Immunoreactive cytochrome P-450(17 alpha) in rat and guinea-pig gonads, adrenal glands and brain

The cytochrome P-450(17 alpha)-hydroxylase, 17----20 lyase (P-450(17 alpha)) is the key enzyme responsible for the biosynthesis of androgens in steroidogenic organs. Its cellular localization has been examined with an immunohistochemical technique. In immature rat ovary, P-450(17 alpha) was first detected in sparse interstitial cells on postnatal Day 8. The number of immunoreactive interstitial cells increased thereafter and the intensity of P-450(17 alpha) staining in these cells was highest at 3 weeks of age. The intensity of staining then started to decline and was very faint at Day 35. From 6 weeks on, the distribution of immunoreactive P-450(17 alpha) was of the adult type: it was detected exclusively in the thecal cells of the large antral, preovulatory, follicles. P-450(17 alpha) was not detectable during pregnancy except on the day of parturition, when thecal cells were transiently immunoreactive. The staining had vanished 24 h after delivery. Human chorionic gonadotrophin (hCG), injected into immature females on Days 24 to 26, induced P-450(17 alpha) prematurely in thecal cells. When injected on Days 12 to 14 of pregnancy, hCG also induced P-450(17 alpha) in the thecal cells surrounding the largest follicles, whereas the interstitial and luteal cells were not immunostained. The antiprogestin RU486, injected on Day 16 of pregnancy, reinstated P-450(17 alpha) (and P-450scc) immunoreactivity in the thecal cells. Oestradiol selectively suppressed P-450(17 alpha) expression in the thecal cells of RU486-treated females. In immature guinea-pig ovary, P-450(17 alpha) was immunostained in thecal cells, not in interstitial cells, although the interstitial cells expressed the delta 5-3 beta-hydroxysteroid dehydrogenase. P-450(17 alpha) was also immunolocalized in the Leydig cells of rat and guinea-pig testes, and in the guinea-pig adrenal cortex (zonae fasciculata and reticularis), but not in the rat adrenal cortex. P-450(17 alpha) was not detectable in the brain of either rat or guinea-pig.

Cell-specific variations and hormonal regulation of immunoreactive cytochrome P-450scc in the rat ovary

Specific rabbit antibodies to the bovine cholesterol side-chain cleavage cytochrome P-450 (P-450scc) were used to cross-react with the enzyme in the rat ovary. The luteal cells of cyclic, pregnant, and pseudopregnant rats were immunostained. P-450scc was also expressed in the interstitial cells of prepubertal and cyclic adult rats, and in the thecal cells lining the preovulatory follicles. In cyclic females, RU 486 and oestradiol increased the intensity of P-450scc immunostaining. The granulosa cells of ovarian follicles whatever their stage of development, including preovulatory follicles, were not labelled, except after ovulation. The intensity of immunostaining of thecal and interstitial cells decreased during early pregnancy or pseudopregnancy, and disappeared after Day 9, whereas these cells were intensely labelled 24 h after parturition. The immunostaining of thecal and interstitial cells was again detected in 18-day pregnant rats, treated with the antiprogesterone RU 486. It is therefore concluded that both oestradiol and progesterone are involved in P-450scc regulation.

Neurosteroids: cytochrome P-450scc in rat brain

The steroid hormones corticosterone and testosterone are supplied to the central nervous system by endocrine glands, the adrenals and gonads. In contrast, the 3 beta-hydroxy-delta 5-derivatives of cholesterol, pregnenolone and dehydroepiandrosterone, accumulate in the rat brain through mechanisms independent of peripheral sources. Immunohistochemical studies have been performed with specific antibodies to bovine adrenal cytochrome P-450scc, which is involved in cholesterol side-chain cleavage and pregnenolone formation. The enzyme was localized in the white matter throughout the brain. Scarce clusters of cell bodies were also stained in the entorhinal and cingulate cortex and in the olfactory bulb. These observations strongly support the existence of "neurosteroids," which have been posited on the basis of biochemical, physiological, and behavioral studies.

