HORMONAL INFLUENCES ON THE RENAL MICROVASCULATURE

越来越多的证据表明，肾传入和传出 小动脉依赖于不同的机制来实现激动剂诱导的 细胞内Ca 2+浓度（[Ca 2 +]i）的改变。 这 一项提案将检验肾传入和传出 小动脉对机电耦合的依赖程度不同 （E-MC）机制与VMS细胞，与传入小动脉 与肌膜跨膜电位紧密相关的功能 (Em)传出小动脉功能相对独立于 Em. 如果发生这种情况，肾脏中E-MC的任何破坏 微血管系统应导致选择性传入小动脉 功能障碍 我们推测，E-MC的病理生理破坏 引起传入血管舒张和收缩反应性降低 在胰岛素依赖型糖尿病的超滤阶段 （胰岛素依赖型糖尿病）。 拟议的研究将侧重于描述对 主要钠和水保留肽激素，血管紧张素II （AngII）和精氨酸加压素（AVP）。胞内隔离 荧光探针将用于监测[Ca 2 +]i，[Cl]i，[K+]i 和Em反应的传入和传出小动脉分离， 兔肾 这些研究将确定传入和传出 小动脉对激动剂激活的反应是不同依赖的 对Ca 2+内流和释放事件，以及激活 磷脂酶C、酪氨酸激酶和蛋白激酶C。 VSM细胞 将使用分离自大鼠肾小球前微血管的细胞， 与荧光探针和膜片钳技术一起， 旨在确定Ca 2+激活的K+通道和Ca 2+激活的K+通道的影响。 在激动剂刺激期间激活Em和[Ca 2 +]i上的Cl通道。 从链脲佐菌素处理的大鼠中收获的肾小球前VSM细胞将 用于针对IDDM期间E-MC中特定畸变的研究。 将使用荧光二氢吡啶来确定 传入小动脉L型电压门控性钙通道（VGCC） 减少，而膜片钳研究将考虑的机制， 可能是肾小球前VSM中VGCC功能抑制的基础 在IDDM期间。 其他的研究将测试这一假设，即增强的 K+通道（Ca 2+激活和/或ATP激活）的超极化影响。 也伴随着IDDM。 对于拟议工作的所有方面， 细胞水平的研究将得到平行研究的补充 详细说明了推定的信号事件对 血管收缩反应的传入和传出小动脉 灌注的延髓微血管。 我们预计， 研究将提供独特的信息， 参与肾脏微血管的激素控制， 正常情况下和在IDDM的超滤阶段。

Accumulating evidence suggests that renal afferent and efferent arterioles rely on disparate mechanisms to achieve agonist-induced alterations in intracellular Ca2+ concentration ([Ca2+]i). This proposal will examine the hypothesis that renal afferent and efferent arterioles are differentially reliant upon electromechanical coupling (E-MC) mechanisms operative with VMS cells, with afferent arteriolar function being tightly linked to sarcolemmal transmembrane potential (Em) and efferent arteriolar function being relatively independent of Em. If this situation occurs, any disruption of E-MC in the renal microvasculature should result in selective afferent arteriolar dysfunction. We postulate that a pathophysiological disruption of E-MC engenders afferent vasodilation and reduced contractile responsiveness during the hyperfiltration stage of insulin-dependent diabetes mellitus (IDDM). The proposed studies will focus on delineating responses to the primary sodium- and water-retaining peptide hormones, angiotensin II (AngII) and arginine vasopressin (AVP). Intracellularly sequestered fluorescent probes will be utilized to monitor [Ca2+]i, [CI]i., [K+]i and Em responses in afferent and efferent arterioles isolated from rabbit kidney. These studies will determine if afferent and efferent arteriolar responses to agonist activation are differentially dependent on Ca2+ influx and release events, as well as activation of phospholipase C, tyrosine kinase, and protein kinase C. VSM cells isolated from the rat preglomerular microvasculature will be used, together with fluorescent probes and patch clamp techniques, in studies designed to determine the impact of Ca2+-activated K+ channels and Ca2+- activated CI channels on Em and [Ca2+]i during agonist stimulation. Preglomerular VSM cells harvested from streptozocin-treated rats will be used in studies targeting specific aberrations in E-MC during IDDM. A fluorescent dihydropyridine will be used to determine if the number of afferent arteriolar L-type voltage-gated Ca2+ channels (VGCCs) is reduced in IDDM, while patch clamp studies will consider mechanisms that might underlie a functional suppression of VGCCs in preglomerular VSM during IDDM. Other studies will test the postulate that an enhanced hyperpolarizing influence of K+ channels (Ca2+-activated and/or ATP- sensitive) also accompanies IDDM. For all aspects of the proposed work, studies at the cellular level will be complemented by parallel studies detailing the functional impact of the putative signaling events on vasoconstrictor responsiveness in afferent and efferent arterioles of the perfused juxtamedullary microvasculature. We anticipate that these studies will provide unique information detailing cellular events involved in hormonal control of the renal microvasculature, both under normal conditions and during the hyperfiltration stage of IDDM.