MECHANISMS LINKING CALCIUM HOMEOSTASIS AND VASCULAR TONE

建议研究的目的是扩大我们对整个生物体内钙稳态变化与血管功能变化的机制的理解的最新突破。三个特定的目标将检验这一假说，即参与跨细胞Ca~(2+)运动的组织的间隙中发生Ca/2+浓度的动态变化；这些变化通过引起驻留阻力动脉的感觉神经依赖性松弛来调节动脉张力；这种松弛发生在Ca~(2+)诱导的细胞外Ca~(2+)受体的激活与血管扩张递质的释放相结合之后。支持这一假说的初步数据包括：在生理条件下，十二指肠粘膜下层的间质钙离子在1-2 mm之间经历动态变化，这一范围内的钙离子引起神经介导的肠系膜动脉松弛，以及血管周围扩张神经表达与甲状旁腺和肾CAR同源的钙受体(CAR)，该受体将细胞外Ca/2+的变化与细胞功能的变化联系在一起。具体目标1将使用原位微透析方法来检验这样的假设，即参与跨细胞钙离子移动的组织(即十二指肠、肾脏和股骨)的间质钙离子浓度(Ca/ISF)在生理或药物刺激(包括摄入不同水平的膳食钙/2+)的响应下经历动态变化。甲状旁腺激素诱导的钙动员，并用1，25(OH)2维生素D3亚慢性治疗。《特定目标2》将使用线式肌成像术和基于视频尺寸分析的动脉造影术来检验这一假说，即从参与钙/2+跨细胞运动的组织中分离出来的阻力动脉中存在钙/2+诱导的扩张。特殊目标3将使用天然和合成的钙/2+受体配体、出生后发育模型和CAR基因敲除小鼠来测试血管周围感觉神经CAR介导钙/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)关于这种新的钙激活的扩张器系统在连接空洞动物的钙/2+稳态和心血管功能中所起的生理作用的新信息；(B)对钙/2+诱导的扩张是由感觉神经介导的假说的关键检验；以及(C)可能为开发新的控制血压的药物手段提供基础。

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.