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SUMMARY
Ovaries taken from rats in oestrus converted more [4-14C]testosterone to [14C]oestrone and [14C]oestradiol-17β than did ovaries taken at dioestrus. Little difference was found in the conversion of [4-14C]androst-4-ene-3,17-dione to [14C]oestrone by either type of tissue.
These results suggest that testosterone, rather than androstenedione, is an endogenous oestrogen precursor in the rat.
The ability of the rat ovary to produce oestrogen in vitro from C-19 steroids during dioestrus is discussed.
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SUMMARY
Secretion of oestrogen by the ovaries of foetal (15–19 days of gestation) and newborn rats in organ and tissue culture was not detectable by fluorometry when the ovary was taken from foetuses before folliculogenesis had occurred. In organ cultures of ovaries, the time of folliculogenesis corresponded with the normal timing of folliculogenesis in vivo. In tissue cultures the process of formation of follicles was delayed.
Oestrogens were present in the medium when folliculogenesis was fully established in the cultured foetal ovaries. Secretion began spontaneously and did not depend on the addition of gonadotrophins to the medium. The addition of gonadotrophins to the culture medium did not affect the level of oestrogen secreted by the foetal and newborn rat ovaries during the period of incubation (2–3 weeks).
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SUMMARY
Using incubation techniques, with progesterone as precursor, the capacity of the mouse ovary to form steroids was examined. Ovaries were taken from three groups of mice: (1) immature mice, (2) mature virgin females, (3) primigravid animals. The formation of the following steroids was suggested by the analytical methods used: 16-oxooestrone, 17-epioestriol, 17α-hydroxyprogesterone, 20α-hydroxyprogesterone, androstenedione, testosterone. Yields were very small from the ovaries of immature mice. The yields of oestrogens were greatest from ovaries of mature virgin females and of testosterone from those of pregnant mice. The factors contributing to the disappearance of the X zone of the adrenal gland during first pregnancy are discussed. It is concluded that one major factor is the secretion of testosterone by the ovary of the gravid mouse.
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SUMMARY
The metabolism of progesterone in the 1000 g supernatant fraction of homogenates of ovaries from PMSG-treated immature rats was determined. As early as 52 h after a single injection of 50 i.u. PMSG, still before the LH surge, 5α-pregnane-3α,20α-diol was identified as the main metabolite, together with smaller quantities of 3α-hydroxy-5α-pregnan-20-one and 5α-androstane-3α,17β-diol. Similar incubations of untreated rat ovaries at the same age did not produce 5α-pregnane-3α,20α-diol. The quantities of 3α-hydroxy-5α-pregnan-20-one and 5α-androstane-3α,17β-diol were reduced in PMSG-treated rat ovaries as compared with control ovaries. When progesterone metabolism was examined 64 h after PMSG administration, 5–7 h after the peak of the LH surge but still before ovulation, 75% of the substrate was converted to 5α-pregnane-3α,20α-diol, while 3α-hydroxy-5α-pregnan-20-one as well as 5α-androstane-3α,17β-diol could not be detected.
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19-Hydroxylation of the steroid molecule is an obligatory step in the conversion of androgens to oestrogens. It has been shown (Földes, Koref, Fehér & Steczek, 1964) that the urinary excretion of individual oestrogens decreases after the administration of 2-methyl-1,2-bis-(3-pyridyl)-1-propanone (SU4885).
The aim of the present communication is to show that SU 4885 inhibits the transformation of androstenedione to oestrogens in the rat ovary in vitro. The following trivial names are used: androstenedione = androst-4-ene-3,17-dione; oestradiol = oestra-1,3,5(10)-triene-3,17β-diol; oestrone = 3-hydroxy-oestra-1,3,5(10)-trien-17-one.
