The metabolism of 7,12-dimethylbenz(a)anthracene (DMBA) by primary cultures of human ovarian cells has been studied to identify the cell type(s) responsible for biotransformation of this carcinogen. The rate of DMBA metabolism was maximal in granulosa cells prestimulated in vivo with antiestrogen, hMG (human menopausal gonadotropin) and hCG (human chorionic gonadotropin), i.e., treatments required for maximal oocyte maturation and, thus, granulosa cell proliferation. In cells from unstimulated ovaries, the metabolism was maximal in granulosa-lutein cells isolated from corpus luteum. 2. Steroid (progesterone and estradiol) levels were determined in the spent culture media or in media in parallel with DMBA metabolism to find out whether elevated steroid levels in vivo are required for the rapid metabolism of DMBA. In granulosa cell cultures from stimulated cycles, the concentrations of both progesterone and estradiol were at least 2 or 3 times higher, respectively, than in any of the other cell types tested. In cell cultures derived from unstimulated ovaries, the progesterone and estradiol concentrations were highest in granulosa-lutein cell cultures. 3. Incubations of granulosa cells with DMBA in the absence or presence of gonadotropins, testosterone or anti--hCG were performed to investigate possible hormonal requirements for the cytochrome P-450 system(s) which metabolize DMBA. No change in the rate of metabolism was obtained with follicle stimulating hormone (FSH), luteinizing hormone (LH), hCG or testosterone. However, anti-hCG increased this activity about 70%, indicating a negative modulatory role of hCG on DMBA mono-oxygenase activity in human granulosa cells. 4. DMBA mono-oxygenase activity in cell cultures was inhibited about 95% by alpha-naphthoflavone (ANF), an inhibitor of certain cytochrome P-450-catalysed activities. Benzo(a)pyrene (BP) was metabolized at the same rate as DMBA in granulosa cell cultures.
