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Metabolism of the carcinogenic hydrocarbon benzo(a)pyrene in human fibroblast and epithelial cells

Metabolism of the carcinogenic hydrocarbon benzo(a)pyrene (BP) to water and alkali‐soluble products was measured in cultured fibroblast and epithelial cells from human embryos. The alkali‐soluble products represented only a small fraction of BP metabolism. Fibroblasts from different organs from the same embryo metabolized similar amounts of BP, while those derived from different embryos can metabolize different amounts. The fibroblasts were divided into three groups which metabolized an average of 350, 850 and 3,400 μμmoles of water soluble products/106cells/3 days. No significant differences were found in relationship to the age of the embryos from 2.5 to 5 months. Fibroblasts from the endometrium of adult women metabolized less than embryonic fibroblasts. Cultures which contained more than 20% epithelial cells metabolized 3–25 times more BP than fibroblast cultures from the same embryo. Epithelial cells from different embryos also varied in the degree of BP metabolism and low epithelial activity was not necessarily associated with low fibroblast activity in the same embryo. It is suggested that there is a genetic heterogeneity in BP metabolism in fibroblast and epithelial cells, and that the higher activity of epithelial cells might be related to the higher incidence of carcinomas rather than sarcomas in humans.