MODULATION OF 12-O-TETRADECANOYLPHORBOL-13-ACETATE-INDUCED EPIDERMAL ORNITHINE DECARBOXYLASE ACTIVITY BY CALCIUM AND VERAPAMIL IN MOUSE

Calcium has been suggested to be an intracellular second messenger for ornithine decarboxylase (ODC) induction caused by 12-O-tetradecanoylp horbol-13-acetate (TPA). In the present study, the effects of dietary calcium supplement and calcium and verapamil injections on TPA-induced ODC activity in skin was investigated in CD-1 and SENCAR mouse. Dieta ry calcium supplement did not influence ODC induction caused by TPA. H owever, calcium injections enhanced the TPA-induced ODC activity in CD -1 and SENCAR mouse skin. Verapamil injections resulted in a significa nt decrease in TPA-induced ODC activity in CD-1 and SENCAR mice. These results suggest that calcium and calcium antagonists may play a role in tumor promotion caused by TPA. (C) 1994 Academic Press, Inc.