Increased mouse epidermal ornithine decarboxylase activity by the tumour promoter 12-O-tetradecanoylphorbol 13-acetate involves increased amounts of both enzyme protein and messenger RNA.

Evidence was sought that the tumour promoter 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced mouse epidermal ornithine decarboxylase (ODC, EC 4.1.1.17) activity involves both increased ODC mRNA and ODC protein. Application of 10 nmol of TPA to mouse skin led to a dramatic increase in soluble epidermal ODC activity which paralleled an increase in amount of enzymically active ODC protein as determined by gel electrophoresis of immunoprecipitated difluoromethyl[3H]ornithine-bound ODC. Application of TPA to mouse skin also resulted in an increase in ODC mRNA measured by dot-blot analysis using a radiolabelled cDNA probe. ODC mRNA induction preceded the increase in ODC activity by TPA. TPA-increased ODC mRNA displayed a single major band of 2.1 kilobases in size identified by the Northern blotting procedure.