PARACRINE INTERACTIONS IN PROLACTIN SECRETION

不同类型的垂体腺细胞的明确分布 脑下垂体前叶(AP)提示细胞间的相互作用 在AP的发育、功能和增殖中起重要作用 细胞。该实验室之前的研究表明，降钙素- 类免疫反应肽(PIT-CT)是由 培养的AP细胞。它可能会影响催乳素的功能，因为合成的 SCT是PRL分泌和PRL基因转录的有效抑制因子。 我们最近的研究使用了免疫组织学、细胞培养和 PIT-CT基因和PIT-CT的分子生物学研究 IR肽由促性腺激素和RC4B细胞(肿瘤)选择性表达 促性腺激素细胞)，而不是αT-3、GH3或AT20细胞。 在时间上，PIT-CT基因的表达是在之后开始的，而不是 在此之前，由于PIT-CT mRNA可以表达LHBeta亚基 在αT-3细胞或胎儿AP腺中未检测到(胚胎第19天)， 但在胎龄20天的AP腺体中可检测到。这些研究 在成人AP腺体已显示PIT-CT IR促性腺激素被包围 杯状乳汁管，提示小窝CT在旁他克林中的作用 抑制催乳素功能。PIT-CT的生理意义 结果表明，PIT被动免疫是一种有效的预防措施。 CT联合抗SCT血清可引起PRL分泌显著增加 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显著增加。三天的E2 治疗导致推测的PIT-CT mRNA丰度下降了9倍 并导致PIT-CT IR浓度下降四倍。在……里面 相比之下，卵巢切除后，PIT-CT IR含量增加了三倍。 因此，PIT-CT是一种新的生理学相关的促性腺激素来源 催乳素功能的抑制剂。既然我们找到了一个推定的坑- CT的cDNA克隆和PIT-CT基因的表达与 表达PIT-CT IR，本提议的目的是 确定PIT-CT在成熟、功能和 乳酸菌在发育和成年期的增殖。特定的 本提案的目的是建立RC4B-Lactotrope共培养模型进行测试 内源性PIT-CT在嗜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新的和重要的发现- 垂体腺功能中的促乳素相互作用。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.