Exppression and function of two paracrine hormonal regulation of nephron

描述：（改编自申请人的摘要）肾素管腔中肾素-血管紧张素系统（RAS）和钾素-激肽系统（KKS）的表达必须通过肾脏对钠和水的处理影响循环稳态。关于这些系统的调节和功能的假设将使用小鼠作为实验模型进行测试。他们提出旁分泌RAS沿整个肾元作用，涉及近端小管（PT）起源的血管紧张素原（AGT）和连接小管（CNT）合成和分泌的肾素。在随后的工作中，他们发现肾素和组织钾化因子是由碳纳米管的相同细胞表达的。主要假设是管状RAS和KKS在调节最终钠排泄中发挥密切相关的旁分泌功能；这两种系统后来被称为肾素-钾化酶系统（RKS）。他们将测试以下几个特定的假设：(1)饮食钠对RKS激素前体的调节，(2)对饮食盐反应的菌株特异性差异的遗传基础，以及(3)PT血管紧张素原表达和遗传背景在动脉压（AP）调节中的意义。这些激素成分与肾脏对钠和水的处理之间的关系将通过以下实验进行测试：(1)通过血浆容量的一致性或不一致性改变来操纵膳食钠会破坏钠平衡；(2)利尿剂选择性改变肾元重吸收，可控制肾元不同部位的节段性钠和液体输送；(3)通过特异性药理抑制，探讨肾小管RKS在肾钠处理中的意义。钠味觉和碳纳米管肾素表达对阿米罗得依赖性的一致菌株差异表明，菌株之间存在一个或多个参与或受上皮细胞钠进入调节的基因差异。他们建议在选择菌株的回交中通过连锁分析来绘制这些基因，并根据候选基因策略确定因果突变。为了测试PT血管紧张素原和遗传背景对基线AP的重要性，将在两种不同背景下表达一到三个AGT基因的转基因动物中检测管状RKS对持续改变饮食钠的反应。

DESCRIPTION: (Adapted from the applicant's abstract) Expression of both a renin-angiotensin system (RAS) and a kallilrein-kinin system (KKS) in tubular lumen of the nephron must impact on circulatory homeostasis through renal handling of sodium and water. Hypotheses regarding the regulation and function of these systems will be tested using the mouse as an experimental model. They have proposed that a paracrine RAS operates along the entire nephron that involves angiotensinogen (AGT) of proximal tubule (PT) origin and renin synthesized and secreted by connecting tubule (CNT). In subsequent work, they have found that renin and tissue kallikrein are expressed by the same cells of CNT. The main hypothesis is that tubular RAS and KKS exert closely interrelated paracrine functions in the regulation of final sodium excretion; these two systems are thereafter referred to as renin- kallikrein system (RKS). They will test specific hypotheses concerning (1) the regulation of hormone precursors of the RKS by dietary sodium, (2) the genetic basis for strain-specific differences in response to dietary salt, and (3) the significance of both PT angiotensinogen expression and genetic background in arterial pressure (AP) regulation. The relationship between these hormonal components and renal handling of sodium and water will be tested through the following experiments: (1) sodium balance will be disrupted by manipulations of dietary sodium with concordant or discordant alteration of plasma volume; (2) segmental sodium and fluid delivery at various sites along the nephron will be manipulated by selective alteration of reabsorption with diuretics; (3) the significance of the tubular RKS in renal sodium handling will be probed by specific pharmacological inhibition. Concordant strain variation in the amiloride-dependance of both sodium taste and CNT renin expression suggest the hypothesis of a genetic difference among strains in one or more genes involved in or regulated by sodium entry in epithelial cells. They propose to map such genes by linkage analysis in backcrosses of select strains and to identify the causal mutations following a candidate gene strategy. To test the significance of PT angiotensinogen and genetic background for baseline AP, the response of the tubular RKS to sustained alterations of dietary sodium will be examined in transgeneic animals expressing one to three AGT genes in two distinct backgrounds.