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

描述：细胞机制调节张力在慢性缺氧 肺循环定义不清。 越来越多的证据 提示肺血管张力的内皮控制改变在肺血管张力的调节中起作用。 在肺动脉高压（PHT）中起关键作用， 内皮素-1（ET-1）的表达。 研究人员的数据表明， ET-1通过刺激Ca ~（2+）通过Ca ~（2+）通道内流而起作用， L型通道，可能是低阈值电压门控（T型）Ca 2 + 渠道 然而，ET-1与PA平滑肌细胞（SMC） 高血压肺循环膜电位和钙内流 在细胞水平上还没有被定义。 此外，问题是 慢性缺氧对肺动脉平滑肌细胞离子通道表达的影响 调控 虽然已知慢性低氧性PHT降低宏观 PA SMC中的K+电流可能使细胞更加去极化， 慢性缺氧对肺动脉平滑肌细胞离子通道的影响及其机制 离子通道激活通过什么改变是未知的。 因为大多数 研究利用慢性缺氧动物， 缺氧本身是否改变PA SMC离子通道功能，或者是否 血液动力学应激和介质如ET-1起作用。 也不得而知 主要的“正常”PA SMC群体是否分化为 “高血压”表型，或者相反， 的细胞组成性表达这种表型的扩展内， 重塑PA壁。 调查人员将检验以下假设： 慢性肺动脉高压：1）ET-1引起肺动脉平滑肌细胞去极化 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)钙离子进入的新途径 ET-1和缺氧发展，包括低阈值电压操作的Ca 2 + 渠道 3)缺氧、机械应激和/或ET-1导致 将“正常”PA SMC分化为高血压表型（即： 减少的K+通道和新的Ca 2+通道）。 作为目标3的必然结果， 从肺动脉高压小牛中分离的PA SMC的独特群体 稳定表达缺氧敏感或耐缺氧生长的细胞， 比较，检测通道表达和[Ca 2 +] i ]i法规存在。

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.