CEREBROVASCULAR POTASSIUM CHANNELS AND HYPERTENSION

描述(改编自申请者摘要)：本项目的目标 是(A)提供有关表达、规则和 钙依赖钾通道(K(Ca)通道)对心肌细胞的保护作用 暴露于慢性高血压的大脑动脉肌膜，以及(B) 确定钾(钙)通道是否代表新的治疗靶点以减少 脑血管张力在这种疾病中的作用。使用西方方法的早期结果 显示α-亚基(造孔亚单位)的表达增加 自发性脑动脉肌膜K(Ca)通道 高血压大鼠(SHR)和血压正常的Wistar京都(WKY)大鼠。 这些数据首次直接证明了K(Ca)的表达 脑血管肌膜上的通道可能受原位的调节 动脉血压水平。重要的是，这种增加的表达 高血压时脑平滑肌细胞膜上的K(Ca)通道 似乎通过K(Ca)通道促进K+外流，因为PI观察到 更高水平的全细胞和单通道K(Ca)电流 高血压大鼠的膜片钳血管肌膜。最后， 使用钾(钙)通道阻滞剂朱砂毒素的血管反应性研究， 提示脑血管肌钾(钙)通道上调 脑微循环中的膜与血管张力相反 高血压。首先，朱砂毒素(100 NM)阻断K(Ca)通道 分离的大脑阻力动脉深度去极化和收缩 来自SHR。第二，10 NM的硫杆菌毒素引发了强烈的收缩 原位自发性高血压大鼠软脑膜小动脉，而WKY大鼠则显示类似的小动脉 仅对钾(Ca)通道阻断有中度收缩反应。这些 结果提示K(Ca)通道表达增强的可能性 在脑血管肌膜上可能提供强大的负反馈 抗血管收缩、促进脑血流的途径 在慢性高血压期间。根据这些初步调查结果，私人投资委员会将 调查表达、功能角色和潜能的变化 脑血管钾(钙)通道在慢性阻塞性肺疾病中的疗效 高血压：(A)应用西方方法比较表达水平 两种模型大鼠脑平滑肌细胞膜K(Ca)通道的变化 (B)使用膜片钳方法 比较全细胞膜密度和单通道特性 脑血管平滑肌细胞膜间钾(Ca)电流 以及(C)使用隔离血管和原位颅窗 方法评价其生理作用和治疗潜力。 钾(钙)通道作为负反馈通路和治疗靶点 高血压病患者脑微循环中的反血管张力 动物。

DESCRIPTION (Adapted from Applicant's Abstract): The goals of this project are (a) to provide new information about the expression, regulation and protective influence of Ca2+- dependent K+ channels (K(Ca) channels) in cerebral arterial muscle membranes exposed to chronic hypertension, and (b) to determine if K(Ca) channels represent novel therapeutic targets to reduce cerebral vascular tone in this disease. Early results using Western methods show an increased expression of the alpha-subunit (pore-forming subunit) of K(Ca) channels in cerebral arterial muscle membranes from spontaneously hypertensive rats (SHR) as compared to normotensive Wistar Kyoto (WKY) rats. These data provide the first direct evidence that the expression of K(Ca) channels in cerebrovascular muscle membranes may be regulated by the in situ level of arterial blood pressure. Importantly, this increased expression of K(Ca) channels in cerebral smooth muscle membranes during hypertension appears to enhance K+ efflux through K(Ca) channels, because the PI observed higher levels of whole-cell and single-channel K(Ca) currents in patch-clamped vascular muscle membranes from hypertensive rats. Finally, vascular reactivity studies using the K(Ca) channel blocker, iberiotoxin, suggest that the upregulation of K(Ca) channels in cerebrovascular muscle membranes opposes vascular tone in the cerebral microcirculation during hypertension. First, iberiotoxin (100 nM)-induced block of K(Ca) channels profoundly depolarized and constricted isolated cerebral resistance arteries from SHR. Second, 10 nM iberiotoxin triggered intense constriction of in-situ SHR pial arterioles, whereas similar arterioles from WKY rats showed only moderate contractions in response to K(Ca) channel block. These results raise the possibility that an enhanced expression of K(Ca) channels in cerebrovascular muscle membranes may provide a powerful negative feedback pathway to oppose vascular constriction and promote cerebral perfusion during chronic hypertension. Based on these initial findings, the PI will investigate changes in the expression, functional role, and potential therapeutic benefit of cerebrovascular K(Ca) channels during chronic hypertension by: (a) applying Western methods to compare expression levels of K(Ca) channels in cerebral smooth muscle membranes from two models of normotensive and of hypertensive rats; (b) using patch-clamp methods to compare the whole-cell membrane density and single-channel properties of K(Ca) currents between cerebrovascular smooth muscle membranes from the same rats; and (c) employing the isolated vessel and the in-situ cranial window methods to evaluate the physiological role and therapeutic potential of K(Ca) channels as negative feedback pathways and therapeutic targets for opposing vascular tone in the cerebral microcirculation of hypertensive animals.