EXPRESSION AND FUNCTIONAL ALTERATION OF POTASSIUM CHANNELS IN VASCULAR SMOOTH MUSCLE AND ENDOTHELIAL CELLS IN HYPERTENSION

1）易卒中自发性高血压大鼠（SHR-SP）动脉平滑肌细胞电压依赖性钾电流（Kv电流）的降低应用膜片钳技术，SHR-SP动脉平滑肌细胞Kv电流的幅值与正常血压对照组Wistar京都大鼠（WKY）相比明显降低。用血管紧张素II受体阻断剂降压治疗SHR-SP可部分恢复正常电流，而年轻大鼠则无此改变。定量RT-PCR结果显示，Kv 2.1mRNA的表达在多种Kv蛋白中均降低。结果表明，持续高血压和/或刺激肾素-血管紧张素系统改变了血管内皮细胞的Kv通道。2）SHR-SP主动脉内皮细胞的Kv电流降低，4-氨基吡啶敏感性Kv电流降低 关于我们 SHR-SP组主动脉内皮细胞凋亡率较WKY组明显升高。SHR-SP组内皮细胞静息膜电位较WKY组去极化程度高。通过使用各种Kv蛋白的抗体，染色的Kv1.5在内皮细胞减少SHR-SP。在主动脉的张力记录，4-amynopyridine的应用损害内皮依赖性舒张，这是部分恢复的预处理的超氧化物歧化酶。结果提示，高血压大鼠Kv 1.5蛋白表达减少，Kv电流降低，细胞去极化。这些改变可能通过产生氧化应激而改变内皮功能。3）细胞内血管紧张素II（angII）刺激动脉平滑肌的电压操纵性钙电流（VOCC）。血管紧张素II 1型受体、G蛋白、磷脂酶C或C激酶的阻断剂抑制细胞内血管紧张素II的刺激作用。结果表明，细胞内血管紧张素II结合到1型受体样结合位点内的细胞，激活G-蛋白，磷脂酶C和蛋白激酶C，并增强VOCC动脉平滑肌细胞。少

Our progress during two years (2001-2002) are summarized as follows:1) Decreased voltage-dependent potassium (Kv) currents in arterial smooth muscle cells from stroke-prone spontaneously hypertensive rats(SHR-SP)Amplitudes of Kv currents were decreased in arterial muscle cells from SHR-SP, compared to those from normotensive control, Wistar Kyoto rats (WKY) by the use of patch clamp experiment. Antihypertensive treatment to SHR-SP with angiotensin II receptor blocker normalized the current alteration in part, and young rats did not have such alteration. Pharmacological evaluation showed that 4-aminopyridine sensitive potassium currents were decreased in SHR-SP. Quantitative RT-PCR showed that expression of Kv2.1 mRNA, was decreased among various Kv proteins. Results suggest that the sustained hypertension and/or stimulation of renin-angiotensin system alters the Kv channels.2) Decreased Kv currents in endothelial cells from aorta of SHR-SP.4-aminopyridine sensitive Kv currents were dec … More reased in endothelial cells from the aorta of SHR-SP, compared with WKY. Resting membrane potential in endothelia cells from SHR-SP was more depolarized than those from WKY. By the use of the antibodies for various Kv proteins, the staining of Kv1.5 in endothelial cells was decreased in SHR-SP. In the tension recording of the aorta, an application of 4-amynopyridine impaired the endothelium dependent relaxation, which was partially restored by a pretreatment of superoxide dismutase. Results suggest that the expression of Kv1.5 protein is decreased in hypertensive rats, which in turn decreases Kv current and depolarizes the cell. These alterations may contribute to the altered endothelial function by producing oxidative stress.3) Intracellular angiotensin II (ang II) stimulates voltage-operated calcium currents (VOCC) in arterial smooth muscle.Intracellular application of ang II stimulated VOCC. Blockers for either ang II type 1 receptor, G-protein, phospholipase C, or C-kinase inhibited the stimulating action of intracellular ang II. Results suggest that intracellular ang II binds to the type 1 receptor-like binding sites inside the cell, activates G-protein, phospholipase C, and protein kinase C, and enhances VOCC in arterial smooth muscle cells. Less