerobic rat hearts and that it w as antagonized (40-50%) when the hearts were pre-treated with 100 nM insuli n. The effect of insulin (1) was blocked by wortmannin, an inhibitor of pho sphatidylinositol-3-kinase; (2) only occurred when insulin was added before anoxia, suggesting a hierarchical control; (3) resulted in a decreased pho sphorylation state of Thr172 in AMPK and (4) was unrelated to changes in th e AMP/ATP ratio. This is the first demonstration that AMPK activity could b e changed without a detectable change in the AMP/ATP ratio of the cardiac c ell. (C) 2001 Federation of European Biochemical Societies. Published by El sevier Science B.V. All rights reserved.