MECHANISM OF ACTION OF GONADOTROPINS IN THE TESTIS

该项目的长期目标是描述这些机制的特征， 决定睾丸间质细胞产生睾丸激素的能力。 我们 通过研究这些活动之间的关系， 类固醇生物合成酶，以最大的睾酮生产在两个 Leydig细胞的功能不同群体， 促性腺激素处理的大鼠。 本研究的具体目标是 旨在评估类固醇生成途径中可能 在决定睾丸间质细胞产生睾酮的能力方面起决定性作用 以及阐明促黄体生成激素（LH） 和cAMP增加或减少最大睾酮产生 这取决于它们的施用方式。 具体来说，我们将 确定：1）胆固醇侧链裂解的活性是否 酶（P-450 SCC）在两个Leydig细胞群体中不同， LH的长期体内治疗是否增加了 使用Leydig的匀浆或富集的线粒体级分的P-450 SCC 通过Metrizamide梯度将细胞分成两个群体 2）催乳素在调节中的作用 大鼠睾丸间质细胞在性发育过程中的5 α-还原酶活性 成熟;和3）cAMP引起类固醇生成的机制 使用新开发的小鼠Leydig细胞培养系统进行脱敏。 这第三个具体目标将研究cAMP引起的机制， 微粒体和线粒体P-450酶活性下降， 微粒体和线粒体P-450降低之间的关系 活性、底物消耗和最大睾酮减少 生产 将使用[3 H]标记的类固醇研究酶活性 底物并在提取后测量[3 H]标记的类固醇产物， 通过薄层色谱法纯化类固醇。 使用体内和体外相结合的拟议研究 研究睾丸间质细胞功能调节的方法将有助于 更好地理解决定最大睾酮的过程 在生命的不同阶段和不同病理条件下的生产 条件

The long term objective of this project is to characterize the mechanisms that determine the capcity of Leydig cells to produce testosterone. We have approached this problem by studying the relationship of activities of steroid biosynthetic enzymes to maximal testosterone production in two functionally distinct populations of Leydig cells from normal and gonadotropin-treated rats. The specific aims of the present study are designed to evaluate additional sites in the steroidogenic pathway that may be decisive in determining Leydig cell capacity for testosterone production as well as to elucidate the mechanisms by which luteinizing hormone (LH) and cAMP either increase or decrease maximal testosterone production depending on the mode of their administration. Specifically we will determine: 1) whether the activity of the cholesterol side chain cleavage enzyme (P-450scc) differs in the two populations of Leydig cells and whether chronic in vivo treatment with LH increases the activity of P-450scc' using homogenates or enriched mitochondrial fractions of Leydig cells separated into two populations by Metrizamide gradient centrifugation; 2) the role of prolactin in the regulation of 5Alpha-reductase activity in purified rat Leydig cells during sexual maturation; and 3) the mechanism by which cAMP brings about steroidogenic desensitization using a newly developed mouse Leydig cell culture system. This third specific aim will examine the mechanisms by which cAMP causes decreases in microsomal and mitochondrial P-450 enzyme activities and the relationship among decreases in microsomal and mitochondrial P-450 activities, substrate depletion and reductions in maximal testosterone production. Enzyme activities will be studied using [3H]-labeled steroid substrates and measuring [3H]-labeled steroid products after extraction and purification of steroids by thin-layer chromatography. The proposed studies using the combination of in vivo and in vitro approaches to study regulation of Leydig cell function will contribute to a better understanding of the processes that determine maximal testosterone production at different stages of life and under different pathological conditions.