Comparative studies on the effects of isoproterenol and glucagon on 3′,5′-cyclic monophosphate metabolism in embryonic and newborn chick liver

Abstract

1. 1. The endogenous level of adenosine 3′,5′-cyclic monophosphate (cyclic-AMP) in developing chick liver was determined and found to be the highest at the earliest stage studied (6-day embryo) and to fall progressively to reach a lower plateau after about two weeks incubation. 2. 2. Isoproterenol or glucagon produce elevations in the cyclic-AMP content of 7–9-day embryonic liver in vitro but have little effect on the cyclic-AMP content of newborn chick liver slices in vitro. 3. 3. Kinetic plots of the phosphodiesterase activity in whole homogenates of embryonic or newborn chick liver are biphasic indicating the presence of 2 phosphodiestcrases. The activities of these 2 enzymes do not change markedly during development. 4. 4. The basal and fluoride stimulated adenylate cyclase activities of preparations of chick liver are lower than similar preparations of 7–9-day embryonic liver. Both types of preparations are stimulated by isoproterenol. 5. 5. The relationships between cyclic-AMP and the control of glycogen metabolism in the developing chick are discussed.