KIDNEY DOPAMINE RECEPTOR FUNCTION IN AGED

描述：(改编自《调查者摘要》)多巴胺和 近端肾小管和肾单位其他区域的D1样受体 在调节肾脏钠排泄方面起着重要作用。初步 研究表明，虽然肾脏中的多巴胺浓度 成年大鼠和老年大鼠的尿液中多巴胺和D1样受体相似 激动剂不能抑制大鼠近曲小管Na，K-ATPase活性 老费舍尔344只老鼠。因此，假设有缺陷的多巴胺 受体、G蛋白偶联和/或细胞信号机制 导致内源性和外源性多巴胺促进能力降低 老年大鼠的钠排泄。这一假设将得到系统的检验。 使用Fischer 344大鼠模型(成年， 中年和老年)。由于已知多巴胺通过以下途径导致钠尿症 抑制Na，K-ATPase和Na，H-交换器活性 分别设计刷子边缘膜实验进行比较 多巴胺对近端两种酶的抑制作用 成年大鼠和老年大鼠肾小管。此后，D1样受体和 将研究其细胞信号级联的组件以调查 多巴胺降低老龄大鼠Na，RATPase反应的机制(S)。 申请者将量化D1样受体的数量和亲和力 基底膜和刷状缘膜及D1a受体mRNA的测定 近端小管上皮细胞D1a受体在老年人的调节 老鼠。D1样受体偶联的G蛋白(Gs和Gq/11)将是 通过蛋白质印迹定量，并用不同的方法测量它们的功能 GTP、NaF等药物以及成人和老年人之间的比较 老鼠。磷脂酶C、蛋白激酶C、腺苷环化酶、蛋白激酶A 和磷脂酶A2是细胞信号转导成分 D_1样受体对心肌细胞Na，K-ATPase和Na，H-交换器活性的影响 近端小管，这些组件的功能状态将被研究 比较它们在成人D1样受体介导的反应中的作用 还有老老鼠。内源性肾脏多巴胺在促钠作用中的作用 将成年大鼠和老年大鼠的排泄物放在正常和 盐摄入量过高和在急性扩容期间。利钠药和 外源性输注多巴胺和D1样受体的利尿作用 激动剂也将在老年和成年大鼠之间进行比较。鉴定 有缺陷的多巴胺反应以及导致这种反应的机制 老龄化现象需要对老年人采取替代治疗方法 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.