MECHANISMS LINKING CALCIUM HOMEOSTASIS AND VASCULAR TONE

所提出的研究的目标是扩大在我们的机制的理解，偶联的变化在整个生物体Ca2+稳态与血管功能的改变的最新突破。三个特定的目标将验证Ca/2+浓度的动态变化发生在参与跨细胞Ca2+运动的组织间质空间的假设；这些变化通过引起常驻阻力动脉的感觉神经依赖性松弛来调节动脉张力；Ca2+诱导的细胞外Ca2+受体的激活与血管扩张剂递质的释放相结合，导致了这种放松。支持这一假设的初步数据包括：在生理条件下，十二指肠粘膜下层间质Ca2+经历1 - 2mM的动态变化，Ca2+在这个范围内引起离体肠系膜动脉神经介导的松弛，以及血管周围扩张神经表达一种与甲状旁腺和肾CaR同源的Ca2+受体（CaR）的分子证据，该CaR将细胞外Ca/2+的变化与细胞功能的改变相结合。特异性目标1将使用原位微透析方法来验证组织间质Ca2+ (Ca/isf)浓度参与跨细胞Ca2+运动的假设；即十二指肠、肾脏和股骨，在生理或药理学刺激下（包括摄入不同水平的膳食钙/2+）会发生动态变化。甲状旁腺激素诱导的Ca2+动员和1,25 (OH)2维生素D3的亚慢性治疗。Specific aim 2将使用钢丝肌造影和基于视频维度分析的动脉造影来检验Ca/2+诱导的扩张发生在从Ca/2+跨细胞运动组织分离的阻力动脉中的假设。Specific aim 3将使用Ca/2+受体的天然和合成配体、出生后发育模型和CaR敲除小鼠来验证血管周围感觉神经CaR介导Ca/2+诱导的神经依赖性松弛的假设。我们预计这些研究将提供(a)关于这种新型Ca/2+激活的扩张系统在连接孔动物Ca/2+稳态和心血管功能方面所起的生理作用的新信息，(b)对Ca/2+诱导的扩张是由感觉神经CaR介导的假设的关键测试，以及(c)可能为开发新的药理学方法提供基础操纵血压。

The goal of the proposed studies is to expand upon a recent breakthrough in our understanding of the mechanisms that couple changes in whole organism Ca2+ homeostasis with alterations in vascular function. Three specific aims will test the hypothesis that dynamic change sin the concentration of Ca/2+ occur in interstitial space of tissues involved in transcellular Ca2+ movement; these changes modulate arterial tone by causing sensory nerve dependant relaxation of resident resistance arteries; and the relaxation occurs secondary to Ca2+-induced activation of a receptor for extracellular Ca2+ that is coupled with the release of vasodilator transmitter. Preliminary data that support this hypothesis include the finding that under physiologic conditions, interstitial Ca2+ in the duodenal sub-mucosa undergoes dynamic changes between 1 and 2mM, that Ca2+ in this range causes nerve mediated relaxation of isolated mesenteric arteries, and molecular evidence that perivascular dilator nerve express a Ca2+ receptor (CaR) that is homologous with the parathyroid and renal CaRs that couple changes in extracellular Ca/2+ with alterations in cell function. Specific aim 1 will use an in situ microdialysis method to test the hypothesis that the concentration of interstitial Ca2+ (Ca/isf) in tissues involved in transcellular Ca2+ movement; i.e., the duodenum, kidney, and femur, undergoes dynamic changes in response to physiologic or pharmacologic stimuli including intake of varying levels of dietary Ca/2+. parathyroid hormone-induced Ca2+ mobilization, and sub-chronic treatment with 1,25 (OH)2 vitamin D3. Specific aim 2 will use wire myography and video dimension analysis-based arteriography to test the hypothesis that Ca/2+-induced dilation occurs in resistance arteries isolated from tissues involved in transcellular movement of Ca/2+. Specific aim 3 will use natural and synthetic ligands of the Ca/2+ receptor, a postnatal development model, and the CaR knockout mouse to test the hypothesis that the perivascular sensory nerve CaR mediates nerve dependent relaxation induced by Ca/2+. We anticipate that these studies will provide (a) new information about the physiologic role that this novel Ca/2+-activated dilator system plays in linking hole animal Ca/2+ homeostasis and cardiovascular function, (b) a critical test of the hypothesis that the Ca/2+-induced dilation is mediated by a sensory nerve CaR, and (c) may provide the basis for the development of novel pharmacologic means of manipulating blood pressure.