Abstract

The mode of FSH actions within the testis was studied in immature hypophysectomized male rats by treatment with recombinant human FSH (recFSH, Org 32489). To elucidate the involvement of Leydig cells and androgens in the maintenance of spermatogenesis in FSH-treated hypophysectomized rats further, the recFSH treatment was given both alone and after destruction of Leydig cells with ethane-1,2-dimethane sulphonate (EDS). Three days after hypophysectomy (at 31 days of age) the rats were given one i.p. injection of vehicle or EDS and, 4 days later, they were implanted with osmotic minipumps releasing either 0·9% (w/v) NaCl or 1 IU recFSH/day.

Recombinant FSH alone increased testicular weights 2·5-fold in 7 days (P<0·01). The effect of FSH was similar in EDS-pretreated rats (P<0·01). Testicular testosterone increased from 6·5 ± 1·6 to 16·9 ± 5·3 (s.e.m.) pmol/g tissue (P<0·05) and serum testosterone from 0·12 ± 0·02 to 0·22 ± 0·03 nmol/l (P<0·05) when the rats were treated with recFSH. EDS alone did not affect testicular testosterone but, when combined with recFSH, it totally abolished the stimulatory effect of FSH on testosterone. Testicular binding of ¹²⁵I-labelled iodo human chorionic gonadotrophin (hCG) and ¹²⁵I-labelled iodo recFSH was increased 2·5- and 2·1-fold respectively with recFSH treatment (P<0·01). EDS, either alone or with FSH, abolished specific testicular hCG binding (P<0·01), but had no effect on that of recFSH. However, FSH increased its own receptors only in animals not treated with EDS.

Histological analysis of the testes revealed that the diameters of the seminiferous tubules increased from 115 ± 6·1 to 160 ± 7·2 μm (P<0·05) with recFSH, and a comparable increase was observed when EDS treatment preceded that of recFSH (143 ± 1·5 μm, P<0·05 vs. controls). Quantification of the spermatogenic cells indicated that recFSH supported the progression of spermatogenesis, as shown by increased number of meiotic and haploid spermatogenic cells (P<0·05). In all EDS-treated animals, spermatogenesis was severely disturbed and only a few spermatids were seen.

In conclusion: (1) these results further support the suggestion that FSH has indirect stimulatory effects on Leydig cell function, (2) the completion of meiosis and spermiogenesis are supported by FSH, the effect of which is enhanced by the presence of Leydig cells, suggesting its dependence on androgens, and (3) we show for the first time that FSH is able to stimulate its own receptors only in the presence of Leydig cell-derived factors, probably androgens.

Journal of Endocrinology (1994) 141, 449–457

Abstract

The prolactin receptor (PRLR) is a member of the cytokine/prolactin/GH receptor family, and it is widely expressed in various mammalian tissues. Expression of the two different forms of PRLR, differing in the length of their cytoplasmic domains, was studied in rat gonads during fetal and postnatal development. The two forms of PRLR mRNA were analyzed by reverse transcription (RT)-PCR using primer pairs specific for the different forms. The specificity of the cDNA species generated by RT-PCR was verified by Southern hybridization using nested ³²P-labeled oligonucleotides. The results indicated that both forms of PRLR mRNA are expressed in the rat testis and ovary, which is in agreement with previous reports. The onset of expression of the two PRLR forms occurs on day 14·5 of fetal life in rat testis. In the ovary, the long form of PRLR mRNA appears 1 day before the short form, i.e. these forms begin to be expressed on fetal days 14·5 and 15·5 respectively. In situ hybridization with antisense cRNA probes specific to each form of the PRLR mRNAs demonstrated specific hybridization of both forms, localized in Leydig cells from day 18·5 of fetal life and at the postnatal ages studied. Compared with our previous findings concerning the ontogeny of LH receptor gene expression, PRLR gene expression starts earlier in development and exhibits no sexual dimorphism. The presence of two forms of PRLR mRNA in the fetal gonads suggest that they might play differential roles in gonadal development and function.

Journal of Endocrinology (1995) 147, 497–505

ABSTRACT

Plasminogen activator (PA) is secreted cyclically (in stages VII and VIII) by rat seminiferous tubules. To investigate whether this can be maintained and influenced in vitro, tubule segments from stages VI and VIII of the epithelial cycle were cultured for 3 days in chemically defined medium supplemented with testosterone, FSH, or a combination of testosterone, FSH, insulin and retinoic acid (4F).

Morphological and flow cytometric analyses of stage VI tubules suggested a roughly normal differentiation to stage VIII. They developed an increased PA secretion on day 3 of culture. Stage VIII tubules, however, did not develop all the characteristics of stage XII. Step 8 spermatids did not elongate and step 19 spermatids failed to develop into spermatozoa. Secretion of PA on day 3 was not significantly different to that on day 1. The 4F combination very significantly stimulated PA secretion in both stages, but FSH alone was effective only in stage VIII. Most of the secreted PA had a molecular weight of 43 000 in both stages, suggesting that it is of urokinase type.

The results suggest that stage VI is more able to differentiate in vitro for 3 days than stage VIII; the cyclic secretion pattern of PA was partially maintained in tubule segments from stage VI. Follicle-stimulating hormone had an effect on PA secretion only in stage VIII, whereas the 4F combination was stimulatory in both stages. The retinoic acid in this combination may be of importance in the regulation of PA secretion by seminiferous tubules.

J. Endocr. (1986) 108, 417–422

Abstract

Stage-specific expression of the FSH receptor (FSHR) gene in the rat seminiferous epithelium was studied. Using transillumination-assisted microdissection for sample preparation and Northern hybridization for analysis of total RNA, we first reassessed the stage specificity of the FSHR gene expression in the adult rat testis. Sixfold higher FSHR mRNA levels were found in stages XIII–I compared with stage VI of the seminiferous epithelial cycle, which had the lowest signal level (P<0·01). The other stages had intermediate signal levels. In situ hybridization showed distribution of grains which confirmed the data obtained by Northern analysis. Prepubertal stage-specific FSHR gene expression was studied using in situ hybridization. Stage specificity could first be demonstrated at the age of 16 days when the average grain counts in stages I–IV were threefold higher than in stages VI–VII (P<0·01). The present data are in agreement with earlier findings on stage-specific FSH binding and FSHR gene expression using both microdissected and stage-synchronized seminiferous tubules. The onset of stage-specific FSHR gene expression is concomitant with maturation of the Sertoli cell population and completion of the first generation of spermatocytes. This supports the hypothesis that spermatogonia and spermatocytes may be involved in the regulation of FSHR gene expression.

Journal of Endocrinology (1996) 151, 29–35

Abstract

We studied the cellular distribution of inhibin α, β_A and β_B mRNAs in the normal human ovary and in polycystic ovarian syndrome (PCOS) by in situ hybridization. Our results show that human granulosa cells express inhibin α, β_A and β_B subunit mRNAs, and theca cells express inhibin α and β_A subunit mRNAs. The co-localization of α and β_A mRNAs in theca cells supports the hypothesis that inhibin also has an autocrine function in these cells. We did not detect any inhibin subunit mRNA in the granulosa cells of atretic follicles, while theca cells also expressed α subunit mRNA in those follicles. The present findings suggest that the expression of inhibin subunits is regulated differently in human follicular granulosa and theca cells. It has been speculated that inhibin may be involved in the development of PCOS. Our results show that the cellular localization of inhibin subunit mRNAs is not disturbed in PCOS ovaries.

Journal of Endocrinology (1994) 143, 127–137