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This Article Full Text Full Text (PDF) All Versions of this Article: 68/1/244    most recent biolreprod.102.007161v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Morán, F.M. Articles by Lasley, B.L. Search for Related Content PubMed PubMed Citation Articles by Morán, F.M. Articles by Lasley, B.L. Agricola Articles by Morán, F.M. Articles by Lasley, B.L.

Exogenous Steroid Substrate Modifies the Effect of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin on Estradiol Production of Human Luteinized Granulosa Cells In Vitro¹

^a Population Health and Reproduction, ^b Center for Health and the Environment, ^c California National Primate Research Center, University of California, Davis, Davis, California 95616

The in vitro effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on steroid metabolism in human luteinized granulosa cells (hLGC) have been summarized as a decreased estradiol (E₂) production without altering either E₂ metabolism or cytochrome P450 aromatase activity. In the present study, hLGC were used to analyze the fate of different substrates for cytochrome P450 17-hydroxylase/17,20-lyase (P450_c17) in the presence or absence of TCDD. Human LGCs were plated directly on plastic culture dishes in medium supplemented with 2 IU/ml of hCG. TCDD (10 nM) or its solvent was added directly to the cells at the time of medium change, every 48 h for 8 days. The objective of the experiment was to test the hypothesis that exogenous steroid, substrate for P450_c17, would reduce the TCDD effects on E₂ synthesis. With dehydroepiandrosterone (DHEA) (a P450_c17 product), a dose-related increase in E₂ production was observed and the effect of TCDD on lowering E₂ production disappeared. In contrast, with increasing doses, up to 10 µM, of pregnenolone (P₅), no change in E₂ production was observed. However, 17-hydroxypregnenolone (17P₅) at 10 µM produced a modest but significant increase in the E₂ production. Treatments with P₅ and 17P₅ did not alter the effect of TCDD on E₂ production. Radiolabeled substrate utilization by hLGC suggests that the principal metabolic pathway for 5 substrates is the conversion to a 4 product probably by a very active 3ß-hydroxysteroid dehydrogenase. We conclude that estrogen production by hLGC is limited at the level of lyase activity. Thus, these data suggest that the most likely target for the TCDD-induced inhibition of estrogen synthesis by hLGC is the 17,20-lyase activity of the P450_c17 enzyme complex.

¹ Supported by NIEHS ESO06198.

² Correspondence: Bill L. Lasley, Center for Health and the Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616-8615. FAX: 530 752 5300; bllasley{at}ucdavis.edu