ONTOGENY OF DOPAMINE RECEPTOR/G-PROTEIN/EFFECTOR COUPLING

D1样受体抑制近端肾小管管腔的能力 Na+/H+交换器（NHE）活性在未成熟期远低于成熟期 动物在大鼠中，降低的效果不是由于NHE，腺苷酸环化酶 酶或鸟嘌呤核苷酸水平。相反，这是由于减少 D1受体与6-蛋白复合物之间的偶联效率， 是受发育调控的这些可能是由于年龄相关的差异 6种蛋白亚型、D1样受体 亚型（DIA和DIB），或影响D1偶联的因素 6种蛋白质的受体。 此次竞争性更新的主要目标 是为了确定调节这种成熟的机制， 耦合机制有三个具体目标。为了验证这个假设， G蛋白β/γ亚单位介导D1受体介导的抑制 肾单位段对肾小管钠转运的特异性作用，我们 将确定：（a）G蛋白亚单位在特定肾单位中的表达 片段，（B）β/γ亚基对第二信使的作用， 独立调节的肾脏Na+转运，和（c）比例 第二信使依赖性和非依赖性D1介导的Na+的贡献 运输（管腔NHE和基底外侧Na-HCO 3共运输活性）。我们 还将测试D1受体连接的G蛋白是 受发育调节和激素影响（例如， 糖皮质激素）。2.为了验证年龄相关的假设， D1受体亚型和分布的差异，我们将确定 这些受体的极性、区域和肾单位段分布， 免疫组织化学和定量D1受体亚型（mRNA和蛋白质）。 3.为了验证这一假设，即存在发育调节， 影响D1受体/G蛋白偶联的因素，我们将研究 蛋白质（例如6蛋白偶联受体激酶（GRK），糖蛋白）， 在胎儿、未成熟和成熟中调节D1受体/G蛋白偶联 动物这些研究可能有助于阐明D1受体/G- 蛋白偶联，其异常在发病机制中是重要的 遗传性高血压

The ability of D1-like receptors to inhibit proximal tubular luminal Na+/H+ exchanger (NHE) activity is much less in immature than in mature animals. In rats, the decreased effect is not due to NHE, adenylyl cyclase enzyme or guanine nucleotide levels. Rather, it is due to decreased coupling efficiency between the D1 receptor to the 6-protein complex which is developmentally regulated. These may be due to age-related differences in distribution or quantity of 6-protein subtypes, D1-like receptor subtypes (DIA and DIB), or factors that influence the coupling of D1 receptors to 6 proteins. The major objective of this competitive renewal is to determine the mechanism(s) that regulates the maturation of this coupling mechanism. There are 3 specific aims. To test the hypothesis that G-protein beta/gamma subunits mediate the D1-receptor-mediated inhibition of nephron segment specific effect on renal tubular sodium transport, we will determine: (a) G-protein subunit expression in specific nephron segments, (b)the role of beta/gamma subunits on second messenger- independent-regulated renal Na+ transport, and (c) the proportional contribution of second messenger dependent and independent D1-mediated Na+ transport (luminal NHE and basolateral Na-HCO3 co-transport activity). We will also test the hypothesis that D1-receptor-linked G-proteins are developmentally regulated and under hormonal influence (e.g. glucocorticoids). 2. To test the hypothesis that there are age-related differences in D1 receptor subtype and distribution, we will determine the polar, regional, and nephron segment distribution of these receptors by immunohistochemistry and quantify D1 receptor subtype (mRNA and protein). 3. To test the hypothesis that there is developmental regulation of factors that influence D1 receptor/G-protein coupling, we will study proteins (e.g. 6 protein-coupled receptor kinases (GRK), phosducin) that regulate D1 receptor/G-protein coupling in fetal, immature, and mature animals. These studies may shed light on the maturation of D1 receptor/G- protein coupling, an abnormality of which is important in the pathogenesis of genetic hypertension.