Independence of Steroidogenic Capacity and Luteinizing Hormone Receptor Induction in Developing Granulosa Cells*

Abstract

The relationship between FSH-induced acquisition of LH/hCG receptors and the steroidogenic capacity of granulosa cells from estrogen-primed hypophysectomized rat ovaries has been examined. Granulosa cells harvested from the immature preantral follicles of animals not treated with FSH (controls) displayed negligible specific human [125I]iodo-hCG binding and produced only minimal amounts of progesterone during 48 h of culture in vitro. Addition of highly purified hFSH or prostaglandin-E2 (PGE2) to the culture medium elicited substantial increases in progesterone production which were not accompanied by measurable increases in [125I]iodo-hCG binding. Treatment with oFSH in vivo for 24 h led to the initiation of antrum formation in many follicles and was accompanied by an 8-10-fold increase in hCG binding by freshly isolated granulosa cells. Basal, hFSH-, and PGE2-stimulated progesterone production during culture was also greater than controls. In contrast, cells from animals receiving oFSH in vivo for only 12 h showed no increase in hCG binding either before or after culture, yet basal and stimulated progesterone production in vitro was significantly greater than controls, indicating that the initiation of steroidogenesis was antecedent to LH/hCG receptor induction. Only those cells obtained after the 24-h in vivo treatment with oFSH produced elevated amounts of progesterone when incubated in the presence of hCG, thereby showing that the observed increases in [125I]iodo-hCG binding reflected the induction of functionally active LH/hCG receptors. Pharmacological stimulation of steroidogenesis by cell suspensions with N,O'-dibutyryl cAMP resulted in consistently high levels of progesterone production irrespective of previous treatment with FSH in vivo. This uniform expression of in vitro steroidogenic capacity occurred in the complete absence of measurable increases in LH/hCG receptors, suggesting that these two fundamental developmental processes are independent phenomena which may be under separate regulation in vivo.

Hormonal regulation of preovulatory follicle maturation in the rat

“…Short-term incubations of whole follicles gave similar results (Hillier et al, 1978). Thus the action of FSH on steroidogenesis is mediated by the activation or sensitization of a biochemical step(s) located distally to the primary membrane effector interaction and the locus of cAMP production (Hillier et al, 1978). Histochemical studies of steroidogenic enzymes in the ovaries of adult rats during the oestrous cycle suggest that 3ß-hydroxysteroid dehydrogenase activity in the granulosa cells of maturing follicles increases as the cycle proceeds, becoming apparent in some of the larger growing follicles on the 2nd day of dioestrus and increasing markedly by pro-oestrus (Pupkin, Bratt, Weisz, Lloyd & Balogh, 1966).…”

“…2) led to readily detectable basal secretion of progesterone (no additions to culture medium) which was stimulated 3-4-and 1-6-fold after 240 min in the presence of FSH and dibutyryl cAMP, respectively. Short-term incubations of whole follicles gave similar results (Hillier et al, 1978). Thus the action of FSH on steroidogenesis is mediated by the activation or sensitization of a biochemical step(s) located distally to the primary membrane effector interaction and the locus of cAMP production (Hillier et al, 1978).…”

“…In preantral follicles, LH binds to and acts specifically on thecal and interstitial cells (Zeleznik et al, 1974), but does not bind to the granulosa cells (Channing & Kammerman, 1973; Lee, 1976;Hillier, Zeleznik & Ross, 1978 Louvet et al (1975b) and .…”

“…An examination of the relationship between FSH-induced LH/hCG receptors and the steroidogenic capacity of granulosa cells of oestrogen-primed hypophysectomized rats showed that early antrum formation following treatment with FSH for 24 h was associated with marked increases in both steroidogenic potential and binding of 125I-labelled hCG in vitro (Hillier et al, 1978 (Baird & Fraser, 1975;Makris & Ryan, 1975). The classical experiments of Falck (1959) (Fortune & Armstrong, 1977 Granulosa cell suspensions were prepared from the ovaries of 27-day-old oestrogen-primed hypophysectomized rats injected with saline (9 g NaCl/1) or 100 µg oFSH (LER-1698) …”

Effects of oestradiol-17 beta and testosterone on progesterone production in the cultured granulosa cells of Japanese quail

“…It is widely accepted that the pituitary gonadotrophins, LH and follicle stimulating hormone (FSH), play an essential role in progesterone production by granulosa cells (Hillier et al, 1978;Li and Johnson, 1993), and this process might be modulated by steroid hormones such as oestradiol-17b and testosterone, which are the main sex steroids produced by the theca cells of the developing follicles (Hutz, 1989). Armstrong (1984) showed that a substantial amount of oestradiol-17b is secreted from the theca cells of immature follicles which have high aromatase activity.…”