EFFECT OF ENDURANCE PHYSICAL-TRAINING ON RAT-LIVER ADENYLYL-CYCLASE SYSTEM

The adaptive response to endurance exercise of the catecholamine- and glucagon-sensitive adenylyl cyclase system was studied in rat liver pl asma membranes. Endurance exercise enhanced adenylyl cyclase system ac tivation by cellular agonists (glucagon, isoproterenol), by stimulator s of the enzyme catalytic subunit (forskolin, Mn2+), and by G(s)-prote in activators (GppNHp, fluoride). In addition, endurance exercise incr eased the levels of G(s alpha), G(i alpha), and G(beta) subunits. Thes e results show that the adenylyl cyclase system becomes sensitized in response to physical training.