Independent induction and inhibition of ornithine decarboxylase and aryl hydrocarbon hydroxylase activities in rat epidermis.

Changes in the activities of ornithine decarboxylase (ODC) and aryl hydrocarbon hydroxylase (AHH) were investigated in rat epidermis after wounding the skin and application of 7,12-dimethylbenz(a)anthracene (DMBA), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and several enzyme inhibitors. Wounding of the skin by vigorous shaving led to a marked induction of ODC activity with a peak at 6 hr. Topical application of a single dose of tetradecanoylphorbol-13-acetate to wounded skin did not affect the activities of ODC and AHH. Application of single large dose (2.5 mg) of DMBA increased AHH activity 7-fold without affecting ODC activity. DL-alpha-difluoromethyl ornithine, a specific irreversible inhibitor of ODC, almost completely abolished ODC activity but did not inhibit DMBA- or TCDD-induced AHH activity. Several potential modifiers, including retinoic acid, indomethacin, 1,3-diamino-2-propranol, alpha-naphthoflavone, and SKF 525 A had unequal effects on ODC and AHH activities. These data indicate that ODC and AHH induction processes in the epidermis are independent biochemical events that are not causally related.