ONTOGENY OF DOPAMINE RECEPTOR/G-PROTEIN/EFFECTOR COUPLING

D1样受体对近端肾小管腔的抑制作用 未成熟组的Na/H交换器(NHE)活性明显低于成熟组 动物。在大鼠中，这种减少的效果不是由于NHE，腺苷环化酶 酶或鸟嘌呤核苷酸水平。相反，这是因为它减少了 D_1受体与6-蛋白复合体的偶联效率 是受发育调节的。这可能是由于与年龄有关的差异造成的。 在6-蛋白亚型的分布或数量上，D1样受体 亚型(DIA和DIB)，或影响D1二联体的因素 6种蛋白质的受体。这次竞争性更新的主要目标是 就是要确定调控这个成熟的机制(S) 耦合机制。有三个具体目标。来检验这一假设 G蛋白β/γ亚基介导D1R介导的抑制 肾单位节段对肾小管钠转运的特异性影响 将确定：(A)特定肾单位中G蛋白亚单位的表达 片段，(B)β/γ亚基在第二信使上的作用- 独立调节的肾脏钠转运，以及(C)比例 依赖和非依赖第二信使的D1介导的钠的贡献 转运(腔内NHE和底侧Na-HCO3共转运活性)。我们 也将检验与D1R相关的G蛋白是 发育受调节并受激素影响(例如 糖皮质激素)。2.检验与年龄有关的假设 在D1受体亚型和分布上的差异，我们将确定 这些受体的极区、区域和肾单位节段分布 免疫组织化学染色并定量检测D1R亚型(mRNA和蛋白)。 3.检验存在发育调节的假说 影响D1R/G蛋白偶联的因素，我们将研究 蛋白(如6个蛋白偶联受体蛋白(GRK)、光生蛋白) 胎儿期、幼年期和成熟期D1R/G蛋白偶联的调节 动物。这些研究可能有助于了解D_1受体/G-受体的成熟。 蛋白质偶联，其异常在发病机制中起重要作用 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.