内皮素对大鼠肺动脉平滑肌细胞膜钾通道的影响

目的观察内皮素(ET-1)对大鼠肺动脉平滑肌细胞(PASMCs)膜电压门控钾通道(K_V)的作用。方法用全细胞膜片钳记录方法研究ET-1对膜电位(E_m)、膜电容(C_m)、电压门控钾电流(IK_V)的影响。结果ET-1可引起PASMCs去极化,并抑制IK_V,抑制IK_V时间明显早于其对E_m变化的影响,ET-1对IK_V的影响呈可逆性和浓度依赖性,在有钙的环境中,ET-1对IK_V峰电流的抑制率明显高于无钙时。结论ET-1可浓度依赖性的抑制IK_V,使常氧大鼠PASMCs去极化,且ET-1对IK_V的抑制作用早于对E_m的影响,这些作用不完全依赖于钙的参与,但钙可加强ET-1对IK_V的抑制作用。

Inhibition of voltage-gated K+ current in rat intrapulmonary arterial smooth muscle cells by endothelin-1

AIM: To investigate the role of endothelin-1 (ET-1) in the physiological and pathophysiological regulating mechanisms of voltage-gated K+ current (IKV) inhibition in rat intrapulmonary arterial smooth muscle cells (PASMCs). METHODS: Single PASMCs were obtained with acute enzyme (collagnase plus papain) dispersing method. Using whole cell patch-clamp technique in freshly isolated rat PASMCs, the effect of ET-1 on voltage-gated K+ current was recorded. RESULTS: ET-1 (1 x 10(-9) mol.L-1) and the voltage-dependent K+ (KV)-channel antagonist 4-aminopyridine (4AP), but not the Ca(2+)-activated K(+)-channel antagonist tetraethylammonium (TEA), caused membrane depolarization. The effect of ET-1 on membrane potential persisted in cells in which intracellular Ca2+ was buffered with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA). ET-1 (1 x 10(-9) mol.L-1) caused a significant reversible inhibition of KV current, which began 4.0 s after application of ET-1, was much earlier than the effect of membrane depolarization of PASMCs (15s). ET-1 (1 x 10(-10) to 1 x 10(-7) mol.L-1) caused a concentration-dependent inhibition of K+ current ( mV, from 136 to 40 pA/pF). The percent inhibition was 71% at 1 x 10(-7) mol.L-1 (n = 6). The effect of ET-1 (1 x 10(-9) mol.L-1) on K+ current was weaker under conditions free of Ca2+ than containing Ca2+. At a test potential of mV, free of Ca2+ conditions reduced the maximum inhibitory effect of ET-1 from 71% to 50%. CONCLUSION: ET-1 modulated pulmonary vascular reactivity by depolarizing membrane potential and inhibiting the K+ current of PASMCs. The effect of ET-1 on PASMCs membrane potential and the inhibition of K+ current were independent of Ca2+, but the inhibition of K+ current was much greater under conditions containing Ca2+ than free of Ca2+.