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Introduction Ovarian antral follicles require gonadotropin stimulation for development and ovulation whereas preantral follicles seem capable of development in the absence of follicle-stimulating hormone (FSH) and luteinizing hormone (LH
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Brain Health Research Centre, University of Otago, Dunedin, New Zealand
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primordial follicles leads to transition to the primary stage. Subsequent progression through the preantral stages is facilitated by oocyte growth and proliferation of the associated granulosa and theca cells. The antral stages are characterized by the
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ABSTRACT
In-vivo changes in steroidogenesis in preantral hamster follicles following exposure to the LH surge could be mimicked by stimulation with exogenous LH in vitro. Luteinizing hormone given only during the first hour (media were changed every hour) of a 6-h incubation promptly increased the concentration of androstenedione and adenosine 3′:5′-monophosphate (cAMP) in the media and this was followed by a gradual decline to <20% of the peak value; progesterone in media was not detectable with a single LH stimulation. However, LH given every hour increased progesterone and cAMP concentrations in the media throughout the period of incubation, but the transient increase and subsequent decline in androstenedione was still observed. The decline in androstenedione release by preantral follicles was apparently due to a lack of steroid precursor and not to either inhibition of hydroxyl-lyase or lack of LH or cAMP stimulation. Exogenous dibutyryl cAMP (dbcAMP) and 8-Br-cAMP mimicked the effects of LH on the pattern of follicular androstenedione release into the media; however, dbcAMP and 8-Br-cAMP did not increase concentrations of progesterone in vitro. In preantral follicles, LH stimulated cAMP release into the media and apparently inhibited phosphodiesterase activity, since methyl isobutylxanthine (MIX) did not potentiate the effect of LH on cAMP. Follicle-stimulating hormone also increased androstenedione and cAMP in the media of the preantral follicles in a manner similar to that of LH, except that between 4 and 6 h of incubation the release of androstenedione and cAMP was less than that produced by stimulation with LH. Interestingly, FSH and MIX stimulated androstenedione and cAMP release by preantral follicles in a manner similar to that induced by LH alone.
These results indicate that LH stimulation of preantral follicles in vitro induces an androstenedione– progesterone shift which is mediated by cAMP. The decline in androstenedione release by the preantral follicle in vitro appears to be due to a lack of appropriate steroid precursors and not to an inhibitory action of LH on androgen synthesis.
J. Endocr. (1987) 114, 55–63
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ABSTRACT
The present study describes the acute changes in steroids and human chorionic gonadotrophin (hCG) and FSH binding of preantral follicles induced by the gonadotrophin surges on the day of pro-oestrus. Preantral follicles were isolated by microdissection before (09.00–10.00 h), during (15.00–16.00 h) and after (21.00–22.00 h) the LH surge on pro-oestrus. Follicles at each time-period were pooled and steroid concentrations and gonadotrophin receptors determined. Before the LH surge, concentrations of progesterone and androstenedione were 40·8 ± 6·1 (s.e.m.) and 10·7 ± 3·9 fmol/follicle respectively. At the peak of the LH surge, progesterone and androstenedione concentrations in preantral follicles increased to 848 ± 186 and 129 ± 33 fmol/follicle respectively. Immediately after the LH surge, progesterone increased to 1238 ±97 fmol/follicle whereas androstenedione declined to 13·3 ±2·1 fmol/follicle. Oestradiol was less than 6 fmol/follicle throughout these periods. Binding of hCG and FSH to preantral follicles increased after the surge (hCG, 56± 2·6 c.p.m./follicle; FSH, 29·8 ± c.p.m./follicle) when compared with values obtained before the surge (hCG, 15·8± 4·0 c.p.m./follicle; FSH, 14·1 ± 1·9 c.p.m./follicle). Also, hCG binding increased significantly (P<0·05) from 09.00 to 21.00 h (56 ±2·6 c.p.m./follicle).
In order to ascertain which follicular compartments were affected by the LH and FSH surges on pro-oestrus, granulosa cells and thecae from preantral follicles were isolated and steroid concentrations and LH and FSH binding measured. Both thecal and granulosal concentrations of androstenedione were significantly (P<0·01) higher at the peak of the LH surge (15.00 h) than at 09.00 h (before the surge) and 21.00 h (after the surge). The granulosal concentration of progesterone was lowest at 09.00 h, highest at 15.00 h and remained increased at 21.00 h. Thecal progesterone concentrations did not increase significantly until 21.00 h at pro-oestrus. Binding of hCG to theca increased significantly (P<0·01) at 15.00 and 21.00 h when compared with values at 09.00 h. Binding of FSH to theca was not detected at 09.00 h and was low at 15.00 and 21.00 h. Binding of hCG and FSH to granulosa cells did not change significantly throughout this period on pro-oestrus.
These results indicate that the gonadotrophin surges on pro-oestrus induce significant stepwise increases in thecal LH binding in preantral follicles and that these coincide with parallel increases in follicular progesterone. Thus the gonadotrophin surges on pro-oestrus may be a signal regulating the onset of steroidogenesis and growth of preantral follicles.
J. Endocr. (1987) 114, 49–54
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ABSTRACT
The neonatal rat ovary is completely devoid of antral follicles until the twelfth day of age. During this period the ovary becomes steroidogenically active and responsive to gonadotrophins. The aim of this study was to correlate the onset of ovarian androgen and oestrogen production in vitro with the first appearance of distinct granulosa and theca cells. Although ovarian aromatase activity increased significantly on day 7 of age, ovarian oestrogen production was limited by low progesterone and testosterone production until day 12 of age. Increased aromatase activity on day 7 and androgen production on day 12 were coincident with the first appearance of granulosa and theca cells respectively. These functional and morphological changes were not associated with significant alterations in ovarian weight or concentrations of LH or FSH in serum.
J. Endocr. (1986) 110, 87–92
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–14 days postnatal (dpn), reaching about five-fold those found in adult cycling females ( François et al. 2017 ). We demonstrated that such FSH concentrations are necessary to induce Cyp19a1 aromatase expression in immature follicles at the preantral
Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Department of Mathematics, Imperial College London, London SW7 2AZ, UK
Laboratory of Neuroendocrinology, Department of Neurobiology, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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reflects the arrest of follicle development in the late antral stages but recent work from our group ( Webber et al. 2003 ), and that of Erickson and colleagues ( Maciel et al. 2004 ), has highlighted a disorder of early, preantral follicle development
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three layers of cuboidal granulosa cells. Pre-antral: an oocyte surrounded by more than three layers of granulosa cells with no apparent antrum. Antral: an oocyte surrounded by multiple layers of granulosa cells with an antrum. Unknown follicles
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), chondrocytes ( Eguchi et al. 2001 ), vascular smooth muscle cells ( Fan et al. 2000 ) and renal mesengial cells ( Goppelt-Struebe et al. 2001 ). We previously showed that rat granulosa cells in preantral and early antral follicles abundantly
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Institute, Cary, NC, USA). Results Immunohistochemistry revealed the presence of FGF17 predominantly in oocytes and granulosa cells of preantral and antral follicles ( Fig. 1 ). Staining was predominant in the nucleus of oocytes in preantral follicles, and
