Cyclic AMP-dependent regulation of activities of synthetase and phosphodiesterase of 2',5'-oligoadenylate in NIH 3T3 cells.

Treatment of NIH 3T3 cells with adenylate cyclase activator adrenaline (10(-6) M) or cAMP phosphodiesterase inhibitor theophylline (10(-3) M) was shown to lead to intracellular cAMP elevation followed by a 2.0-to 2.5-fold increase in the 2',5'-oligoadenylate synthetase activity. This process was blocked by actinomycin D. The rise in the intracellular cAMP level was also followed by a 3-4-fold decrease in the activity of 2'-phosphodiesterase. Propranolol prevented this inhibition but actinomycin D produced only a negligible effect on the process. Incubation of the cell homogenate with purified catalytic subunit of cAMP-dependent protein kinase and ATP also resulted in a decrease of 2'-phosphodiesterase activity. These results indicate that cAMP is involved in the regulation of enzymes of the 2',5'-oligoadenylate system. The possibility that certain biological functions of cAMP are implemented via 2',5'-oligoadenylate-dependent processes is discussed.