Female rats of the Wistar strain, weighing 180–250 g., received two injections of 50 units chorionic gonadotrophin (HCG, Choriogonin, Richter, Budapest) 24 and 16 hr. before the ovaries were removed. For each assay, 18 animals were used, six of which also received s.c. 10 mg. SU 4885 (Metopirone, Ciba, Basel) 40, 24 and 16 hr. before death. The ovaries were removed, halved and distributed (12 halved ovaries, 250–350 mg./vessel) between six vessels each
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Abstract
The activity of pro-oxytocin/neurophysin (pro-OT/Np)-processing enzymes was determined in human granulosa cells, follicular fluids and purified secretory granules of corpora lutea. We detected the presence of an endoprotease which releases OT-Gly10-Lys -Arg12 on cleavage of the synthetic pro-OT/Np(1–20) peptide after the dibasic Lys11-Arg12 doublet. This endoprotease was inhibited by EDTA, but was not affected by phenylmethanesulfonyl fluoride and pepstatin. Enzymatic activity was markedly reduced by replacement of l-Arg by d-Arg in the basic amino acid doublet of the substrate. The molecular weight of this enzyme was estimated to be 60 kDa. These features closely resembled those of the endoprotease identified in the bovine pituitary. The endoprotease is a metalloenzyme, specific for the Lys-Arg doublet. We also detected a carboxypeptidasic activity, inhibited by guanidinoethane-mercaptosuccinic acid. In the light of our previous detection of the processing intermediates, OT-Gly-Lys-Arg, OT-Gly-Lys and OT-Gly, in human ovary, these observations are in favour of a pro-OT/Np-processing pathway in the human ovary comparable with that in the bovine ovary. Moreover, these results confirm that oxytocin post-translational processing occurs in the human ovary and strongly suggest that pro-OT/Np is synthesized locally.
Journal of Endocrinology (1994) 142, 345–352
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assortment of gene expression in the mammalian ovary ( Espey & Richards 2002 , 2006 , Jo et al . 2004 , Rae et al . 2004 , McNatty et al . 2005 , Hernandez-Gonzalez et al . 2006 , Hourvitz et al . 2006 , Richards 2007 ). It is now clear this
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ABSTRACT
The effects of hysterectomy and ovariectomy on plasma concentrations of GH, somatomedin A, TSH and thyroxine (T4) were studied in developing rats. Four groups of 24-day-old rats were ovariectomized, ovohysterectomized, hysterectomized or sham-operated. Their weights, lengths and plasma hormone concentrations were measured at 26, 43, 64, 78 and 92 days of age to investigate pre- and postpubertal differences caused by the uterus or ovaries. Plasma concentrations of the hormones examined showed a successive rise with time, but GH and somatomedin A concentrations rose mainly after the opening of the vagina (days 50–55). Higher GH and somatomedin A concentrations were found in the plasma of ovariectomized animals than in ovohysterectomized controls before puberty (GH: 260–300%, P<0·01; somatomedin A: 25–30%, P<0·05). Ovariectomized animals weighed more than ovohysterectomized females after puberty (4·5–6%, P<0·01). This indicated that the uterus exerted a stimulatory effect on GH-somatomedin A regulation and body weight gain in the absence of the ovaries.
Significantly lower plasma somatomedin A (but not GH) concentrations were found in hysterectomized and sham-operated animals than in their respective controls after puberty (30–39%, P<0·01) and their final body weight was lower (22–26%, P<0·001). There were no consecutive uterus- or ovary-related changes in plasma TSH and T4 levels.
It was concluded that both the uterus and ovaries had significant as well as opposite effects on somatomedin A and body weight with the effects of the ovaries being greater than those of the uterus.
J. Endocr. (1987) 113, 21–26
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The binding of 125I-labelled human chorionic gonadotrophin (HCG) to ovarian tissue was studied in hypophysectomized immature and adult rats. The ability of the ovaries of adult rats to bind HCG was markedly reduced within 3 days of hypophysectomy and remained low for at least 20 days. The extent of the reduction depended on the stage of the oestrous cycle at which hypophysectomy was performed. The highest loss of HCG binding capacity was seen in rats hypophysectomized at dioestrus II, while rats hypophysectomized at the oestrous stage exhibited similar HCG binding to control rats at the same stage of the cycle. Scatchard analysis indicated that the reduction in the capacity of the ovary to bind HCG after hypophysectomy was caused by the loss of specific receptors and not by a decrease in binding affinity. In contrast to adult rats, in immature rats the HCG binding capacity of the ovaries did not change during the 3 days after hypophysectomy, but after this a slow decline took place. Twenty days after pituitary ablation, almost identical values for binding of HCG were found in immature and adult rats. Since hypophysectomy in adult rats causes a rapid regression of large follicles, our results indicate that the remaining HCG binding activity arises largely from small follicles which are known to be unaltered by the deprivation of hypophysial hormones. This assumption is supported by our observation that in the ovaries of 25-day-old immature rats, which lack large follicles, only a slow decrease in the ability of the ovaries to bind HCG occurs in the 20 days after the operation.
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betaglycan and ActRIIs co-expressed on the cell surface ( Phillips & Woodruff 2004 ). The avian ovary provides a unique model for the study of folliculogenesis as the single left ovary contains follicles of various sizes and developmental stages
