REGULATION OF MTAL FUNCTION BY 20-HETE, NO, AND CO

20-HETE、NO 和 CO 对 MTAL 功能的调节

• 批准号: 6578855
• 负责人: Wenhui Wang
• 金额: $ 31.48万
• 依托单位: NEW YORK MEDICAL COLLEGE
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-11-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6578855
• 关键词: calcium channel; calcium indicator; cytochrome P450; dietary potassium; eicosanoid metabolism; eicosanoids; gas chromatography mass spectrometry; heme oxygenase; hypokalemia; ion transport; isolation perfusion; laboratory rat; nitric oxide synthase; potassium channel; renal tubular transport; saluresis; voltage /patch clamp

Hypokalemia impairs the transport function of the thick ascending limb (TAL) and diminishes urinary concentrating ability. Since apical K channels play an important role in K recycling across the apical membrane in the TAL, inhibition of the apical K channels is expected to block the function of the Na/K/Cl cotransporter and to attenuate the urinary concentrating ability. Preliminary results have shown that the activity of apical K channels in the mTAL from animals on a K-deficient diet is significantly lower than those of a high K diet. Moreover, K- depletion increases the production of 20-hydroxyeicosatetraenoic acid and inhibition of cytochrome P450 monoxygenase of arachidonic acid (AA) increases the activity of the apical 70 pS K channels which contribute 80% of K conductance to the apical membrane. Thus, we will test the hypothesis that an increase in cytochrome p450-dependent metabolites of AA is involved in inhibiting the apical K conductance of the TAL in rats on a K-deficient diet. The second hypothesis of Ca2+ sensing receptor is responsible for decreasing the apical K conductance in the TAL from animals on a K-deficient diet. This hypothesis is based on the observation that extracellular Ca2+ concentrations required for inducing a 50% inhibition of the apical 70 pS K channel were significantly lower in the tubules from rats on a K-deficient diet than those on a high K diet. The third hypothesis of the proposal is that a decrease in the activity of nitric oxide synthase (NOS) and heme oxygenase (HO) is responsible for reducing the activity of apical K channels in the TAL from rats on a K- deficient diet. Preliminary data shows that the expression of iNOS and HO-2 decreases in the renal medulla from animals on a K-deficient diet. Moreover, previous studies have shown that NO and CO stimulate the apical 70pS K channels in the mTAL. To achieve our goals, the patch clamp technique, ion-sensitive dye, biochemical approaches and microperfusion techniques will be used to assess effects of AA metabolites, CO and NO on channel activity as well as Na transport in the mTAL.

低钾血症损害粗升支（TAL）的运输功能，降低尿浓缩能力。由于顶端K通道在TAL中跨顶端膜的K再循环中起重要作用，因此预期顶端K通道的抑制将阻断Na/K/Cl协同转运蛋白的功能并减弱尿浓缩能力。初步结果表明，缺钾饮食动物mTAL中顶端K通道的活性显著低于高钾饮食动物。此外，K-耗竭增加了20-羟基二十碳四烯酸的产生，并且花生四烯酸（AA）的细胞色素P450单加氧酶的抑制增加了顶端70 pS K通道的活性，该通道贡献了顶端膜的80%的K电导。因此，我们将测试的假设，细胞色素p450依赖性代谢产物的AA的增加参与抑制顶端钾电导的TAL在大鼠缺钾饮食。第二种假说是钙敏感受体导致缺钾饮食动物TAL顶端钾电导降低。这一假设是基于观察到的细胞外Ca 2+浓度诱导50%的抑制顶端70 pS钾通道显着低于从大鼠的肾小管缺钾饮食比那些高钾饮食。该提议的第三个假设是一氧化氮合酶（NOS）和血红素加氧酶（HO）活性的降低是导致缺钾饮食大鼠TAL中顶端K通道活性降低的原因。初步数据显示，在缺钾饮食的动物肾髓质中，iNOS和HO-2的表达减少。此外，以前的研究表明，NO和CO刺激顶端70 pS钾通道的mTAL。为了实现我们的目标，膜片钳技术，离子敏感染料，生化方法和微灌注技术将被用来评估AA代谢产物，CO和NO对通道活性的影响，以及在mTAL的Na转运。