HORMONAL INFLUENCES ON THE RENAL MICROVASCULATURE

越来越多的证据表明，肾脏的传入和传出 小动脉依赖不同的机制来实现激动剂诱导 细胞内钙离子浓度([Ca2+]i)的变化。这 提案将检验肾脏传入和传出的假设 小动脉不同地依赖于机电耦合 (E-MC)作用于VMS细胞和传入小动脉的机制 与肌膜跨膜电位密切相关的功能 (EM)和传出小动脉功能相对独立于 嗯。如果发生这种情况，肾脏E-MC的任何破坏 微血管构筑应导致选择性传入小动脉 功能障碍。我们推测E-MC的病理生理紊乱 产生传入血管扩张和收缩反应性降低 胰岛素依赖型糖尿病的超滤期 (IDDM)。拟议的研究将侧重于描述对 初级保钠保水肽激素血管紧张素II 血管紧张素Ⅱ(AngII)和精氨酸加压素(AVP)。细胞内隔离 利用荧光探针监测[Ca~(2+)]_i、[CI]_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的依赖关系 钙离子内流和释放事件以及钙离子的激活 磷脂酶C、酪氨酸激酶和蛋白激酶C 从大鼠肾小球前微血管中分离出来的， 结合荧光探针和膜片钳技术，在研究中 旨在确定钙激活的K+通道和钙离子通道的影响 激动剂刺激时激活Em和[Ca~(2+)]i上的CI通道。 从链佐菌素处理的大鼠肾小球前VSM细胞将 可用于针对IDDM期间E-MC特定像差的研究。 荧光二氢吡啶将被用来确定数字是否 传入小动脉L型电压门控性钙通道(VGCC) 减少IDDM，而膜片钳研究将考虑 可能是肾小球前VSM功能抑制VGCC的基础 在IDDM期间。其他研究将检验这一假设，增强的 K+通道(钙激活和/或ATP激活)的超极化影响 敏感)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。 详细说明了假定的信号事件对 大鼠传入和传出小动脉的血管收缩反应性 灌流的延髓旁微血管。我们预计这些 研究将提供详细描述细胞事件的独特信息 参与肾微血管的荷尔蒙控制，两者都在 在正常情况下和在IDDM的超滤期。

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.