Maddineni Sreenivasa R, Ocón-Grove Olga M, Krzysik-Walker Susan M, Hendricks Gilbert L, Ramachandran Ramesh
Department of Poultry Science, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Reproduction. 2008 Feb;135(2):267-74. doi: 10.1530/REP-07-0369.
Gonadotropin-inhibitory hormone (GnIH), an RFamide peptide, has been found to inhibit pituitary LH secretion in avian and mammalian species. The gene encoding a putative receptor for GnIH (GnIHR) was recently identified in the chicken and Japanese quail brain and pituitary gland. GnIHR appears to be a seven-transmembrane protein belonging to a family of G-protein-coupled receptors. In the present study, we have characterized the expression of GnIHR mRNA in the chicken ovary and demonstrate that GnIHR may exert an inhibitory effect on ovarian follicular development. By RT-PCR, we detected GnIHR mRNA in the chicken testis and in the ovary, specifically both thecal and granulosa cell layers. Real-time quantitative PCR analysis revealed greater GnIHR mRNA quantity in theca cells of prehierarchial follicles compared with that of preovulatory follicles. GnIHR mRNA quantity was significantly decreased in sexually mature chicken ovaries versus ovaries of sexually immature chickens. Estradiol (E(2)) and/or progesterone (P(4)) treatment of sexually immature chickens significantly decreased ovarian GnIHR mRNA abundance. Treatment of prehierarchial follicular granulosa cells in vitro with chicken GnIH peptide significantly decreased basal but not FSH-stimulated cellular viability. Collectively, our results indicate that the ovarian GnIHR is likely to be involved in ovarian follicular development. A decrease in ovarian GnIHR mRNA abundance due to sexual maturation or by E(2) and/or P(4) treatment would implicate an inhibitory role for GnIHR in ovarian follicular development. Furthermore, GnIH may affect follicular maturation by decreasing the viability of prehierarchial follicular granulosa cells through binding to GnIHR.
促性腺激素抑制激素（GnIH）是一种RFamide肽，已发现在鸟类和哺乳动物中可抑制垂体促黄体生成素（LH）的分泌。最近在鸡和日本鹌鹑的脑及垂体中鉴定出了编码GnIH假定受体（GnIHR）的基因。GnIHR似乎是一种属于G蛋白偶联受体家族的七跨膜蛋白。在本研究中，我们对鸡卵巢中GnIHR mRNA的表达进行了表征，并证明GnIHR可能对卵泡发育产生抑制作用。通过逆转录聚合酶链反应（RT-PCR），我们在鸡睾丸和卵巢中检测到了GnIHR mRNA，特别是在卵泡膜细胞层和颗粒细胞层。实时定量PCR分析显示，与排卵前卵泡相比，等级前卵泡的卵泡膜细胞中GnIHR mRNA的量更多。性成熟鸡的卵巢中GnIHR mRNA的量明显低于性未成熟鸡的卵巢。用雌二醇（E2）和/或孕酮（P4）处理性未成熟鸡，可显著降低卵巢GnIHR mRNA的丰度。用鸡GnIH肽体外处理等级前卵泡颗粒细胞，可显著降低基础细胞活力，但对促卵泡激素（FSH）刺激的细胞活力无影响。总体而言，我们的结果表明卵巢GnIHR可能参与卵泡发育。由于性成熟或E2和/或P4处理导致卵巢GnIHR mRNA丰度降低，这表明GnIHR在卵泡发育中起抑制作用。此外，GnIH可能通过与GnIHR结合降低等级前卵泡颗粒细胞的活力，从而影响卵泡成熟。
