PARACRINE INTERACTIONS IN PROLACTIN SECRETION

各种类型的垂体细胞在脑垂体中的明确分布 垂体前叶（AP）腺表明，细胞间的相互作用发挥作用， 在AP的发育、功能和增殖中起重要作用 细胞该实验室以前的研究表明，降钙素- 类免疫反应性肽（pit-CT）由以下细胞合成和分泌： 培养的AP细胞。它可能会影响催乳素功能，因为合成 sCT是PRL分泌和PRL基因转录的有效抑制剂。 我们最近的研究使用了免疫组织学，细胞培养和 分子方法来证明假定的pit-CT mRNA和pit-CT IR肽由促性腺激素和RC 4 B细胞（肿瘤细胞）选择性表达。 促性腺激素系统的细胞），而不是由α T-3、GH 3或AT 20细胞。 时间上，pit-CT基因表达在 在此之前，LH β亚基的表达，因为pit-CT mRNA可以 在α T-3细胞或胎儿AP腺（胚胎第19天）中未检测到， 但在胎龄20天的AP腺中可检测到。研究 在成人AP腺体中，pit-CT IR促性腺激素被包围， 杯状催乳素，提示pit-CT在阿托他克林中的作用 抑制催乳素功能。坑CT的生理意义 结果表明，被动免疫的pit- 用抗sCT血清进行CT，在24小时内引起PRL分泌的急剧增加。 在体外和体内条件下。AP腺体的Pit-CT IR含量变化 在不同的生理条件下，E2的三天 治疗导致假定的pit-CT mRNA丰度下降9倍 并且还导致pit-CT IR浓度降低四倍。在 相比之下，卵巢切除术诱导pit-CT IR含量增加三倍。 因此，pit-CT是一种新的，生理相关的，促性腺激素衍生的 催乳素功能抑制剂。既然我们已经获得了一个假定的坑- CT cDNA克隆和假定的pit-CT mRNA表达与肿瘤的发生和发展有关。 表达坑-CT IR，本提案的目的是 确定pit-CT在成熟、功能和 在发育和成年期间催乳素的增殖。具体 该提案的目的是开发RC 4 B-催乳素共培养模型以测试 内源性pit-CT在催乳素功能和增殖中的作用。 具体目标2将研究促性腺激素耗竭或 pit-CT过表达对催乳素功能的影响。具体目标3和4将 进一步描述性腺类固醇和其他旁分泌的作用， 神经内分泌因素对pit-CT表达的影响。这些研究将 为促性腺激素的作用提供了新的重要发现- 催乳素在垂体功能中的相互作用这些结果将使 对理解正常人生理学的重要贡献 生殖和衰老的病理生理学。

Well-defined distribution of various pituitary cells types in the anterior pituitary (AP) gland suggest that Cell-to-Cell interactions play an important role in the development, function and proliferation of AP cells. Previous studies from this laboratory have shown that calcitonin- like immunoreactive peptide (pit-CT) is synthesized and secreted by cultured AP cells. It may affect lactotrope function because synthetic sCT is a potent inhibitor of PRL secretion and PRL gene transcription. Our recent studies have used immunohistological, cell culture and molecular approaches to demonstrate that putative pit-CT mRNA and pit-CT IR peptide is selectively expressed by gonadotropes and RC4B cells (tumor cells of gonadotropelineage), and not by alphaT-3, GH3 or AT20 cells. Temporally, pit-CT gene expression is initiated subsequent to, and not prior to, the expression of LH Beta-subunits because pit-CT mRNA could not be detected in alphaT-3 cells or fetal AP gland (embryonic day 19), but could be detected in the AP gland of day 20 fetal age. The studies in adult AP glands have shown that pit-CT IR gonadotropes were surrounded by cup-shaped lactotropes, suggesting a role for pit-CT in juxtacrine inhibition of lactotrope function. Physiological significance of pit-CT action was demonstrated by the findings that passive immunization of pit- CT with anti-sCT serum caused a dramatic increase in PRL secretion under in vitro and in vivo conditions. Pit-CT IR content of the AP gland varied significantly in various physiological conditions. Three days of E2 treatment caused a nine-fold decline in putative pit-CT mRNA abundance and also caused four-fold decrease in pit-CT IR concentrations. In contrast, ovariectomy induced a three-fold increase in pit-CT IR content. Thus, pit-CT is a novel, physiologically relevant, gonadotrope-derived inhibitor of lactotrope function. Since we have obtained a putative pit- CT cDNA clone and the expression of putative pit-CT mRNA parallels the expression of pit-CT IR, an objective of the present proposal is to identify the precise role for pit-CT in maturation, function and proliferation of lactotropes during development and adulthood. Specific Aim of the proposal will develop RC4B-lactotrope co-culture model to test the role of endogenous pit-CT in lactotrope function and proliferation. Specific Aim 2 will study the consequence of gonadotrope-depletion or pit-CT overexpression on lactotrope function. Specific Aim 3 and 4 will further characterize the actions of gonadal steroids and other paracrine and neuroendocrine factors on pit-CT expression. These studies will provide new and significant findings towards the role of gonadotrope- lactotrope interactions in pituitary function. These results will make important contributions in understanding physiology of normal reproduction and pathophysiology of aging.