Kakar S S, Grantham K, Musgrove L C, Devor D, Sellers J C, Neill J D
Department of Physiology and Biophysics, University of Alabama at Birmingham, 35294, USA.
Mol Cell Endocrinol. 1994 May;101(1-2):151-7. doi: 10.1016/0303-7207(94)90229-1.
The binding of gonadotropin-releasing hormone (GnRH) to its receptor in the anterior pituitary gland is the key molecular interaction regulating the reproductive process of mammals. Here, we report the isolation of a cDNA representing this receptor from rat anterior pituitary and the regulation of expression of its mRNA. The rat GnRH receptor cDNA was composed of 2909 nucleotides and encoded a protein containing 327 amino acids having a seven transmembrane topology. Northern blot analysis on RNA from rat pituitary, ovary and testis showed four different transcripts (5.0, 4.5, 2.5 and 1.3 kb) of which the 5.0 kb form was most abundant. The levels of expression of the transcripts were found to be highest in the pituitary followed by the ovary and the testis (about 40% and 5% compared to pituitary, respectively). Using the more sensitive reverse transcriptase/PCR technique, we also detected GnRH receptor mRNA in the adrenal and the hypothalamus. Measurement of pituitary GnRH receptor mRNA levels (the 5.0 kb form) during the estrous cycle showed the lowest levels at estrus (1.0-fold), a 2.2 +/- 0.57 (mean +/- SEM) -fold increase at diestrus I, a 3.5 +/- 0.41-fold increase at diestrus II, a 2.6 +/- 0.34-fold increase on the morning of proestrus, and a 1.9 +/- 0.25-fold on the afternoon of proestrus. Removal of the ovaries led to a 2.7 +/- 0.29-fold increase in GnRH receptor mRNA levels in the pituitary gland; treatment of ovariectomized rats with estrogen resulted in a significant decrease in GnRH receptor mRNA levels. Our studies demonstrate ovarian regulation of GnRH receptor mRNA expression in the anterior pituitary gland.
促性腺激素释放激素（GnRH）与其在前脑垂体中的受体结合是调节哺乳动物生殖过程的关键分子相互作用。在此，我们报告了从大鼠前脑垂体中分离出代表该受体的cDNA及其mRNA表达的调节。大鼠GnRH受体cDNA由2909个核苷酸组成，编码一种含有327个氨基酸的蛋白质，具有七跨膜拓扑结构。对大鼠垂体、卵巢和睾丸的RNA进行Northern印迹分析，显示出四种不同的转录本（5.0、4.5、2.5和1.3 kb），其中5.0 kb的形式最为丰富。发现这些转录本的表达水平在垂体中最高，其次是卵巢和睾丸（分别约为垂体的40%和5%）。使用更敏感的逆转录酶/PCR技术，我们还在肾上腺和下丘脑中检测到了GnRH受体mRNA。在发情周期中测量垂体GnRH受体mRNA水平（5.0 kb形式），结果显示发情期水平最低（1.0倍），动情间期I增加2.2±0.57（平均值±标准误）倍，动情间期II增加3.5±0.41倍，发情前期早晨增加2.6±0.34倍，发情前期下午增加1.9±0.25倍。摘除卵巢导致垂体中GnRH受体mRNA水平增加2.7±0.29倍；用雌激素处理去卵巢大鼠导致GnRH受体mRNA水平显著降低。我们的研究证明了卵巢对前脑垂体中GnRH受体mRNA表达的调节作用。
