HYPOXIA AND ET-1 EFFECT ON PA SMC EFFECT ON CHANNELS

描述：慢性缺氧症中调节音调的细胞机制 肺循环界限不清。越来越多的证据 提示内皮细胞对肺血管张力的控制改变在 在肺动脉高压(PHT)中的关键作用，以及在 过程I内皮素-1(ET-1)。调查人员的数据表明 ET-1通过非钙离子通道刺激钙离子内流而发挥作用 L型通道，可能是低阈值电压门控(T型)钙离子通道 频道。然而，ET-1与PA平滑肌细胞(SMC)的联系机制 高血压性肺循环中的膜电位和钙离子内流 在细胞水平上还没有被定义。此外，有问题的是 慢性低氧对PA-SMC离子通道表达及蛋白表达的影响 监管。虽然众所周知，慢性缺氧性PHT降低了宏观 PA SMC中的K+电流，这可能使细胞更去极化， 慢性低氧对PA-SMC离子通道的全面影响及其机制 离子通道的激活是通过什么来改变的还不清楚。就像大多数 研究利用了长期缺氧的动物，这也是不确定的 低氧本身是否改变了PA SMC离子通道功能 血流动力学应激和介质，如ET-1，发挥了作用。也是未知的 主要的PA SMC“正常”群体是否分化为 一个“高血压”表型，或者相反，无论是一个独特的亚群 表达这种表型的细胞在体内扩张 改建PA墙。调查人员将测试假设，在 慢性肺动脉高压：1)ET-1引起PA-SMC去极化 通过抑制延迟整流钾通道和激活PA SMC 非选择性阳离子通道。2)钙离子内流的新途径 ET-1与低氧发展，包括低阈值电压操作的钙离子 频道。3)缺氧、机械应激和/或ET-1引起 “正常”PA SMC分化为高血压表型(即： K+通道减少和新的钙通道)。作为目标3的必然结果， 从肺动脉高压小牛分离的PA-SMC的单一种群 哪些STABL表达低氧敏感或耐低氧生长 比较，测试通道表达和[Ca~(2+)]是否发生结构性变化 ]i法规已经存在。

DESCRIPTION: Cellular mechanisms regulating tone in the chronically hypoxic pulmonary circulation are poorly defined. A growing body of evidence suggests that altered endothelial control of pulmonary vascular tone plays a critical role in pulmonary hypertension (PHT), and that a key mediator in the process i endothelin-1 (ET-1). The investigators' data suggest that ET-1 is acting by stimulating Ca2+ influx through Ca2+ channels other than the L-type channel, possibly low threshold voltage-gated (T-type) Ca2+ channels. However, the mechanisms linking ET-1, PA smooth muscle cell (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 tha chronic hypoxic PHT reduces macroscopic K+ currents in PA SMCs, which might render the cells more depolarized, the full effects of chronic hypoxia on PA SMC ion channels and the mechanisms through which ion channel activation is altered are unknown. As most studies have utilized chronically hypoxic animals it is also uncertain whether hypoxia, per se, alters PA SMC ion channel function, or whether hemodynamic stress and mediators, such as ET-1, play a role. Also unknown is whether the predominant "normal" population of PA SMCs differentiate into a "hypertensive" phenotype, or conversely, whether a unique sub-population of cells constitutively expressing this phenotype expand within the remodeling PA wall. The investigators will test the hypotheses that in chronic pulmonary hypertension: 1) ET-1 causes depolarization of 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) Either hypoxia, mechanical stress and/or ET-1 cause differentiation of "normal" PA SMCs into a hypertensive phenotype (i.e.: decreased K+ channels and novel Ca2+ channels). As a corollary to Aim 3, uniqu populations of PA SMCs isolated from pulmonary hypertensive calves which stabl express hypoxia-sensitive or hypoxia-resistant growth will be compared, testin if constitutive alterations in channel expression and [Ca2+ ]i regulation are present.