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

1)卒中易感型自发性高血压大鼠(SHR-SP)动脉平滑肌细胞电压依赖性钾电流(Kv)的降低。采用膜片钳实验，发现SHR-SP的Kv电流幅度低于正常血压对照Wistar京都大鼠(WKY)。SHR-SP经血管紧张素Ⅱ受体阻滞剂降压治疗后，上述改变部分恢复正常，幼年大鼠无此改变。药理评价显示，SHR-SP的4-氨基吡啶敏感性钾电流降低。定量RT-PCR结果显示，Kv2.1在不同Kv蛋白中的表达均呈下降趋势。结果提示，持续的高血压和/或肾素-血管紧张素系统的刺激改变了Kv通道。2)自发性高血压大鼠主动脉内皮细胞的Kv电流降低。4-氨基吡啶敏感的Kv电流是Dec…。与WKY组相比，SHR-SP组大鼠主动脉内皮细胞减少更多。SHR-SP组内皮细胞静息膜电位较WKY组去极化。通过使用不同Kv蛋白的抗体，SHR-SP的内皮细胞中Kv1.5的染色减少。在主动脉张力记录中，应用4-氨基吡啶可损害内皮依赖性的松弛，这种松弛可被超氧化物歧化酶预处理部分恢复。结果提示，高血压大鼠Kv1.5蛋白表达降低，进而降低Kv电流，使细胞去极化。这些改变可能通过产生氧化应激而导致内皮功能改变。3)细胞内血管紧张素II(Ang II)刺激动脉平滑肌电压依赖性钙电流(VOCC)。血管紧张素Ⅱ1型受体、G蛋白、磷脂酶C或C-激酶的阻断剂均可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结合于细胞内的1型受体样结合部位，激活G蛋白、磷脂酶C和蛋白激酶C，并增强动脉平滑肌细胞的VOCC。较少

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