IRTA, Institut de Ciències del Mar, Barcelona, Spain.
Biol Reprod. 2012 Aug 9;87(2):35. doi: 10.1095/biolreprod.112.100784. Print 2012 Aug.
The endocrine pathways controlling vertebrate spermatogenesis are well established in mammals where the pituitary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) exclusively activate the FSH receptor (FSHR) in Sertoli cells and the LH/choriogonadotropin receptor (LHCGR) in Leydig cells, respectively. In some teleosts, however, it has been shown that Lh can cross-activate the Fshra ortholog, and that Leydig cells coexpress the Lhcgrba and Fshra paralogs, thus mediating the androgenic function of Fsh in the testis. Here, we investigated whether these proposed mechanisms are conserved in an evolutionary advanced pleuronectiform teleost, the Senegalese sole (Solea senegalensis). Transactivation assays using sole Fshra- and Lhcgrba-expressing cells and homologous single-chain recombinant gonadotropins (rFsh and rLh) showed that rFsh exclusively activated Fshra, whereas rLh stimulated both Lhcgrba and Fshra. The latter cross-activation of Fshra by rLh occurred with an EC(50) 4-fold higher than for rFsh. Both recombinant gonadotropins elicited a significant androgen release response in vitro and in vivo, which was blocked by protein kinase A (PKA) and 3beta-hydroxysteroid dehydrogenase inhibitors, suggesting that activation of steroidogenesis through the cAMP/PKA pathway is the major route for both Lh- and Fsh-stimulated androgen secretion. Combined in situ hybridization and immunocytochemistry using cell-specific molecular markers and antibodies specifically raised against sole Fshra and Lhcgrba demonstrated that both receptors are expressed in Leydig cells, whereas Sertoli cells only express Fshra. These data suggest that Fsh-mediated androgen production through the activation of cognate receptors in Leydig cells is a conserved pathway in Senegalese sole.
控制脊椎动物精子发生的内分泌途径在哺乳动物中已经得到很好的建立，其中垂体促性腺激素卵泡刺激素 (FSH) 和黄体生成素 (LH) 专门激活 Sertoli 细胞中的 FSH 受体 (FSHR) 和黄体生成素/绒毛膜促性腺激素受体 (LHCGR) 在 Leydig 细胞中。然而，在一些鱼类中已经表明，Lh 可以交叉激活 Fshra 同源物，并且 Leydig 细胞共同表达 Lhcgrba 和 Fshra 旁系同源物，从而介导 Fsh 在睾丸中的雄激素功能。在这里，我们研究了这些提出的机制是否在进化先进的 Pleuronectiform 鱼类，塞内加尔 sole（Solea senegalensis）中保守。使用 sole Fshra 和 Lhcgrba 表达细胞和同源单链重组促性腺激素 (rFsh 和 rLh) 的转激活测定表明，rFsh 专门激活 Fshra，而 rLh 刺激 Lhcgrba 和 Fshra。rLh 对 Fshra 的这种交叉激活的 EC(50) 比 rFsh 高 4 倍。两种重组促性腺激素在体外和体内均引起显著的雄激素释放反应，该反应被蛋白激酶 A (PKA) 和 3β-羟甾脱氢酶抑制剂阻断，表明通过 cAMP/PKA 途径激活类固醇生成是 Lh 和 Fsh 刺激雄激素分泌的主要途径。使用细胞特异性分子标记物和专门针对 sole Fshra 和 Lhcgrba 产生的抗体进行的原位杂交和免疫细胞化学组合表明，两种受体均在 Leydig 细胞中表达，而 Sertoli 细胞仅表达 Fshra。这些数据表明，通过在 Leydig 细胞中激活同源受体，Fsh 介导的雄激素产生是塞内加尔 sole 中的一种保守途径。
