Scuola di Scienze mediche veterinarie, Università di Camerino, 62024 Matelica, Italy.
J Endocrinol. 2010 Dec;207(3):289-300. doi: 10.1677/JOE-10-0109. Epub 2010 Sep 29.
The expression of type I GNRH receptor (GNRHR-I) and the direct role of GNRH-I on corpora lutea (CL) function were studied in the pseudopregnant rabbit model. Immunohistochemistry evidenced GNRHR-I and GNRH-I in luteal cells at early (day 4 pseudopregnancy)-, mid (day 9)-, and late (day 13)-luteal stages. Real-time RT-PCR and western blotting revealed GNRHR-I mRNA and protein at the three luteal stages. Buserelin in vivo treatment at days 9 and 13 decreased plasma progesterone levels for 48 and 24 h respectively. In in vitro cultured CL, buserelin reduced progesterone secretion, increased prostaglandin F(2α) (PGF(2α)) secretion and cyclo-oxygenase-2 (COX-2) and nitric oxide synthase (NOS) activities at days 9 and 13, and decreased PGE₂ at day 13. Co-incubation with antagonists for GNRH-I (antide), inositol 1,4,5-trisphosphate (IP₃, 2-amino-ethoxydiphenylborate), and diacylglycerol (DAG, 1-hexadecyl-2-acetyl glycerol) or inhibitors for phospholipase C (PLC, compound 48/80), and protein kinase C (PKC, staurosporine) counteracted the buserelin effects. Buserelin co-incubated with COX inhibitor (acetylsalicylic acid) increased progesterone and decreased PGF(2α) and NOS activity at days 9 and 13, whereas co-incubation with NOS inhibitor (N-nitro-l-arginine methyl ester) increased progesterone at the same luteal stages. These results suggest that GNRHR-I is constitutively expressed in rabbit CL independently of luteal stage, whereas GNRH-I down-regulates directly CL progesterone production via PGF(2α) at mid- and late-luteal stages of pseudopregnancy, utilizing its cognate type I receptor with a post-receptorial mechanism that involves PLC, IP₃, DAG, PKC, COX-2, and NOS.
在假孕兔模型中研究了 I 型促性腺激素释放激素受体 (GNRHR-I) 的表达及其对黄体 (CL) 功能的直接作用。免疫组织化学证据表明，GNRHR-I 和 GNRH-I 在黄体细胞中表达，分别在早黄体期（假孕第 4 天）、中黄体期（假孕第 9 天）和晚黄体期（假孕第 13 天）。实时 RT-PCR 和 Western blot 显示在三个黄体期均有 GNRHR-I mRNA 和蛋白表达。在体内用布舍瑞林处理 9 天和 13 天分别导致血浆孕酮水平下降 48 和 24 小时。在体外培养的 CL 中，布舍瑞林降低了孕酮分泌，增加了前列腺素 F(2α) (PGF(2α))分泌和环氧化酶-2 (COX-2) 和一氧化氮合酶 (NOS) 在第 9 天和第 13 天的活性，并降低了第 13 天的 PGE₂。用 GNRH-I 拮抗剂（antide）、肌醇 1,4,5-三磷酸 (IP₃、2-氨基乙氧基二苯硼酸盐)和二酰基甘油 (DAG、1-十六烷基-2-乙酰甘油)共孵育或用 PLC 抑制剂（化合物 48/80）和蛋白激酶 C (PKC、staurosporine)抑制剂，拮抗布舍瑞林的作用。布舍瑞林与 COX 抑制剂（乙酰水杨酸）共孵育增加了第 9 天和第 13 天的孕酮，降低了 PGF(2α)和 NOS 活性，而与 NOS 抑制剂（N-硝基-L-精氨酸甲酯）共孵育增加了同一黄体阶段的孕酮。这些结果表明，GNRHR-I 在兔 CL 中组成性表达，与黄体阶段无关，而 GNRH-I 通过中黄体期和晚期黄体期的 PGF(2α)下调直接 CL 孕酮产生，利用其同源 I 型受体，通过 PLC、IP₃、DAG、PKC、COX-2 和 NOS 的受体后机制。
