EFFECTS OF HYPOXIA, ET-1 AND NO ON PA SMC ION CHANNELS

慢性低氧肺组织张力调节的细胞机制 流通领域界定不清。越来越多的证据表明 改变的内皮细胞对肺血管张力的控制起着关键作用 在肺动脉高压(PHT)中的作用。我们发现血管内皮细胞受到抑制 一氧化氮合酶(NOS)揭示了一种有效的血管收缩刺激 低氧/高血压大鼠肺组织主要由ET-1介导。这些 抑制剂研究还表明，ET-1通过刺激钙离子发挥作用 通过钙离子通道的内流要比L式的通道低 阈值电压门控钙通道。然而，连接ET-T的机制- 1、血管内皮细胞膜电位和钙内流 细胞水平的高血压性肺循环尚未 已定义。此外，还有一个问题是慢性低氧对PA的影响 SMC离子通道的表达与调控。虽然我们知道慢性病 缺氧性PHT减少了PA SMC的宏观结构，这可能导致细胞 更去极化，慢性低氧对PA SMC离子的全面影响 通道和离子通道激活的机制 被改变的都是未知的。一氧化氮合酶抑制剂在高血压肺中的应用结果 确定NO在调节PA音调中的重要作用。虽然它已经 一般认为NO通过SMC环鸟苷起作用 一磷酸(CGMP)和蛋白激酶G(PKG)磷酸化靶标 蛋白质，包括离子通道，以前的大部分工作已经完成 从正常血压循环研究SMC。我们的初步数据 提示在高血压肺循环中存在一种新的机制 对NO的作用不依赖于PKG介导的磷酸化，可能在 在调节基础血管张力方面起着重要作用。我们的四个具体目标 是为了检验以下假设：1)ET-1引起膜去极化 抑制延迟整流钾通道和抑制高血压PA SMC 激活PA SMC非选择性阳离子通道。2)新的路线 ET-1和低氧引起的CA2进入，包括Low 阈值电压操作的钙通道。3)NO和cGMP对细胞周期的调节 ET-1调节通道的活性，包括环核苷酸门控 (CNG)通道，在高血压抵抗的PA SMC。4)刺激 对于PA SMC通道调节的改变(K通道和 新的钙通道)既可用于低氧，也可用于血流动力学应激。

Cellular mechanisms regulating tone in the chronically hypoxic pulmonary circulating are poorly defined. A growing body of evidence suggests alterated endothelial control of pulmonary vascular tone plays a critical role in pulmonary hypertension (PHT). We found inhibition of endothelial nitric oxide synthase (NOS) unmasks a potent vasoconstrictor stimulus in the hypoxic/hypertensive rat lung which is largely mediated by ET-1. These inhibitor studies also suggest that ET-1 is acting by stimulating Ca2+ influx through Ca2+ channels than the L-type channel, possibly low threshold voltage-gated Ca2+ channels. However, the mechanisms linking ET- 1, PA smooth muscle cells (SMC) membrane potential and Ca2+ influx in the hypertensive pulmonary circulation at the cellular level have not been defined. Additionally in question is the effect of chronic hypoxia on PA SMC ion channel expression and regulation. While it is known that chronic hypoxic PHT reduces macroscopic on PA SMCs, which might render the cells more depolarized, the full effect of chronic hypoxia on PA SMC ion channels and the mechanisms through which ion channel activation is altered are unknown. Results with NOS inhibitors in the hypertensive lung establish an important role for NO in modulating PA tone. While it has been generally assumed that NO acts through SMC cyclic guanosine monophosphate (cGMP) and protein kinase G (PKG) to phosphorylate target proteins, including ion channels, the majority of prior work has been done studying SMC from the normotensive circulation. Our preliminary data suggests that in the hypertensive pulmonary circulation a novel mechanisms of action for NO, independent of PKG-mediated phosphorylation, may play in important role in modulating basal vascular tone. Our four specific aims are to test the hypotheses that: 1) ET-1 causes membrane depolarization of hypertensive PA SMCs via inhibition of delayed rectifier K+ channels and activation of PA SMC non-selective cation channels. 2) Novel routes of Ca2+ entry in response to ET-1 and hypoxia develop, including low threshold voltage operated Ca2+ channels. 3) NO and cGMP modulate the activity of ET-1 regulated channels, including cyclic nucleotide gated (CNG) channels, in hypertensive resistance PA SMCs. And 4) The stimulus for alterations in PA SMC channel regulation (decreased K+ channels and novel Ca2+ channels) is either for both hypoxia and hemodynamic stress.