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-beta (TGF beta), 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 x 10(5) cells/ml.well) in serum-free M199, treated with increasing doses of growth factors: IGF-1 (0.1-50 ng/ml), IGF-II (0.5-200 ng/ml), EGF (0.021-100 ng/ml), TGF beta (0.001-40 ng/ml), or insulin (0.01-50 micrograms/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 less than 0.05) basal and gonadotropin-induced secretion of androstenedione, progesterone, estradiol, and testosterone. IGF-I increased (P less than 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 less than 0.05) thecal steroidogenesis, but only after administration of hCG. In contrast, TGF beta increased (P less than 0.05) basal and gonadotrophin-induced 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 less than 0.05) inhibited basal and hCG-stimulated secretion of estradiol. In conclusion, insulin IGF-I, IGF-II, EGF, and TGF beta can modulate steroidogenesis in porcine theca cells.

Prostaglandin F2α-Induced Functional Regression of the Corpus Luteum and Apoptosis in Rodents

“…TGFb alters the capacity of steroidogenesis directly (27,28) and localizes in the corpus luteum in rats (29) and humans (30) in addition to the theca / interstitial cells of rats (28). Induction of apoptosis in ovarian thecal and interstitial cells is enhanced by combined treatment with TGF-a and TGF-b (31,32); the changes are accompanied by the increased expression of interleukin1b converting enzyme (caspase-1) mRNA 5 h after the combined treatment.…”

Regulation of Sterol Regulatory Element-Binding Transcription Factor 1a by Human Chorionic Gonadotropin and Insulin in Cultured Rat Theca-Interstitial Cells1

“…The stimulatory effect of luteinizing hormone (LH) and insulin on androgen production by T-I cells has been well established [5][6][7][8][9][10][11][12][13][14]. Because cholesterol is the precursor of androgens, its availability in T-I cells, either by uptake from plasma-derived cholesterol or through de novo synthesis, has been shown to have an important role in androgen synthesis [11,15].…”

Luteinization and proteolysis in ovarian follicles of Meishan and Large White gilts during the preovulatory period

“…The lack of increase in amounts of TIMP-1 after hCG administration contrasts with another report in pigs (Smith et al, 1994 (Fowlkes et al, 1994). The resulting high amounts of IGF-I released from IGFBP would then stimulate progesterone production by ovarian cells more efficiently in Meishan follicles (Caubo et al, 1989;Urban et al, 1990). …”