REGULATION OF RENAL H+/K+ EXCHANGE

哺乳动物肾脏的皮质集合管(CCT) 负责尿液pH值和钾(K)的最终调节 集中精神。这项规定涉及的两种主要细胞类型是 钠转运主细胞与酸碱调节 嵌插细胞。最近的证据表明，胃的存在- 肾集合管中型酸转运体(H-K-ATPase)。这 建议书侧重于在职能上确定的H-K的贡献 交换器(H-K-ATPase)对酸碱和钾动态平衡过程的影响 皮质集合管的嵌合细胞，利用 细胞内pH和钙的荧光测量。 将通过三项相关准备工作实现六项具体目标。 将通过以下方式监控H-K交换机的功能活动 钾依赖的细胞内pH恢复率的测定 对强酸负荷的影响。这种交换剂在钾重吸收中的作用 H的分泌以及pH、K和醛固酮对H的调节。 H-K交换机的基本特性包括评估 交换器与特性良好的胃的功能相似性 H-K-ATPase，交换器的心尖/基底外侧定位，以及 确定其在碱性条件下对细胞内pH调节的贡献 条件。适合选定目标的准备工作包括：拆分 开放的皮质集合管、分离的壁细胞和分离的 灌流的皮质集合管，内含细胞内pH 指示剂BCECF或细胞内钙指示剂Fura-2。此外, 非酯化形式的BCECF和PBFI，一种K特有的指示剂，将 可用于灌流小管的研究。 H-K交换机制的功能表征和定位 这一机制可能有助于解释一些临床观察： 1.低血钾与细胞外碱中毒的关系； 代谢性酸中毒与钾排泄减少的关系 它可以将血清K升高到一个点，它干扰电 心脏的活动。这些研究的结果将提供 有关正常和病理性K状态和意志的重要信息 代谢异常影响我们对钾平衡的理解 还有利尿剂治疗。

The cortical collecting tubule (CCT) of the mammalian kidney is responsible for the final regulation of urine pH and potassium (K) concentration. The 2 major cell types involved in this regulation are the Na-transporting principal cells and the acid-base regulating intercalated cells. recent evidence suggests the presence of a gastric- type acid transporter (H-K ATPase) in the renal collecting duct. This proposal focuses on the contribution of a functionally identified H-K exchanger (H-K ATPase) to the process of acid-base and K homeostasis in intercalated cells of the cortical collecting tubule, utilizing fluorescence measurements of intracellular pH and calcium. Six specific aims will be addressed using three related preparations. The functional activity of the H-K exchanger will be monitored by measuring the rate of K-dependent intracellular pH recovery in response to an imposed acid load. the role of this exchanger in K reabsorption and H secretion and regulation by pH, K and aldosterone will be examined. Basic characterization of the H-K exchanger includes assessing the functional similarity of the exchanger to the well-characterized gastric H-K ATPase, apical/basolateral localization of the exchanger, and defining its contribution to intracellular pH regulation under basal conditions. Preparations appropriate to selected aims include: split open cortical collecting tubules, isolated parietal cells, and isolated perfused cortical collecting tubules, loaded with the intracellular pH indicator, BCECF or the intracellular Ca indicator, Fura-2. In addition, the unesterified forms of BCECF and PBFI, a K-specific indicator, will be used for perfused tubule studies. Functional characterization of an H-K exchange mechanism and localization of this mechanism may help explain a number of clinical observations: 1. the association between low serum K and extracellular alkalosis, 2. the relationship between metabolic acidosis and reduced excretion of K which can elevate serum K to a point where it interferes with electrical activity of the heart. The results of these studies will provide important information on normal and pathological K states and will influence our understanding of K balance during metabolic abnormalities and diuretic therapy.