Steroidogenic assessment using ovary culture in cycling rats: effects of bis(2-diethylhexyl)phthalate on ovarian steroid production.

In vitro ovary culture in rats was used to characterize ovarian steroidogenesis and to evaluate changes produced by in vivo exposure to bis(2-diethylhexyl)phthalate (DEHP). Steroid profiles [progesterone (P4), estradiol (E2), and testosterone (T)] from cultures of minced ovary were obtained in untreated immature and mature rats, and from mature rats treated with DEHP. A 1-h incubation without human chorionic gonadotropin (hCG) was used to produce an initial steroidogenic profile. Three 1-h incubations with hCG were used to produce a stimulated steroid profile. A combination of initial and stimulated ovarian steroid profiles was shown to correctly identify the stage of the cycle in all untreated rats, using multivariate statistical analysis. Separately, initial or stimulated ovarian steroid profiles correctly identified the stage of the cycle in more than 90% of the rats. The statistical analysis using a combination of variables (multivariate) indicated that DEHP-treated rats were significantly different (P < 0.001) from sham-treated rats. In fact, the alteration caused by DEHP in the in vitro ovarian steroidogenic profile was most apparent in rats during diestrus and estrus. In DEHP-treated rats in diestrus, ovarian steroidogenesis appeared to shift to the production of more T and more E2 than in untreated rats in diestrus. The change seen in steroid profiles in DEHP-treated rats in estrus is to decreased E2 production. The steroid profile from ovary culture in conjunction with vaginal cytology was very useful in correctly identifying in vivo DEHP-treated rats, and will be a useful in vitro technique in the evaluation of ovarian toxicants in cycling females.