Alkaline phosphatase activity in the membrane of Xenopus laevis oocytes: effects of steroids, insulin, and inhibitors during meiosis reinitiation

The mechanism of steroid hormone-induced reinitiation of meiosis in Xenopus laevis oocytes in vitro involves interaction of the hormone with an ooplasma membrane receptor and early changes of enzymatic activities (adenylate cyclase, p48 protein kinase). In full-grown (stage 6) oocytes, we have observed cytochemically, at the ultrastructural level, alkaline phosphatase activity in the ooplasma membrane of microvilli, its decrease by 2 hr of progesterone action, and its complete disappearance at the time of germinal vesicle breakdown (GVBD). Insulin (30 micrograms/ml) also provoked a decrease of phosphatase activity, although it did not promote GVBD under these circumstances. When oocytes were exposed simultaneously to progesterone (1 microM) and insulin (30 micrograms/ml), the enzymatic activity disappeared earlier than with any one of them, correlating with the faster occurrence of GVBD. Inhibitors of alkaline phosphatase activity and competitive substrates potentiated progesterone action on GVBD. Insulin and beta-glycerophosphate potentiating activities were additive. These results suggest that the ooplasma membrane alkaline phosphatase may be implicated in the course of reinitiation of meiosis in X. laevis oocytes.

Testosterone-induced meiotic maturation of Xenopus laevis oocytes: evidence for an early effect in the synergistic action of insulin

Meiosis reinitiation in oocytes (stage 5-6 of Dumont) isolated free of follicle cells by collagenase treatment from ovarian pieces of Xenopus laevis, was studied in observing the germinal vesicle breakdown (GVBD) provoked by progesterone and testosterone (0.1 nM-1 microM), alone or in association with insulin (30 micrograms/ml). Testosterone, was more active than progesterone to elicit GVBD in vitro, raising the question of the relative roles of both steroids in the physiological maturation process in vivo. The potentiating effect of insulin, already observed on progesterone action, was also demonstrated upon testosterone effect; the results suggested that it occurs during the early phase of hormone-induced meiosis reinitiation.

A role for prostaglandins in decidualization of the rat uterus

The deciduogenic action of various kinds of prostaglandin (PG), i.e. PGE1, PGE2, PGF2 alpha and PGI2, methylated prostaglandins (15-met-PGE1, 15-met-PGE2 and 15-met-PGF2 alpha), PGF2 alpha-13-dehydro analogues (13-DH-PGF2 alpha, ent-15-epi-13-DH-PGF2 alpha), endoperoxide analogues (15S)-hydroxy-9 alpha,11 alpha-(epoxymethano)-prosta-5Z,13E-dienoic acid (U 44069) and (15S)-hydroxy-11 alpha,9 alpha-(epoxymethano)-prosta-5Z, 13E-dienoic acid (U 46619), and of the prostaglandin precursor, arachidonic acid, has been demonstrated after intraluminal instillation of these compounds into the uterus of immature rats sensitized with progesterone alone. Under this minimal hormonal stimulation, in which a trauma (a scratch) of the endometrium is required to induce the decidual response, all these compounds elicited the formation of deciduomata, substantiating the suggestion that the scratch-induced decidual reaction is mediated through release of prostaglandin. Confirmation was obtained through the effect of indomethacin and cortisol, both of which decreased the decidual response brought on by a scratch or by arachidonic acid, whereas the effect of PGF2 alpha was decreased by indomethacin but not by cortisol. Histamine, thromboxane B2, and oleic, palmitic and homo-gamma-linolenic acids were not deciduogenic. A dose-dependent inhibitory effect of indomethacin on deciduoma formation by instillation of oil into animals sensitized by progesterone plus oestradiol was also observed. The results support the proposal that the decidual reaction involves prostaglandins and we suggest that the deciduoma is a valuable model for studying the action of prostaglandin-related compounds.

Treatment of neonatal rats with progesterone alters the capacity of the uterus to form deciduomata

Progesterone, given to rats on Days 7-9 after birth, abolishes the capacity of the adult uterus to form a deciduoma. Treatment on Days 3-5 reduces the response and on Days 13-15 has no effect.

In vitro decidualization of rat endometrial cells

Rat endometrial cells were isolated from ovariectomized adults submitted to a progesterone-estradiol sequence proper to sensitize the uterus to respond to a deciduogenic stimulus, and then cultured in vitro in the presence of progesterone. They grew rapidly and became morphologically similar to the decidual cells occurring in vivo with regard to the binucleation and the accumulation of characteristic filamentous material in the cytoplasm. The life-span of the decidualized cells in vitro was comparable to the duration of the deciduoma in vivo. The progesterone treatment of the rat was found to be a prerequisite for such development and transformation of endometrial cells in vitro, since control experiments performed with nonhormonally injected castrated animals gave only isolated islets of epithelial cells and scattered fibroblast-like cells in culture, whereas the decidual transformation was still observed, although with some delay, with cells from progesterone (but not estradiol)-treated spayed rats. Such an in vitro system may provide a new opportunity to study the mechanism of decidualization and of its hormonal control.