MECHANISMS LINKING CALCIUM HOMEOSTASIS AND VASCULAR TONE

拟议的研究的目标是扩大我们的理解，耦合在整个生物体的Ca 2+稳态的变化与血管功能的改变的机制，最近的突破。三个具体的目标将检验这样的假设，即Ca/2+浓度的动态变化发生在涉及跨细胞Ca 2+运动的组织的间隙中，这些变化通过引起驻留阻力动脉的感觉神经依赖性舒张来调节动脉张力;并且该舒张继发于Ca 2+诱导的细胞外Ca 2+受体的激活，其与血管舒张递质的释放偶联。支持这一假设的初步数据包括以下发现：在生理条件下，十二指肠粘膜下层中的间质Ca 2+在1和2 mM之间经历动态变化，该范围内的Ca 2+引起神经介导的离体肠系膜动脉舒张，以及血管周围扩张神经表达Ca 2+受体（CaR）的分子证据其与甲状旁腺和肾汽车同源，其将细胞外Ca/2+的变化与细胞功能的改变偶联。具体目标1将使用原位微透析方法来检验以下假设：组织中的间质Ca 2+浓度（Ca/isf）涉及跨细胞Ca 2+运动;即，十二指肠、肾和股骨响应生理或药理刺激（包括摄入不同水平的饮食Ca/2+）而经历动态变化。甲状旁腺疾病诱导的Ca 2+动员，和亚慢性治疗与1，25（OH）2维生素D3。具体目标2将使用导丝肌造影术和基于视频维度分析的动脉造影术来检验Ca/2+诱导的扩张发生在从涉及Ca/2+跨细胞运动的组织中分离的阻力动脉中的假设。具体目标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敲除小鼠来测试血管周围感觉神经CaR介导由Ca/2+诱导的神经依赖性松弛的假设。我们预期这些研究将提供（a）关于这种新型Ca/2+激活的扩张系统在连接动物Ca/2+稳态和心血管功能中所起的生理作用的新信息，（B）Ca/2+诱导的扩张由感觉神经CaR介导的假设的关键检验，和（c）可以为开发控制血压的新药理学手段提供基础。

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.