KIDNEY DOPAMINE RECEPTOR FUNCTION IN AGED

描述：（改编自研究者摘要）多巴胺和 近端小管和肾单位其他区域的D1样受体 在调节肾脏钠排泄中起重要作用。 初步 研究表明，虽然肾脏中的多巴胺浓度 成年和老年大鼠尿中多巴胺和D1样受体 激动剂不能抑制近端小管中Na，K-ATP酶的活性， 老费希尔344大鼠。 因此，我们假设有缺陷的多巴胺 受体、G蛋白偶联和/或细胞信号传导机制将 导致内源性和外源性多巴胺促进 老年大鼠的钠排泄。 这一假设将得到系统的检验 在生物化学和功能上使用Fischer 344大鼠模型（成年， 中年和老年）。 由于多巴胺已知会引起尿钠排泄 抑制基底外侧膜Na，K-ATP酶和Na，H-交换酶活性， 刷状缘膜，分别设计实验进行比较 多巴胺对近端神经元中两种酶的抑制作用 成年和老年大鼠肾小管。 此后，D1样受体和 将研究其细胞信号级联的组成部分， 多巴胺降低老年大鼠Na ~+、RAT_2受体反应性的机制。 申请人将定量D1样受体的数量和亲和力， 基底外侧膜和刷状缘膜，并测量D1 A受体mRNA在 近端小管，以确定老年人D1 A受体调节 大鼠 D1样受体偶联的G蛋白（Gs和Gq/11）将被 通过蛋白质印迹法定量，并使用各种方法测量它们的功能。 GTP、NaF等药物，并与老年人进行比较 大鼠 磷脂酶C、蛋白激酶C、腺苷酸环化酶、蛋白激酶A 和磷脂酶A2是细胞信号传导成分， D1样受体对心肌细胞Na，K-ATPase和Na，H-交换酶活性的影响 近端小管，这些组件的功能状态将进行研究 比较它们在成人D1样受体介导的反应中的作用， 老老鼠 肾脏内源性多巴胺在促钠代谢中的作用 将比较置于正常环境中的成年和老年大鼠的排泄， 高盐摄入和急性容量扩张期间。 促尿钠排泄和 外源性多巴胺和D1样受体的利尿作用 还将在老年大鼠和成年大鼠之间比较激动剂。 识别 多巴胺反应的缺陷以及导致这种情况的机制 在老年人中， 需要使用多巴胺改善肾功能的患者。

DESCRIPTION: (Adapted from the Investigator's Abstract) Dopamine and D1-like receptors in the proximal tubules and other regions of the nephron play an important role in regulating renal sodium excretion. Preliminary studies have demonstrated that while dopamine concentration in the kidney and urine was similar in adult and old rats, dopamine and D1-like receptor agonist failed to inhibit Na,K-ATPase activity in the proximal tubules of old Fischer 344 rats. Therefore, it is hypothesized that defective dopamine receptors, G protein-coupling and/or cellular signaling mechanisms would lead to a reduced ability of endogenous and exogenous dopamine to promote sodium excretion in old rats. This hypothesis will be systematically tested both biochemically and functionally using Fischer 344 rat model (adult, middle aged and old). Since dopamine is known to cause natriuresis by inhibiting Na,K-ATPase and Na,H-exchanger activities on basolateral and brush border membranes, respectively, experiments are designed to compare the inhibitory effects of dopamine on both the enzymes in the proximal tubules of adult and old rat. Thereafter, D1-like receptor and the components of its cellular signaling cascade will be studied to investigate the mechanism(s) of reduced response of dopamine on Na,RATPase in old rats. The applicant will quantify D1-like receptor numbers and affinity in the basolateral and brush border membranes and measure D1A receptor mRNA in the proximal tubules in order to determine D1A receptor regulation in the old rats. The D1-like receptor-coupled G proteins (Gs and Gq/11) will be quantified by western blotting and their function measured using various agents such as GTP, NaF and a comparison will be made between adult and old rats. Phospholipase C, protein kinase C, adenylyl cyclase, protein kinase A and phospholipase A2 are the cellular signaling components that mediate D1-like receptor response on Na,K-ATPase and Na,H-exchanger activity in the proximal tubules, the functional status of these components will be studied to compare their role in D1-like receptor -mediated response in the adult and old rats. The role of endogenous kidney dopamine in promoting sodium excretion will be compared between adult and old rats placed on normal and high salt intake and during acute volume expansion. Natriuretic and diuretic effects of exogenously infused dopamine and D1-like receptor agonists will also be compared between old and adult rats. Identification of a defective dopamine response and the mechanism leading to this phenomenon in aging would require an alternate therapeutic approach in older patients requiring the use of dopamine for improvement of renal function.