Effects of endurance training on activity and expression of AMP-activated protein kinase isoforms in rat muscles

The effects of endurance training on the response of muscle AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) to moderate treadmill exercise were examined. In red quadriceps, there was a large activation of alpha2-AMPK and inactivation of ACC in response to exercise. This response was greatly reduced after training, probably because of reduced metabolic stress. In white quadriceps, there were no effects of exercise on AMPK or ACC, but alpha2-activity was higher after training because of increased phosphorylation of Thr(172). In soleus, there were small increases in alpha2-activity during exercise that were not affected by training. The expression of all seven AMPK subunit isoforms was also examined. The beta2- and gamma2-isoforms were most highly expressed in white quadriceps, and gamma3 was expressed in red quadriceps and soleus. There was a threefold increase in expression of gamma3 after training in red quadriceps only. Our results suggest that gamma3 might have a special role in the adaptation to endurance exercise in muscles utilizing oxidative metabolism.