Role of ghrelin on testosterone secretion and the mRNA expression of androgen receptors in adult rat testis

ABSTRACT Iron is required for the normal development of germ cells during spermatogenesis. Because these cells have no direct access to systemic iron, there exists a shuttle system involving production and secretion of the iron-transporting protein transferrin by the Sertoli cells. Previous reports using cultures of immature Sertoli cells exposed to adult germ cells, or in vivo studies involving germ cell-depleted adult rat testes, concluded that production of transferrin by Sertoli cells is modulated by germ cell complement. In the present study we have used in situ hybridisation with cRNA probes directed against the 5′ and 3′ ends of transferrin mRNA to examine the pattern of expression of transferrin in the immature and adult rat testis. Adult rats were treated with ethane dimethane sulphonate or methoxyacetic acid (MAA) to manipulate their testosterone levels or germ cell complement respectively. Initial findings obtained using the 3′ probe showed a decrease in transferrin mRNA associated with round spermatid depletion. However, these data were not confirmed by in situ hybridisation when the 5′ probe was used. The specificity of the probes was examined using Northern blotting and the 3′ probe was found to hybridise to the germ cell transcript for hemiferrin even under conditions of high stringency. Examination of immature and pubertal rat testes by in situ hybridisation using the 5′ transferrin-specific probe found that as early as 14 days of age the level of expression of transferrin mRNA was clearly different between tubules, and the mRNA appeared to be expressed in Leydig cells on and after day 31. In the adult rat testis, maximal expression of transferrin mRNA was found at stages VIII-XIV, calling into question the interpretation of the results of some previous studies showing expression of transferrin mRNA at all stages of the spermatogenic cycle. This stage-specific pattern of expression was not altered by acute germ cell depletion using MAA. However, Northern blot analysis showed a statistically significant increase in transferrin mRNA expression at 7 days after MAA treatment when pachytene spermatocytes were depleted from tubules at all stages of the spermatogenic cycle at which transferrin is normally expressed. In conclusion, we found that transferrin mRNA expression was not modulated by round spermatids as has been reported previously but that meiotic germ cells may influence expression of transferrin at specific stages of the spermatogenic cycle.

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The expression and regulation of Bcl-2-related ovarian killer (Bok) mRNA in the developing and adult rat testis

Acta Endocrinologica ◽

10.1530/eje.0.1450771 ◽

2001 ◽

pp. 771-778 ◽

Cited By ~ 11

Author(s):

JS Suominen ◽

W Yan ◽

J Toppari ◽

A Kaipia

Keyword(s):

Mrna Expression ◽

Northern Hybridization ◽

Seminiferous Tubules ◽

Testicular Development ◽

Rat Testis ◽

Adult Rat ◽

Before And After ◽

Hybridization Intensity ◽

Pachytene Spermatocytes

OBJECTIVE: To study the role of Bcl-2-related ovarian killer (Bok) in the regulation of apoptosis in the testis of developing and adult rat. METHODS: Bok mRNA expression was analyzed by Northern hybridization before and after culturing rat seminiferous tubules in vitro. Seminiferous tubules were cultured with different hormones and growth factors. Changes in the expression level of Bok mRNA during testicular development was analyzed by Northern hybridization. Localization of Bok mRNA was verified by in situ hybridization. RESULTS: Bok mRNA was highly expressed in the rat testis, varying during development. Highest expression levels were found in immature rats. Highest hybridization intensity appeared to be in spermatogonia, pachytene spermatocytes and Sertoli cells. Treatment with FSH was able to inhibit spontaneous increase of Bok mRNA expression that occurred in the defined stages of the rat seminiferous epithelium. CONCLUSIONS: FSH protects germ cells from apoptosis and this protective effect may at least partly be due to the inhibition of Bok gene expression. The amount of apoptosis varies during testicular development and highest expression of Bok mRNA occurs at the time of apoptosis, suggesting a possible role for Bok in its regulation.

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Age- and cell-related gene expression of aromatase and estrogen receptors in the rat testis

Journal of Molecular Endocrinology ◽

10.1677/jme-10-0041 ◽

2010 ◽

Vol 45 (3) ◽

pp. 147-159 ◽

Cited By ~ 36

Author(s):

C Bois ◽

C Delalande ◽

M Nurmio ◽

M Parvinen ◽

L Zanatta ◽

...

