The intracellular localization of topically applied antiand syn diastereomers of racemic benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) was investigated in SENCAR mouse epidermis using conventional electron microscopic (EM) autoradiography. The shaved backs of adult mice were treated in vivo with the active skin tumor initiator anti[3H]BPDE or with its stereoisomersyn [3H]BPDE, which is inactive as an initiator. After 3, 12 and 24 h of exposure, thin sections of the treated skin were prepared for high resolution autoradiography to determine the intracellular distributions of radioactivity bound within the epidermis. For each treatment and exposure time, the interfollicular area of epidermis examined by EM encompassed 350-700 keratinocytes, and extended from the basal lamina to the innermost keratinizing layer at a magnification that permitted basal and suprabasal cell populations to be distinguished in situfollowing autoradiography. Statistical analysis of the distributions of silver grains localized over keratinocytes at 3-, 12- and 24-h timepoints revealed that 27.2% of the carcinogenic anti [3H]BPDE grains occurred over epidermal nuclei, which was significantly more (P < 0.001) than 20.0% of the non-carcinogenic syn [3H]BPDE grains associated with nuclei at all timepoints examined. In the basal cell population at the 3-h time point 33% of both racemic diastereomers were found within nuclei; at 12 and 24 h of exposure the nuclear association of anti [3H]BPDE grains increased (P < 0.01) to 39% and 47% respectively, while the nuclear-associated syn [3H]BPDE grains remained at 29% and 33%. The localization of [3H]BPDE observed in our experiments suggests that the epidermal cell nucleus may be an important intracellular target for antiBPDE.
ASJC Scopus subject areas
- Cancer Research