STIMULATION OF RNA-SYNTHESIS IN RAT PAROTID LOBULES BY PHORBOL-MYRISTATE ACETATE

Incubation of parotid lobules with phorbol 12-myristate 13-acetate (PM A) transiently stimulated the incorporation of [H-3]-uridine into RNA. At 100 nM PMA, the rate of RNA synthesis during the first hour was 30 % above control rates. The Ca2+ ionophore A23187 had no effect on eith er basal or PMA-stimulated RNA synthesis. Stimulation by 100 nM PMA wa s reversed by the protein kinase C inhibitor staurosporin (10 nM). Whe n PMA was added together with isoproterenol or okadaic acid, both of w hich are potent activators of RNA synthesis, the increase in RNA synth esis was additive rather than synergistic. The results suggest that in the rat parotid gland, protein kinase C induces the rapid transcripti on of certain cellular genes by a mechanism that is independent of the beta-adrenergic receptor-activated pathway.