Cyclic AMP phosphodiesterase in cloned astrocytoma cells: Norepinephrine induces a specific enzyme form

Abstract

The soluble supernatant fraction of homogenates of cloned rat astrocytoma cells (line C-2A) was subjected to polyacrylamide gel electrophoresis. Two peaks of adenosine 3′,5′-monophosphate phosphodiesterase activity were found, corresponding to peaks I and IV of a similarly prepared homogenate of rat brain. Incubating cells with norepinephrine (0.3 millimolar) caused about a three-fold increase in the activity of peak IV but no change in peak I. This increase was completely inhibited by prior incubation with propranolol (0.1 millimolar), a beta-adrenergic blocking agent, or with cyclohexamine (40 micromolar), a protein synthesis inhibitor. Induction of a specific phosphodiesterase form by norepinephrine suggests another feedback control mechanism whereby an organism can prevent the effects of excessive sympathetic activity.