Reproduction Abstracts

Introduction: Previous reports in different species have shown that various endocrine disrupting chemicals (EDCs) can modulate ovarian steroidogenesis with the majority of studies focussing on granulosa cells. To test the hypothesis that exposure to EDCs might also perturb thecal steroidogenesis we conducted in vitro dose–response experiments to evaluate the direct effects of selected EDCs on androstenedione and progesterone production by cultured bovine theca cells.

Methods: Theca interna cells from 4 to 8 mm follicles were cultured for 6 days in serum-free medium. Cells were treated for 4 days under basal and LH-stimulated conditions with/without selected EDCs including bisphenol A (10 pM–10 μM) DDT (50 pM–50 μM), methoxyclor (50 pM–50 μM) and ethinylestradiol (10 pM–10 μM). Androstenedione and progesterone concentrations in media were determined by ELISA; viable cell number was determined by neutral red uptake assay. Results are based on four independent batches of cells.

Results and discussion: Bisphenol A at 1–10 μM, DDT at 5–50 μM, and methoxyclor at 5–50 μM suppressed basal and LH-induced secretion of both androstenedione and progesterone (P<0.001) without affecting viable cell number. In contrast, ethinylestradiol at 1–10 μM enhanced basal and LH-induced androstenedione production (P<0.001) but suppressed LH-induced progesterone production (P<0.05). These results indicate that whilst lower (sub-micromolar) concentrations of these EDCs are without effect, at higher concentrations they can directly perturb steroidogenesis by ovarian theca cells. Studies are in progress to address the mechanism(s) through which thecal steroidogenesis is affected (e.g. altered expression and/or activity of steroidogenic pathway components). Whether environmentally-relevant exposure levels of these EDCs would generate intraovarian concentrations sufficient to adversely affect steroidogenesis remains to be established.