Abstract
Effects of isoproterenol in vivo and in vitro were investigated in order to determine the correlation between release of liver potassium and glycogenolytic action induced by epinephrine. Results are as follows. Intravenous administration of isoproterenol in pentobarbital anesthetized dogs caused a transient rise of serum potassium followed by an after-fall like epinephrine. Hyperkalemic effect of isoproterenol, like cyclic AMP, was about 1/4 as potent as that of epinephrine in so far as these agents revealed almost equivalent responses on hyperglycemia and liver phosphorylase activation. Increase in liver cyclic AMP level induced by isoproterenol was similar to that of epinephrine. Hyperkalemic effect of epinephrine was inhibited by both α and β-adrenergic blocking agents, dihydroergotamine and dichloroisoproterenol, whereas that of isoproterenol was inhibited by only the β-blocking agent. Dog liver adenyl cyclase activity was lowered by potassium in vitro, while increase in the enzyme activity induced by isoproterenol was not altered by a simultaneous addition of potassium.
