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

慢性低氧肺动脉张力调节的细胞机制 循环定义不明确。越来越多的证据表明 肺血管张力的内皮控制改变在 肺动脉高压（PHT）。我们发现， 一氧化氮合酶（NOS）揭示了一种有效的血管收缩刺激， 缺氧/高血压大鼠肺组织中ET-1的表达在很大程度上是由ET-1介导的。这些 抑制剂研究还表明，ET-1通过刺激Ca 2+起作用， 通过Ca 2+通道的内流比L型通道，可能较低 阈值电压门控Ca 2+通道。然而，与ET- 1、PA平滑肌细胞（SMC）膜电位和Ca ~（2+）内流 高血压肺循环在细胞水平上还没有被 定义了此外，慢性缺氧对PA的影响也存在疑问。 SMC离子通道的表达和调节。虽然众所周知，慢性 缺氧PHT可使PA SMC的宏观损伤减少，这可能使细胞 慢性缺氧对PA SMC离子的影响 离子通道和离子通道激活的机制 改变是未知的。高血压肺中NOS抑制剂的结果 确立了NO在调节PA张力中重要作用。虽然它有 一般认为NO通过SMC环鸟苷起作用 蛋白激酶G（PKG）的磷酸化靶点 蛋白质，包括离子通道，大多数先前的工作已经完成， 研究正常血压循环中的SMC。我们的初步数据 提示在高血压肺循环中， NO的作用，独立于PKG介导的磷酸化，可能在 在调节基础血管张力中起重要作用。四个具体目标 ET-1可引起心肌细胞膜去极化， 通过抑制延迟整流钾通道和 PA SMC非选择性阳离子通道的激活。2)新路线 Ca 2+内流响应ET-1和缺氧发展，包括低 阈值电压控制的钙通道。3)NO和cGMP调节 ET-1调节通道的活性，包括环核苷酸门控 (CNG)通道，在高血压阻力PA SMC。（4）刺激 PA SMC通道调节的改变（K+通道减少， 新的Ca 2+通道）是缺氧和血液动力学应激的。

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.