HYPERPLASIA OF SYRIAN-HAMSTER EPIDERMIS INDUCED BY SINGLE BUT NOT MULTIPLE TREATMENTS WITH 12-O-TETRADECANOYLPHORBOL-13-ACETATE

Abstract

Treatment of initiated hamster skin with 12-O-tetradecanoylphorbol-13-acetate [TPA] does not promote the formation of papillomas and carcinomas as it does in the classic 2-stage epidermal carcinogenesis model in many strains of mice. The basis of the species specificity to TPA was studied. Although hamster and mouse epidermis respond to a single exposure of TPA with a comparable degree of hyperplasia, they differ in their response to multiple treatments. In contrast to the reported potentiation of hyperplasia of mouse skin following 2 or more treatments with TPA, hamster skin is capable of adapting to multiple exposures to the promoter. Weekly TPA treatments of hamster skin result in hyperplasia of 4-6 nucleated cell layers after the 1st treatment, reduced hyperplasia after the 2nd treatment and no hyperplasia after 4 wk of treatment. Decreasing the time interval between treatments accelerates the adaptation process. This adaptation phenomenon should be useful in studying the mechanism of TPA action by examining TPA effects in adapted and nonadapted tissues from the same species.