Regulation of Steroidogenesis in Cultured Porcine Theca Cells by Growth Factors

Abstract

Growth factors [insulin-like growth factors (IGF-I, IGF-II), transforming growth factor-β (TGFβ), epidermal growth factors (EGF)], found in the ovary and known to alter granulosal function, were assessed for their ability to modulate porcine thecal steroidogenesis. Theca cells from large porcine follicles (8–10 mm) were plated (5 × 10⁵ cells/ml · well) in serum-free M199, treated with increasing doses of growth factors: IGF-I (0.1–50 ng/ml), IGF-II (0.5–200 ng/ml), EGF (0.021–100 ng/ml), TGFβ (0.001–40 ng/ml), or insulin (0.01–50 μg/ml), with or without human CG [(hCG); 20 ng/ml], and incubated for 72 h. Levels of steroids in media were determined by RIA. Insulin increased (P < 0.05) basal and gonadotropin-induced secretion of androstenedione, progesterone, estradiol, and testosterone. IGF-I increased (P < 0.05) the basal and hCG-induced secretion of progesterone and androstenedione at the highest doses, but did not affect basal secretion of estradiol or testosterone. IGF-II, at the highest doses, increased (P < 0.05) thecal steroidogenesis, but only after administration of hCG. In contrast, TGFβ increased (P < 0.05) basal and gonadotrophininduced secretion of estradiol but inhibited thecal secretion of progesterone, androstenedione, and testosterone. EGF did not alter thecal secretion of progesterone, androstenedione, or testosterone but significantly (P < 0.05) inhibited basal and hCGstimulated secretion of estradiol. In conclusion, insulin, IGF-I, IGF-II, EGF, and TGFβ can modulate steroidogenesis in porcine theca cells.