Cyclic AMP Metabolism In Cardiac Tissue Of Spontaneously Hypertensive Rats: Adenyl Cyclase Activity

Abstract

Cyclic AMP was discovered in 1956 by Rall, Berthet, and Sutherland, who had been studying the stimulation of glycogenolysis by glucagon and epinephrine. A heat-stable factor was found to mediate the action of these hormones on the activation of liver phosphorylase (Figure 1). The factor increased the rate at which phosphorylase b (inactive) was converted to phosphorylase a (active) by stimulation of dephosphophosphorylase kinase (37). Later identified as adenosine 3',5'-monophosphate or cyclic AMP (23, 24), this factor was also found to inhibit the formation of glycogen by its action on a synthetase kinase (37). Thus it was shown that in the liver, glucagon and epinephrine stimulate glycogenolysis via cyclic AMP; the nucleotide simultaneously increases the rate of glycogen breakdown and slows the rate of glycogen formation.