Keyword(s):

Gene Expression ◽

Estrogen Receptors ◽

Expression Patterns ◽

Mrna Levels ◽

Paracrine Factors ◽

Rat Testis ◽

Adult Rat ◽

Pachytene Spermatocytes ◽

Nuclear Estrogen Receptors

Spermatogenesis is a complex and coordinated process leading to the formation of spermatozoa. This event, which is under the control of numerous endocrine and paracrine factors, seems to also be controlled by estrogens which exert their effects via nuclear estrogen receptors (ESRs) ESR1 and ESR2. Estrogens are synthesized by aromatase which is biologically expressed in the rat testis. The objective of our study was to clarify the gene expression patterns of aromatase and ESRs according to age and in the two compartments of the adult rat testis. In the adult, transcripts of aromatase vary according to the germ cell type and to the stages of seminiferous epithelium, a maximum being observed at stage I. The ESR1 gene is highly expressed in the adult testis and in stages from VIIc–d to XIV. Moreover, both ESR mRNA levels are higher in purified round spermatids than in pachytene spermatocytes, suggesting a putative role of estrogens in the haploid steps of spermatogenesis. The variability of the results in the expression of both ESRs led us to explore the putative presence of variants in the rat testis. Concerning ESR1, we have shown the presence of the full-length form and of one isoform with exon 4 deleted. For ESR2, besides the wild type, three isoforms were observed: one with exon 3 deleted, another with an insertion of 54 nucleotides, and the last one with both modifications. Therefore, the stage-regulated expression of aromatase and ESR1 genes in the rat testis suggests a likely role of estrogens in spermatogenesis.

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Molecular mechanisms of leptin action in adult rat testis: potential targets for leptin-induced inhibition of steroidogenesis and pattern of leptin receptor messenger ribonucleic acid expression

Journal of Endocrinology ◽

10.1677/joe.0.1700413 ◽

2001 ◽

Vol 170 (2) ◽

pp. 413-423 ◽

Cited By ~ 93

Author(s):

M Tena-Sempere ◽

PR Manna ◽

FP Zhang ◽

L Pinilla ◽

LC Gonzalez ◽

...

Keyword(s):

Molecular Mechanisms ◽

Leptin Receptor ◽

Cellular Distribution ◽

R Gene ◽

Expression Levels ◽

Rat Testis ◽

Adult Rat ◽

Testosterone Secretion ◽

Cellular Expression

Leptin, the product of the ob gene, is a pivotal signal in the regulation of neuroendocrine function and fertility. Although much of the action of leptin in the control of the reproductive axis is exerted at the hypothalamic level, some direct effects of leptin on male and female gonads have also been reported. Indeed, recent evidence demonstrated that leptin is able to inhibit testosterone secretion at the testicular level. However, the molecular mechanisms behind this effect remain unclear. The focus of this study was twofold: (1) to identify potential targets for leptin-induced inhibition of steroidogenesis, and (2) to characterize in detail the pattern of expression and cellular distribution of leptin receptor (Ob-R) mRNA in adult rat testis. In pursuit of the first goal, slices of testicular tissue from adult rats were incubated with increasing concentrations of recombinant leptin (10(-9)--10(-7 )M) in the presence of human chorionic gonadotropin (hCG; 10 IU/ml). In this setting, testosterone secretion in vitro was monitored, and expression levels of mRNAs encoding steroidogenic factor 1 (SF-1), steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450 scc) and 17 beta-hydroxysteroid dehydrogenase type III (17 beta-HSD) were assessed by Northern hybridization. In pursuit of the second goal, the pattern of cellular expression of the Ob-R gene in adult rat testis was evaluated by in situ hybridization using a riboprobe complementary to all Ob-R isoforms. In addition, testicular expression levels of the different Ob-R isoforms, previously identified in the hypothalamus, were analyzed by means of semi-quantitative RT-PCR. In keeping with our previous data, recombinant leptin significantly inhibited hCG-stimulated testosterone secretion. In this context, leptin, in a dose-dependent manner, was able to co-ordinately decrease the hCG-stimulated expression levels of SF-1, StAR and P450 scc mRNAs, but it did not affect those of 17 beta-HSD type III. In situ hybridization analysis showed a scattered pattern of cellular expression of the Ob-R gene within the adult rat testis, including Leydig and Sertoli cells. In addition, assessment of the pattern of expression of Ob-R subtypes revealed that the long Ob-Rb isoform was abundantly expressed in adult rat testis. However, variable levels of expression of Ob-Ra, Ob-Re, and Ob-Rf mRNAs were also detected, whereas those of the Ob-Rc variant were nearly negligible. In conclusion, our results indicate that decreased expression of mRNAs encoding several up-stream elements in the steroidogenic pathway may contribute, at least partially, to leptin-induced inhibition of testicular steroidogenesis. In addition, our data on the pattern of testicular expression of Ob-R isoforms and cellular distribution of Ob-R mRNA may help to further elucidate the molecular mechanisms of leptin action in rat testis.

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