title: Mono-(2-ethylhexyl) phthalate suppresses estradiol production independent of FSH-cAMP stimulation in rat granulosa cells.
abstract: Di-(2-ethylhexyl) phthalate (DEHP) exposure suppressed preovulatory granulosa cell estradiol production in adult cycling rats. The active metabolite of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), suppressed follicle-stimulating hormone (FSH)-stimulated cAMP and progesterone production in cultured rat granulosa cells. To examine how DEHP altered granulosa cell estradiol production, the effects of MEHP were studied in cultures of rat granulosa cells. Granulosa cells were obtained from DES-implanted 25-day-old female Fisher 344 rats and exposed in culture to various concentrations of MEHP (0 to 400 microM) in DMSO. Granulosa cells were stimulated with FSH, 8-bromo cyclic adenosine monophosphate (8br-cAMP), a stable cAMP analog, and various concentrations of testosterone. Estradiol production was measured by standard radioimmunoassays and normalized to cell protein. MEHP suppressed estradiol in a concentration-dependent manner whether granulosa cells were stimulated by FSH or 8-br cAMP. Therefore, MEHP suppressed estradiol independent of its suppression of the FSH-cAMP pathway and, thus, suppressed aromatase conversion of testosterone to estradiol. MEHP (100 microns) decreased the maximum velocity of aromatase in cells supplied with increasing concentrations of testosterone. However, MEHP did not alter the velocity or affinity of microsomal aromatase isolated from adult virgin Sprague-Dawley rat ovaries. Therefore, MEHP altered the absolute amount or availability of aromatase in granulosa cells. Decreased aromatase in granulosa cells would explain decreased estradiol concentrations from DEHP exposure in vivo.
authors.affiliation: Department of Microbiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
authors.forename: B J
authors.initials: BJ
authors.lastname: Davis
authors.forename: R
authors.initials: R
authors.lastname: Weaver
authors.forename: L J
authors.initials: LJ
authors.lastname: Gaines
authors.forename: J J
authors.initials: JJ
authors.lastname: Heindel
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001141:Aromatase / Q000378:metabolism; D002452:Cell Count / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004051:Diethylhexyl Phthalate / Q000031:analogs & derivatives* / Q000633:toxicity; D004958:Estradiol / Q000096:biosynthesis*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism* / Q000494:pharmacology; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011916:Rats, Inbred F344; D013739:Testosterone / Q000494:pharmacology
chemical_list: D003609:Dactinomycin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D005640:Follicle Stimulating Hormone; D003513:Cycloheximide; D004051:Diethylhexyl Phthalate; D000242:Cyclic AMP; D001141:Aromatase; C016599:mono-(2-ethylhexyl)phthalate