Zou A P, Fleming J T, Falck J R, Jacobs E R, Gebremedhin D, Harder D R, Roman R J
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226, USA.
Am J Physiol. 1996 Jan;270(1 Pt 2):R228-37. doi: 10.1152/ajpregu.1996.270.1.R228.
The present study examined the effects of 20-hydroxyeicosatetraenoic acid (20-HETE) and 17-octadecynoic acid (17-ODYA), an inhibitor of the metabolism of arachidonic acid by P-450, on K(+)-channel activity in vascular smooth muscle cells (VSM) isolated from renal arterioles of the rat. Two types of K+ channels were characterized using inside-out excised membrane patches. One channel exhibited a large conductance (250.3 +/- 5 pS), was activated by membrane depolarization and elevations in cytoplasmic Ca2+ concentration, and was blocked by low concentrations (< 1 mM) of tetraethylammonium (TEA). The other K+ channel exhibited an intermediate conductance (46.3 +/- pS), was activated by membrane depolarization but not by changes in intracellular Ca2+ concentration, and was blocked by 4-aminopyridine (5 mM). Addition of 20-HETE to the bath (1-100 nM), reduced the frequency of opening of the large-conductance Ca(2+)-activated K+ channel recorded using cell-attached patches on VSM. It had no effect on the intermediate-conductance K+ channel: 17-ODYA (1 microM) increased the activity of the large-conductance Ca(2+)-activated K+ channel, and this effect was reversed by 20-HETE (10 nM). 20-HETE (1-1000 nM) reduced the diameter of isolated perfused small renal arteries of the rat by approximately 15% TEA (1 mM) blocked the vasoconstrictor response to 20-HETE (100 nM). These studies suggest that 20-HETE is an endogenously formed vasoconstrictor that acts in part by inhibiting the opening of the large-conductance Ca(2+)-activated K+ channel in renal arteriolar VSM.
本研究检测了20-羟基二十碳四烯酸（20-HETE）和17-十八炔酸（17-ODYA，一种细胞色素P-450介导的花生四烯酸代谢抑制剂）对从大鼠肾小动脉分离的血管平滑肌细胞（VSM）中钾通道活性的影响。采用内面向外式膜片钳技术对两种类型的钾通道进行了特性分析。一种通道表现出大电导（250.3±5 pS），被膜去极化和胞质钙离子浓度升高激活，并被低浓度（<1 mM）的四乙铵（TEA）阻断。另一种钾通道表现出中等电导（46.3± pS），被膜去极化激活，但不受细胞内钙离子浓度变化的影响，并被4-氨基吡啶（5 mM）阻断。向浴槽中加入20-HETE（1-100 nM），可降低用VSM上的细胞贴附式膜片钳记录的大电导钙激活钾通道的开放频率。它对中等电导钾通道没有影响：17-ODYA（1 μM）增加了大电导钙激活钾通道的活性，而20-HETE（10 nM）可逆转这种作用。20-HETE（1-1000 nM）使大鼠离体灌注小肾动脉的直径减小约15%，TEA（1 mM）可阻断对20-HETE（100 nM）的血管收缩反应。这些研究表明，20-HETE是一种内源性血管收缩剂，其部分作用机制是抑制肾小动脉VSM中大电导钙激活钾通道的开放。
