Abstract
Enzyme histochemical studies of normal and burned mouse skin as well as those treated with methylcholanthrene or 2,4-dinitro-1-chlorobenzene revealed that the irritant (or stimulus) carcinogenic or noncarcinogenic, initially results in a more distinct polarization2 of the localization of oxidative enzymes including glucose 6-phosphate dehydrogenase (predominant in the upper layers of the hypertrophic epidermis) and DPN-dependent dehydrogenases, succinic dehydrogenase and cytochrome oxidase in the lower layers. Subsequently, only the carcinogen disrupted the polarization pattern. Methylcholanthrene-induced squamous cell carcinomas were classified from a histochemical standpoint according to the following three types: (1) those well differentiated and having a distinctly polarized pattern of oxidative enzymes; (2) those showing disruption of the polarization pattern and marked activity of oxidative enzymes; and (3) those that were undifferentiated and characterized by absence of a polarized pattern and weak activity of oxidative enzymes. Type 1 showed an enzyme distribution pattern resembling that of the inflammatory hypertrophic epidermis; type 2 was similar in enzymatic pattern to the advancing proximal portion of the regenerating epidermis; and type 3 was similar enzyme-histochemically to the undifferentiated epithelium of the early embryo skin. Thus, a great variation in the distribution pattern of enzyme activities appears during the carcinogenesis process.