Dissociation of Increases in Levels of 3′:5′-cyclic AMP and 3′:5′-cyclic GMP from Induction of Ornithine Decarboxylase by the Tumor Promoter 12-O-tetradecanoyl Phorbol- 13-acetate in Mouse Epidermis in vivo

A single application of 17 nmol of 12-O-tetradecanoyl phorbol-13-acetate (TPA) to mouse skin caused a marked (200-to 400-fold) induction of ornithine decarboxylase (EC 4.1.1.17, L-ornithine carboxy-lyase) activity in mouse epidermal and epidermal-dermal preparations. No change in the basal level of 3′:5′-cyclic AMP occurred in epidermal-dermal preparations within 30 min of TPA application. Intraperitoneal injection of the β -agonist isoproterenol resulted in a dose-dependent accumulation of 3′:5′-cyclic AMP 10 min after injection, but caused no induction of ornithine decarboxylase. When isoproterenol was injected 10 min prior to an application of either 1.7 or 17 nmol of TPA, the magnitude of the ornithine decarboxylase induction was the same as induction with TPA alone. Topical application of 17 nmol of TPA caused no increase in the level of 3′:5′-cyclic GMP present in the mouse epidermaldermal preparations 2-20 min after application. Intraperitoneal injection of 1.75 μ mol of dibutyryl 3′:5′-cyclic GMP caused a 6-fold increase in the level of cyclic GMP and/or butyryl derivatives of cyclic GMP in epidermal-dermal preparations within 5 min of injection, and the level remained elevated for at least 20-30 min. This dose of dibutyryl 3′:5′-cyclic GMP was incapable of inducing ornithine decarboxylase. Injection of dibutyryl 3′:5′-cyclic GMP 5 min before application of 1.7 nmol of TPA or 30 min before application of 17 nmol of TPA did not alter the magnitude of the ornithine decarboxylase induction produced by TPA alone. These results suggest that early increases in the total intracellular levels of either 3′:5′-cyclic AMP or 3′:5′-cyclic GMP are not part of the mechanism by which TPA induces ornithine decarboxylase in the epidermis.