The epididymis is the site of sperm maturation and storage. 5alpha-Reductases (types 1 and 2) are key enzymes in this tissue because they convert testosterone to dihydrotestosterone (DHT), the main androgen regulating epididymal functions. Examining the consequences of inhibiting DHT formation is likely to provide important information regarding the regulation of epididymal functions, yet few inhibitor studies have focused on this tissue. To understand better DHT-mediated regulation of epididymal gene expression, we employed a dual 5alpha-reductase inhibitor and cDNA microarrays to examine the effects of 5alpha-reductase inhibition on gene expression in the initial segment, caput, corpus, and cauda epididymidis. Inhibition of epididymal 5alpha-reductase activity by PNU157706 was confirmed by in vitro enzyme assays. Rats were treated with 0, 0.1, 1.0 or 10 mg/kg per day PNU157706 for 28 days. The weights of DHT-dependent tissues, including the epididymis, were decreased following treatment. The effect of treatment on gene expression was dose-dependent and highly segment-specific. The initial segment responded uniquely in that a similar number of genes increased and decreased in expression compared with the other segments where the majority of affected genes decreased in expression. Some of the more dramatically affected genes were involved in signal transduction as well as fatty acid and lipid metabolism, regulation of ion and fluid transport, luminal acidification, oxidative defense and protein processing and degradation. These are essential processes contributing to the formation of an optimal luminal microenvironment required for proper sperm maturation. These results provide a novel insight into the DHT-dependent mechanisms that control epididymal functions.
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NA Henderson, GM Cooke, and B Robaire
D. S. Keeney, R. L. Sprando, B. Robaire, B. R. Zirkin, and L. L. Ewing
The purpose of this study was to determine whether Leydig cell volume and function could recover fully from long-term LH deprivation upon restoration of endogenous LH secretion, and whether the restoration of LH would elicit a mitogenic response, i.e. stimulate Leydig cell proliferation or affect Leydig cell number per testis. LH secretion was inhibited by treating adult rats with testosterone and oestradiol-filled (TO) silicone elastomer implants (16 weeks), and was restored by removing the implants. Changes in serum concentrations of LH and FSH, LH-stimulated testosterone secretion by testes perfused in vitro, Leydig cell volume and number per testis, average Leydig cell volume and Leydig cell [3H]thymidine incorporation were measured at weekly intervals following implant removal.
The TO implants inhibited (P < 0·01) LH secretion, but serum concentrations of FSH were not significantly different (P > 0·10) from control values. After implant removal, serum LH returned to control values within 1 week, whereas serum FSH increased twofold (P < 0·01) and returned to control values at 4 weeks. LH-stimulated in-vitro testosterone secretion was inhibited by more than 99% in TO-implanted rats, but increased (P < 0·01) to 80% of control values by 8 weeks after implant removal. The total volume of Leydig cells per testis and the volume of an average Leydig cell were 14 and 19% of control values respectively, after 16 weeks of TO implantation (P < 0·01), but returned to 83 and 86% of controls (P > 0·10) respectively, by 6 weeks after implant removal.
Leydig cell proliferation ([3H]thymidine labelling index) was low (< 0·1%) in both control and TO-implanted rats, increased (P < 0·01) fivefold from 1 to 4 weeks after implant removal and then declined to control values at 6 weeks. The increase in Leydig cell [3H]thymidine incorporation was mimicked by treating TO-implanted rats with exogenous LH, but not FSH.
Leydig cells were identified in both the interstitium and the lamina propria of the seminiferous epithelium. The proportion of Leydig cell nuclei in the lamina propria was 30-fold greater (P < 0·01) at 1 and 3 weeks after implant removal (3%) compared with that for control and TO-implanted rats (0·1%). Total Leydig cell number per testis was marginally but not significantly (P = 0·06) decreased in rats treated with TO implants for 16 weeks when compared with controls (18·4±2·2 vs 25·4±1·2 × 106). Three weeks after implant removal, the numbers of Leydig cells per testis were identical (26·8±2·8 × 106) to those in control animals. These results not only demonstrate dramatic morphogenic effects of LH on mature rat Leydig cells, but also suggest that endogenous LH might be mitogenic at least to a subpopulation of Leydig cells.
Journal of Endocrinology (1990) 127,47–58
P. M. Grosser, G. F. McCarthy, B. Robaire, R. Farookhi, and J. R. Brawer
The patterns of plasma LH, FSH and prolactin concentrations were investigated in rats with a polycystic ovary condition (PCO). The condition was induced by treatment with oestradiol valerate 9 weeks before blood sampling. Serial blood samples were taken at 10-min intervals for 4 h from ten rats with PCO. All samples were assayed for LH, those from five animals for FSH and those from the remaining five animals for prolactin. In addition, five control animals with normal oestrous cycles were sampled during oestrus and the samples assayed for LH. Mean concentrations of LH, FSH and prolactin in rats with PCO were 140 ng/l, 76 μg/l and 7·6 μg/l respectively. All three hormones exhibited an episodic pattern. The mean peak amplitudes of LH, FSH and prolactin were 120 ng/l, 25 μg/l and 3·5 μg/l respectively. All three hormones exhibited a similar mean frequency of four or five episodes per 4 h. The LH and FSH patterns were closely synchronized; nearly all FSH peaks coincided with LH peaks. The prolactin pattern did not, however, correlate with that of the gonadotrophins. Despite the persistent oestrous condition of the animals with PCO, it was clear that their pattern of LH did not resemble that of cyclic animals in normal oestrus; in the normally cyclic animals in oestrus the pulse period was nearly twice as long and the pulse amplitude was more than sixfold greater than those in animals with PCO. We conclude that the unique episodic patterns of gonadotrophins are more important than mean blood concentrations of these hormones in establishing and maintaining the polycystic ovary syndrome.
J. Endocr. (1987) 114, 33–39