VASCULAR NA+ PUMP ACTIVITY AND HYPERTENSION

描述(改编自申请人的摘要)：Na+K+ATPase(NKA)是 细胞膜电位的决定因素，并可能有助于 血管平滑肌反应性和张力以及心肌收缩能力，以及 因此可能在高血压的发生和/或维持中发挥作用。这个 酶由α-亚基和β-亚基以及几种亚型组成。 酶是存在的。异构体在物种和组织中表达 在健康和疾病方面似乎受到不同的监管 各州。然而，关于同工酶的功能意义的信息 而对这些蛋白质的调控还远未完成。尤其是， 个体异构体在高血压中的作用及其调节方式 是未知的。 研究人员和其他人此前已经证明，NKA催化 Alpha-2亚单位基因和蛋白表达下调 在几种高血压动物模型的心脏和血管系统中。他们 也表明心脏的下调可以通过以下方式逆转 遗传性高血压大鼠的降压治疗。他们希望 确定这种下调NKAα亚基是否在 血管系统是高血压的一种代偿反应或致病因素。 拟议的研究将通过以下方式区分这些可能性 测试关于这些变化背后的机制的具体假设 在α-2亚基和这一调控的功能后果中 (离子转运和血管紧张性和反应性)在高血压中。这个 具体目标是：(1)检验假设的真实性 血管内压是α-2亚型下调的信号 NKA在血管平滑肌中的表达。这一假说预言， 在以下情况下，α-2亚单位的mRNA将减少 条件：(A)体外培养的主动脉平滑肌细胞暴露于 持续脉动拉伸，(B)分离的灌流大鼠尾动脉暴露 (C)在大鼠的血管系统中 高血压，应该用降压治疗来逆转。 (2)检验压力刺激导致的假设的真实性 (A)血管平滑肌钠泵活动的改变，以及 (B)血管系统的收缩反应性。我们会：(A) 测定细胞内钠泵活性和哇巴因结合部位 暴露在伸展状态。这一假说预测，钠泵的活性 哇巴因结合强度随拉伸强度的增加而降低。(B)决定 血管对血管活性物质的反应性和钠泵的测定 高压长时间灌流后尾动脉的活动性 句号。这一假说预测了钠泵活性的下降和 血管反应性增强。 (3)如果来自目标1和目标2的数据不能支持以下假设 压力下调阿尔法-2，即阿尔法-2的另一种假说 调节下调是高血压的一个原因，因为它导致 血管反应性增强。我们将通过以下方式获得间接证据 下调α-2亚单位并确定血管 响应性。这一假说预测， 由于α-2的下调，动脉会增加。

DESCRIPTION (Adapted from the applicant's abstract): Na+ K+ ATPase (NKA) is a determinant of the cellular membrane potential and can contribute to the vascular smooth muscle reactivity and tone and myocardial contractility, and thus may play a role in development and/or maintenance of hypertension. The enzyme is composed of alpha- and beta-subunits, and several isoforms of the enzyme exist. The isoforms are expressed in a species- and tissue-specific manner and appear to be differently regulated in both health and disease states. However, information on the functional significance of the isozymes and the regulation of these proteins is far from complete. Especially, the role of individual isoforms and the mode of their regulation in hypertension is not known. The investigators and others have previously shown that NKA catalytic alpha-2 subunit gene and protein expressions are downregulated both in the heart and in the vasculature in several animal models of hypertension. They have also shown that the downregulation in the heart can be reversed by antihypertensive treatment in genetically hypertensive rats. They wish to determine whether this downregulation of the NKA alpha-subunit in the vasculature is a compensatory reaction or a causal factor in hypertension. The proposed studies will differentiate between these possibilities by testing specific hypotheses about the mechanisms underlying the alterations in the alpha-2 subunit and the functional consequences of this regulation (ion transport and the vascular tone and reactivity) in hypertension. The specific aims are: (1) To test the veracity of the hypothesis that intravascular pressure is a signal for downregulation of the alpha-2 isoform of NKA in the vascular smooth muscle. This hypothesis predicts that there will be decreases in mRNA for the alpha-2 subunit under the following conditions: (a) in vitro, cultured aortic smooth muscle cells exposed to sustained pulsating stretch, (b) isolated perfused rat tail artery exposed to sustained elevated perfusion pressure, and (c) in the vasculature of rats with hypertension, which should be reversed with antihypertensive treatment. (2) To test the veracity of the hypothesis that pressure stimulus results in an alteration in (a) the activity of the vascular smooth muscle Na-pump, and (b) the contractile responsiveness of the vasculature. We will: (a) measure the Na-pump activity and the [3H]ouabain binding sites in cells exposed to stretch. This hypothesis predicts that both the Na-pump activity and the ouabain binding will decrease with stretching. (b) determine the vascular responsiveness to vasoactive agents and measure the Na-pump activity in tail arteries after perfusing with high pressure for a prolonged period. This hypothesis predicts a decrease in Na-pump activity and an enhancement of vascular reactivity. (3) If the data from Aims 1 and 2 fail to support the hypothesis that pressure downregulates alpha-2, the alternate hypothesis that alpha-2 downregulation is a causal factor to hypertension by contributing to increased vascular reactivity. We will obtain indirect evidence by downregulating the alpha-2 subunit and determining the vascular responsiveness. This hypothesis predicts that the responsiveness of the arteries will increase as a result of alpha-2 downregulation.