Effects of estradiol on bovine thecal cell function in vitro: dependence on insulin and gonadotropins.
The objective of this study was to evaluate the influence of estradiol (E2) on proliferation and steroid production by thecal cells obtained from large (> or =8 mm) follicles of cattle. Five experiments evaluated the effect of various doses of E2 during a 2-d exposure in serum-free medium on hormone-induced steroidogenesis and cell proliferation. In LH-treated thecal cells of experiment 1, 300 ng/mL of E2 decreased progesterone production by 30% and increased androstenedione production to 5.8-fold of controls. In the absence of LH, both 3 and 300 ng/mL of E2 increased progesterone production. In experiment 2, in the presence of insulin and LH, 3, 30, and 300 ng/mL of E2 decreased progesterone production (by 17 to 36%), whereas 3 ng/mL of E2 decreased and 300 ng/mL of E2 increased androstenedione production. Doses of LH (3 to 30 ng/mL) tested in experiment 3 increased (to as much as 3.7-fold) progesterone production by thecal cells and E2 attenuated this stimulatory effect by 40%. In contrast, E2 amplified the stimulatory effect of LH on androstenedione production in experiment 3. In experiment 4, E2 (300 ng/mL) decreased IGF-I- and insulin-induced thecal cell progesterone production by 70 to 77%, whereas E2 increased basal, IGF-I, and insulin-induced androstenedione production. In experiment 5, in the presence of insulin, 10 to 1000 ng/mL of E2 had no effect on [(125)I]-IGF-I binding to thecal cells, whereas 10 and 100 ng/mL of E2 increased and 1000 ng/mL of E2 decreased progesterone production by thecal cells. Estradiol had no consistent effect on thecal cell numbers among the 5 experiments. These results support the hypothesis that E2 may act as a paracrine factor to directly regulate hormone-induced steroid production by thecal cells without affecting cell numbers or numbers of insulin-like growth factor type I receptors.
Spicer
L J
LJ
Department of Animal Science, Oklahoma State University, Stillwater, 74078, USA. igf1Leo@okstate.edu
D000735:Androstenedione / Q000096:biosynthesis; D000818:Animals; D002417:Cattle; D002452:Cell Count; D002478:Cells, Cultured; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology*; D011374:Progesterone / Q000096:biosynthesis; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000502:physiology; D013799:Theca Cells / Q000187:drug effects* / Q000502:physiology*
D007328:Insulin; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D017526:Receptor, IGF Type 1