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SUMMARY
The amount of oestrogen produced by immature mouse ovaries cultured with purified gonadotrophins was measured by means of a radioimmunoassay. Small quantities were released in response to FSH or LH alone, but when both were provided production was greatly enhanced after an initial lag phase of 2–3 days. The lowest concentrations required to produce this synergistic effect were between 0·02 and 0·13 i.u. FSH/ml and between 0·01 and 0·1 i.u. LH/ml. After prolonged exposure to 0·4 i.u. FSH/ml plus 1·0 i.u. LH/ml, oestrogen output continued to rise until, on the ninth day of culture, it reached 2·6–7·3 ng/ ovary/day. Pre-treatment with 0·4 i.u. FSH/ml for 3 days enhanced the subsequent response to combined gonadotrophins but the simultaneous presence of FSH and LH was essential for inducing the delayed synergistic effect. Although both gonadotrophins also stimulated follicle growth there was no evidence suggesting any simple correlation between that response and oestrogen synthesis. Maximal oestrogen production coincided with very low follicular mitotic activity.
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SUMMARY
Sections of ovaries from 30 Swiss white mice were incubated with ten steroid substrates to demonstrate 3β-hydroxysteroid dehydrogenase activity histochemically. The substrates were: (1) 3β-hydroxypregn-5-en-20-one (pregnenolone), (2) 3β,17α-dihydroxypregn-5-en-20-one (17α-hydroxypregnenolone), (3) 3β-hydroxyandrost-5-en-17-one (DHA), (4) 3β,17β-dihydroxyandrost-5-ene (androstenediol), (5) 3β-sulphoxypregn-5-en-20-one (pregnenolone sulphate), (6) 3β-sulphoxy-17α-hydroxypregn-5-en-20-one (17α-hydroxypregnenolone sulphate), (7) 3β-sulphoxyandrost-5-en-17-one (DHA sulphate), (8) 3β-acetoxypregn-5-en-20-one (pregnenolone acetate), (9) 3β-acetoxyandrost-5-en-17-one (DHA acetate), and (10) 3β-acetoxy-17β-hydroxyandrost-5-ene (androstenediol acetate).
Pregnenolone, 17α-hydroxypregnenolone, DHA and androstenediol gave a colour reaction in the corpora lutea, interstitial tissue, theca interna and stroma of all ovaries examined. The granulosa of many follicles, some thought to be atretic, also contained diformazan granules. 17α-Hydroxypregnenolone did not give as intense a reaction as the other free steroids.
No diformazan was deposited with DHA sulphate as substrate. Pregnenolone sulphate and 17α-hydroxypregnenolone sulphate were used by the same tissues as were the free steroids, although they were much less well utilized.
Utilization of 3β-acetoxy derivatives was similar to that of the free steroids.
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Polycystic ovary syndrome (PCOS) is a common but complex endocrine disorder and is a major cause of anovulation and consequent subfertility. It is also associated with a metabolic disturbance, characterized by hyperinsulinaemia and insulin resistance that carries an increased risk of type 2 diabetes in later life. Despite its prevalence little is known about its aetiology, but there is increasing evidence for an important genetic involvement. On the basis of experimental observations in the prenatally androgenized sheep and rhesus monkey, and supported by data from human studies, we propose that the clinical and biochemical features of PCOS can arise as a consequence of genetically determined hypersecretion of androgens by the ovary during, or very likely long before, puberty. The resulting hyperandrogenism results in 'programming' of the hypothalamic-pituitary unit to favour excess LH secretion, and encourages preferential abdominal adiposity that predisposes to insulin resistance. The severity of hyperinsulinaemia and insulin resistance (which has a profound influence on the phenotype of PCOS) is further influenced by both genetic factors (such as polymorphism in the insulin gene regulatory region) and environmental factors, notably obesity. This hypothesis therefore suggests a unifying, 'linear' model to explain the aetiology of the heterogeneous phenotype.
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SUMMARY
The rate of synthesis of [14C]oestrone and [14C]oestradiol-17β from [14C]testosterone in vitro by ovaries from rats at different stages of the oestrous cycle was measured. The rate of [14C]oestrogen synthesis was highest in ovaries taken from rats in pro-oestrus and lowest in ovaries taken from rats early in the dioestrous phase of the cycle. Rates of synthesis in ovaries obtained from rats in the late dioestrous stage were intermediate between the rates of the other groups. The rates of [14C]oestrogen synthesis at these periods of the cycle paralleled the concentrations of oestrogens in ovarian vein plasma reported by other authors.
Gonadotrophin preparations with either luteinizing hormone activity or both follicle-stimulating hormone and luteinizing hormone activities had no effect on [14C]oestrogen synthesis by rat ovaries in vitro at any of these stages of the oestrous cycle.
