Endurance training, not acute exercise, differentially alters beta -receptors and cyclase in skeletal fiber types

beta -Adrenergic receptor binding characteristics and adenylate cyclase activity were examined in rat skeletal muscle membranes to determine if acute exercise or endurance training altered beta -receptors or adenylate cyclase activity in different muscle fiber types. Binding characteristics and adenylate cyclase activity were examined in type IIA (red fast-twitch, red vastus (RV)), type IIB (white fast-twitch, white vastus (WV)), and type I (red slow-twitch, soleus (S)) muscles. The data support and extend previous observations to show greater effects of endurance training in types I and IIA fibers with respect to alterations in beta -receptor density and alterations in adenylate cyclase activity in each fiber type. Acute exercise did not alter these parameters either in trained or untrained rats.