Microvessel O2 Responses in Salt-Sensitive Hypertension

描述（由申请人提供）：局部血流控制机制的改变可能在容量扩张型高血压从心输出量升高到血管阻力持续升高的转变中起主要作用。在许多形式的高血压中，已经证明了小动脉因氧气可用性增加而收缩增强，但关于O2诱导微血管收缩的介导机制知之甚少。细胞色素P450 (CYP450) 4A ω -羟化酶，催化20-HETE（花生四烯酸的血管收缩代谢物）的形成，可能在微循环中起02传感器的作用。本研究探讨了CYP450 4A ω -羟化酶和20-HETE在盐敏感性高血压遗传模型达尔S大鼠和正常褐挪威大鼠13号染色体被替换为达尔S遗传背景的SS.BN13经济大鼠中介导o2诱导的微循环小动脉收缩的作用。SS.BN13经济型大鼠在基因上与达尔S大鼠98%相同，但没有表现出高盐饮食引起的血压升高。要验证的总体假设是，Dahl S型高血压大鼠小动脉对PO2升高的反应增强是由于3个因素之一或组合：20-HETE生成增加，小动脉对20-HETE血管收缩作用的敏感性增加，和/或CYP450 4A ω -羟化酶表达改变。在高盐（HS）和低盐（LS）饮食的Dahl S和SS.BN13大鼠的原位肌肌中，研究20-HETE抑制对PO2升高的小动脉反应的影响。采用RT-PCR和Western blotting检测高、低盐饮食各组Dahl S大鼠和SS.BN13大鼠小动脉和实质细胞中细胞色素P450-4A - omega-羟化酶同工型，并检测PO2升高对小动脉和实质细胞中20-HETE生成的影响。我们还将比较不同时期高盐和低盐饮食的Dahl S大鼠和SS.BN13大鼠的原位微循环对外源性20-HETE的反应。这些研究将有助于进一步了解在02可用性变化期间调节血管张力的机制是如何在高血压和饮食盐摄入量增加期间发生改变的

DESCRIPTION (provided by applicant): Alterations in local blood flow control mechanisms may play a major role in the transition from an elevated cardiac output to a maintained elevation in vascular resistance in volume-expanded forms of hypertension. An enhanced constriction of arterioles, in response to increased O2, availability has been demonstrated in many forms of hypertension, but little is known regarding the mechanisms that mediate O2-induced constriction of microvessels. Cytochrome P450 (CYP450) 4A omega-hydroxylase, which catalyzes the formation of 20-HETE (a vasoconstrictor metabolite of arachidonic acid), may act as an 02 sensor in the microcirculation. This study investigates the role of CYP450 4A omega-hydroxylase and 20-HETE in mediating O2-induced constriction of arterioles in the microcirculation of the Dahl S rat, a genetic model of salt sensitive hypertension, and in SS.BN13 consomic rats, in which chromosome 13 of the normotensive Brown Norway rat is substituted into the Dahl S genetic background. The SS.BN13 consomic rats are 98% identical to the Dahl S rat genetically, but do not exhibit elevated blood pressure in response to high salt diet. The overall hypothesis to be tested is that the enhanced response of arterioles to elevated PO2 in Dahl S hypertensive rats is due to one or a combination of 3 factors: increased 20-HETE production, increased sensitivity of arterioles to the vasoconstrictor effects of 20-HETE, and/or altered expression of CYP450 4A omega-hydroxylase. The effect of 20-HETE inhibition, on arteriolar responses to elevated PO2 will be determined in the in situ cremaster muscle of Dahl S and SS.BN13 rats on high salt (HS) and low salt (LS) diets. Cytochrome P450-4A omega-hydroxylase isoforms in arterioles and parenchymal cells of Dahl S rats and SS.BN13 rats on high and low salt diets will be assessed by RT-PCR and Western blotting, and changes in 20-HETE production in response to elevated PO2 will be measured in arterioles and parenchymal cells. Arteriolar constriction in response to exogenous 20-HETE will also be compared in the in situ microcirculation of Dahl S rats and SS.BN13 rats on high salt and low salt diets for various periods of time. These studies should provide an increased understanding of how the mechanisms that regulate vascular tone during changes in 02 availability, are altered during hypertension and during increases in dietary salt intake