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While the disciplines of reproduction and immunology have traditionally been seen to be discrete and separate areas of biology, there is now compelling evidence of an intimate relationship between the cells of the reproductive tract and those of the immune system. White cells are found throughout the uterus, Fallopian tubes and ovary, and change in numbers and subtypes throughout the reproductive cycle (Bulmer et al. 1991). In the uterus, leukocytes congregate at the implantation site and successful conception leads to alteration of the maternal immune system (Hill 1990). For clinical purposes, the importance of immune activation is identified in two relevant hypotheses. The first, the immunotrophism hypothesis of Wegmann and colleagues (Wegmann 1988, Beaman 1990), states that products of T lymphocytes in the uterus promote implantation and embryonic development through stimulation of the proliferation and function of the trophoblast cells. The second, promoted by Hill (1990) and termed the immunodystrophism
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The classic endocrine function of ovarian inhibin is negative feedback control of pituitary FSH secretion (see de Jong, 1988 for a review). There is, however, a long-harboured suspicion that inhibin and related proteins such as activin could have local regulatory roles at or near their sites of formation in the gonads (e.g. Ying, 1988). Here, I survey recent developments in inhibin and activin research which support this likelihood, proposing paracrine functions for both proteins in the regulation of preovulatory follicular development and oestrogen synthesis in human ovaries.
Inhibin, activin and related regulatory proteins
Mature inhibin is a 32 kDa glycoprotein which has been isolated from ovarian follicular fluid as two distinct forms composed of a common α-subunit and one of two β-subunits, βA and βB (Ling, Ying, Ueno et al. 1985; Miyamoto, Hasegawa, Fukuda et al. 1985; Rivier, Spiess, McClintock et al. 1985; Robertson, Foulds, Leversha et al
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ABSTRACT
In the mouse, follicular formation and development is largely postnatal. Changes in ovarian steroidogenesis during early postnatal life are likely, therefore, to reflect changes in follicular activity during early folliculogenesis. In this study, basal progesterone and androstenedione production and responsiveness to gonadotrophins, dibutyryl cyclic AMP (dbcAMP) and 22R-hydroxycholesterol have been measured following short-term in-vitro incubations of ovaries from mice aged 1, 3, 5, 7, 10 or 15 days. On the day of birth (day 1), basal and gonadotrophin-stimulated progesterone and androstenedione production were undectectable although a response to dbcAMP and a low level of cholesterol side-chain cleavage (CSCC) activity (measured using 22R-hydroxycholesterol) were present. On day 3 progesterone and androstenedione production were undetectable under all conditions. On day 5 only a low level of CSCC activity was detectable but on day 7 there was an increase in ovarian steroid production. Basal progesterone and androstenedione were detectable and LH, but not FSH, increased the production of both steroids. These changes were associated with a marked increase of more than 80-fold in CSCC activity. Basal steroid output increased from days 7 to 15 and LH continued to stimulate progesterone accumulation although no effect on androstenedione was seen. Addition of FSH had no effect on steroidogenesis on day 10 but significantly increased progesterone production on day 15. Ovaries from the mice used in these studies contained primordial follicles and stromal tissue on day 1. By day 5 primary and secondary follicles were present and the major increase in steroid production between days 5 and 7 was associated with an increase in secondary follicles and increased differentiation of the thecal tissue. These results show that there is a major increase in ovarian steroidogenesis at day 7 in the mouse and suggest that during folliculogenesis significant gonadotrophin-sensitive steroidogenesis may first be seen in the thecal tissue of the secondary follicle.
Journal of Endocrinology (1991) 130, 101–106
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-priming) in the cyclic rat. In addition, the involvement of the ovary in the hFSH-suppressed LH secretion was evaluated using ovariectomized (OVX) rats in metoestrus. Materials and Methods Animals, general conditions and surgery Adult female Wistar rats
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While physiological and biochemical data show that the testes of neonatal rats release androgenic substances capable of influencing morphogenesis and behavioural potentiality, equivocal evidence is available concerning the secretory capacity of the ovaries during this period. Presi, Jirásek, Horský & Henzl (1965) reported no detectable steroid-3β-ol dehydrogenase in interstitial cells around follicles in rats less than 8 days old. Using a bioassay method, Cierciorowska & Russfield (1968) found no reliable activity in ovarian extracts from rats younger than 13 days. Fluorometric analyses also failed to reveal significant amounts of oestrogen in ovaries from rats younger than 10 days (Presl, Hermann & Horský, 1969). Since Carmichael & Marshall's (1908) research, it is known that unilateral ovariectomy is followed by hypertrophy in the remaining ovary, presumably resulting from increased circulating gonadotrophin associated with decreased negative feedback by ovarian hormone. If the ovary of the neonatal rat does not secrete active hormones, then
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Δ5-3β-Hydroxysteroid dehydrogenase is a key enzyme involved in steroidogenesis, and has been demonstrated histochemically in the ovaries of a number of species (Baillie, Ferguson & Hart, 1966). The histochemical technique requires the addition of NAD and steroid substrate to the incubation medium, and the presence in the cellular structure of NADH2-dehydrogenase for the effective transfer of hydrogen to the tetrazolium dye (Wattenberg, 1958). Since monkey ovaries were available to us, it was decided to examine them for both NADH2-dehydrogenase and Δ5-3β-hydroxysteroid dehydrogenase. No previous reports have appeared on the localization of these enzymes in the ovaries of the monkey.
Six rhesus monkeys (Macaca mulatta) were investigated, two of which were pregnant (52 and 58 days p.c.). Only one of the pair of ovaries from each of the pregnant animals was available for this investigation. The non-pregnant animals were bilaterally ovariectomized on day
