Low levels of Gαs and Ric8b in testicular sertoli cells may underlie restricted FSH action during infancy in primates.

FSH acts via testicular Sertoli cells (Sc) bearing FSH receptor (FSH-R) for regulating male fertility. Despite an adult-like FSH milieu in infant boys and monkeys, spermatogenesis is not initiated until the onset of puberty. We used infant and pubertal monkey Sc to reveal the molecular basis underlying developmental differences of FSH-R signaling in them. Unlike pubertal Sc, increasing doses of FSH failed to augment cAMP production by infant Sc. The expression of Gαs subunit and Ric8b, which collectively activate adenylyl cyclase (AC) for augmenting cAMP production and gene transcription, were significantly low in infant Sc. However, forskolin, which acts directly on AC bypassing FSH-R, augmented cAMP production and gene transcription uniformly in both infant and pubertal Sc. FSH-induced Gαs mRNA expression was higher in pubertal Sc. However, Gαi-2 expression was down-regulated by FSH in pubertal Sc, unlike infant Sc. FSH failed, but forskolin or 8-Bromoadenosine 3',5'-cyclic monophosphate treatment to infant Sc significantly augmented the expression of transferrin, androgen binding protein, inhibin-ß-B, stem cell factor, and glial-derived neurotropic factor, which are usually up-regulated by FSH in pubertal Sc during spermatogenic onset. This suggested that lack of FSH mediated down-regulation of Gαi-2 expression and limited expression of Gαs subunit as well as Ric8b may underlie limited FSH responsiveness of Sc during infancy. This study also divulged that intracellular signaling events downstream of FSH-R are in place and can be activated exogenously in infant Sc. Additionally, this information may help in the proper diagnosis and treatment of infertile individuals having abnormal G protein-coupled FSH-R.

Follicle-stimulating hormone-independent functions of primate Sertoli cells: potential implications in the diagnosis and management of male infertility.

CONTEXT: FSH is known to augment the production of essential germ cell (Gc) survival factors, lactate and estradiol, by Sertoli cells (Sc) of 18-d-old pubertal rats. However, the failure of gonadotropin and androgen treatment to initiate spermatogenesis in testis of some infertile men bearing Sc and Gc is intriguing. The role of FSH in regulation of lactate and estradiol production by primate Sc is currently unknown. OBJECTIVE: The objective of the study was to determine the role of FSH in regulating lactate and estradiol production by primate Sc. METHODS: Gc differentiation was initiated in male juvenile rhesus monkeys by pulsatile administration of GnRH for 4-5 wk. Sc from these pseudopubertal monkeys and pubertal rats were cultured. Production of lactate and estradiol in response to FSH and 8-bromoadenosine-cAMP was evaluated. Inhibin-betaB expression, cAMP production, and cell proliferation were also assayed. RESULTS: Unlike Sc from pubertal rats, Sc from pseudopubertal monkeys constitutively aromatized testosterone to estradiol and produced large amounts of lactate without FSH stimulation. Increasing doses of recombinant monkey FSH or 8-bromoadenosine-cAMP failed to augment lactate production, although they significantly augmented proliferation of Sc. Production of cAMP and expression of inhibin-betaB mRNA were also remarkably augmented by recombinant monkey FSH. CONCLUSIONS: These results suggest that lactate and estradiol production by monkey Sc is not governed by FSH, as previously thought based on studies of rat Sc. Thus, in a clinical situation, assessment of such gonadotropin-independent functions of Sc may be obligatory for the diagnosis and management of certain forms of idiopathic male infertility.