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Search for other papers by H M Fraser in
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Search for other papers by P F Whitelaw in
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Search for other papers by S G Hillier in
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Abstract
During the luteal phase of the primate ovulatory cycle the predominant inhibin/activin subunit mRNAs produced by the corpus luteum and antral follicles are those for the α- and βB-subunits respectively. The control of expression of these mRNAs and the resultant nature of the endocrine and paracrine signals which they may potentially generate has yet to be elucidated. Inhibin/activin subunit mRNAs may have a role in both the paracrine regulation of follicular and luteal function and modulation of FSH secretion. The aim of this study was to investigate the expression of inhibin/activin subunit mRNAs following luteal regression induced by either withdrawal of LH support (GnRH antagonist treatment), or by a direct inhibitory action (prostaglandin administration). Marmoset monkeys with regular ovulatory cycles were treated on day 8 and 9 of the luteal phase with either GnRH antagonist, prostaglandin or vehicle (n=3 per group). Ovaries were studied 48 h after onset of treatment (on day 10 of the luteal phase) by hybridizing frozen tissue sections with radiolabelled riboprobes specific to the inhibin/activin α-, βA- and βB-subunit mRNAs. After autoradiographic exposure, grain concentrations were quantified by image analysis. In corpora lutea from control marmosets there was high expression of α-mRNA with only marginal expression of βB-mRNA. Corpora lutea in animals treated with GnRH antagonist or prostaglandin had markedly reduced expression of α-mRNA while βB-mRNA was unchanged. In controls, all healthy antral follicles exhibited a high level of expression of βB-mRNA in the granulosa cells and low expression of α-mRNA in theca cells. This was unaffected by either treatment. βA-mRNA was found at a low level in granulosa cells but was not evident at a significant level in the corpora lutea of any of the groups. These results demonstrate (1) the marmoset corpus luteum is a source of high expression of α-subunit mRNA, (2) this α-mRNA is dependent upon LH support, (3) the process of luteal regression takes place without alteration of βB-mRNA. Antral follicle α- and βB-mRNAs are independent of the process of luteal regression or gonadotrophic withdrawal during the period of the luteal-follicular phase transition.
Journal of Endocrinology (1995) 144, 201–208
Search for other papers by M Tetsuka in
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Search for other papers by P F Whitelaw in
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Search for other papers by M R Millar in
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Search for other papers by C D Smyth in
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Search for other papers by S G Hillier in
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Abstract
Androgen receptor (AR) distribution and developmental regulation in the rat ovary were examined by semiquantitative immunohistochemistry. Ovarian AR mRNA levels were also determined by Northern analysis of total RNA and compared with the levels of cytochrome P450aromatase (P450arom), an established marker of preovulatory follicular maturity. Hypophysectomized immature female rats were treated with recombinant human (rh)-FSH and/or rh-LH, or human menopausal gonadotrophin (HMG). AR was predominately located in granulosa cells. There was no indication of specific AR immunoreactivity in thecal cells, but scattered stromal cells did stain positively. In control and LH-treated ovaries, only small preantral/early antral follicles were present. Granulosa cells in these follicles showed intense AR immunostaining. Treatment with FSH, FSH and LH or HMG stimulated varying degrees of preovulatory follicular development. In these follicles, the intensity of AR immunostaining progressively declined as follicular development progressed. In intact immature rats treated with FSH, the abundance of ovarian AR mRNA was significantly decreased to 35% of the control value while combined treatment of FSH and LH resulted in further down-regulation of AR mRNA expression to 17% of the control value. A decrease in the abundance of AR mRNA was accompanied by a simultaneous increase in the abundance of P450arom mRNA. Similar results were obtained in hypophysectomized immature rats treated with FSH and LH, suggesting an inverse relationship between AR mRNA expression and granulosa cell maturity. These results suggest that (1) the AR is most abundant in the granulosa cells of rat ovaries and (2) the expression of AR and its mRNA are developmentally regulated, being down-regulated during FSH-stimulated preovulatory follicular development.
Journal of Endocrinology (1995) 145, 535–543
