| Abstract: | Previous studies have demonstrated that catecholamine responsiveness in a variety of cells can be altered by inhibitors of RNA and protein synthesis. The neuroblastoma-glioma hybrid, NG108-CC15, which lacks catecholamine-stimulated accumulation of cyclic AMP, was investigated to determine if the responsiveness to prostaglandin E1 (PGE1) could be modified by inhibitors of protein synthesis. Cycloheximide in a time-dependent manner potentiated the ability of prostaglandin E1 to stimulate accumulation of intracellular cyclic AMP. However, the alpha-adrenergic inhibition of the prostaglandin response was not affected by cycloheximide. Withdrawal of norepinephrine following a long-term incubation resulted in a potentiation of subsequent PGE1-stimulated cyclic AMP accumulation. Cycloheximide enhanced this norepinephrine withdrawal effect. Our previous studies have shown that cholera toxin induces refractoriness to beta-adrenergic agonists in C6-2B rat astrocytoma cells and that cycloheximide blocked this action of cholera toxin. In an analogous manner cholera toxin caused refractoriness to subsequent prostaglandin-stimulated cyclic AMP production in NG108-CC15 cells, and cycloheximide reduced cholera toxin-induced prostaglandin refractoriness. Thus cycloheximide potentiates the prostaglandin stimulatory effect, has no effect on the ability of alpha-agonists to inhibit the prostaglandin response, increases the stimulatory effect of PGE1 after norepinephrine withdrawal, and reduces cholera toxin-induced PGE1 refractoriness. these observations suggest that PGE1-stimulated cyclic AMP accumulation in NG108-CC15 cells contains components which are regulated by de novo protein synthesis. |
