【摘要】 本文旨在研究血管紧张素Ⅱ(angiotensinⅡ,AngⅡ)对人肠系膜动脉平滑肌细胞大电导钙激活钾通道(large conductance calcium-activated potassium channels,BKCa)的影响,探讨AngⅡ在分子水平扩张血管的作用机制。采用单通道膜片钳及全细胞穿孔膜片钳技术观察人肠系膜动脉平滑肌细胞BKCa对AngⅡ的反应性;采用RT-PCR技术确定人肠系膜动脉上AngⅡ受体基因的表达情况。在细胞贴附式膜片下(Vm=+40mV),直接加入AngⅡ(100nmol/L),人肠系膜动脉平滑肌细胞BKCa的活性无明显变化;经AngⅡ1型受体(angiotensinⅡtype 1 receptor,AT1R)特异性阻断剂缬沙坦(10μmol/L)预处理后,再分别加入25、100和250nmol/L的AngⅡ,BKCa的开放概率明显增加,呈现出浓度依赖性。缬沙坦预处理后,当加入100nmol/LAngⅡ时,BKCa的开放概率由0.010±0.003增至0.039±0.015,平均关闭时间由(2729.5±808.6)ms减至(487.7±182.5)ms(n=11,P<0.05),但平均开放时间和电流幅值在给药前后无明显变化。BKCa被AngⅡ(100nmol/L)激活后,再加入AngⅡ2型受体(angiotensinⅡtype 2 receptor,AT2R)特异性阻断剂PD123,319,BKCa的活性受到抑制,开放概率由0.016±0.003减至0.004±0.001(n=5,P<0.05),而通道平均开放时间、平均关闭时间和电流幅值在给药前后均无明显变化。另外,将人肠系膜动脉平滑肌细胞经缬沙坦和PD123,319共同处理后再加入AngⅡ(100nmol/L),BKCa的活性无明显变化。在全细胞穿孔膜片钳下,平滑肌细胞经缬沙坦(10μmol/L)预处理后,在测试的电压范围内,AngⅡ(100nmol/L)对膜电位从60mV到+30mV时BKCa电流密度均无明显影响,而在+40、+50和+60mV时,BKCa电流密度分别从(9.03±2.23)pA/pF、(12.88±2.55)pA/pF和(17.26±2.84)pA/pF增加到(12.47±2.22)pA/pF、(18.71±2.51)pA/pF和(27.21±3.12)pA/pF(n=6,P<0.05)。经RT-PCR证实人肠系膜动脉上有AT1R和AT2R这两种AngⅡ受体基因的表达。上述结果提示,AngⅡ对经缬沙坦预处理的人肠系膜动脉平滑肌细胞BKCa有激活作用,且这种作用由AT2R所介导。更多还原

【Abstract】 The aim of present study was to explore the vasodilatation mechanism of angiotensin II(AngII) at the molecular level by investigating the effect of AngII on large-conductance Ca2+-activated potassium channels(BKCa) in human mesenteric artery smooth muscle cells.The effect of AngII on BK Ca was observed by using patch clamp single channel recording technique and amphotericinperforated whole-cell recording technique.AngII type 1 receptor(AT1R) and AngII type 2 receptor(AT2R) mRNA expression in human mesenteric artery was detected by RT-PCR.In cell-attached patch(Vm = +40 mV),AngII(100 nmol/L) had no significant effect on BK Ca.After pretreatment with Valsartan(a specific inhibitor of AT1R,10μmol/L),25,100 and 250 nmol/LAngII stimulated BK Ca activity significantly in a dose response manner.After pretreatment of Valsartan,AngII(100 nmol/L) enhanced BK Ca open probability(NP O) from 0.010 ± 0.003 to 0.039 ± 0.015,decreased the mean close time(TC) of BK Ca markedly from(2 729.5 ± 808.6) ms to(487.7±182.5) ms(n=11,P<0.05),but AngII had no significant influences on the amplitude(Amp) and the mean open time(TO) of BK Ca.Further PD123,319(a specific inhibitor of AT2R) treatment prevented the stimulatory effect of AngII:PD123,319 decreased the NP O of BK Ca from 0.016 ± 0.003 to 0.004 ± 0.001(n = 5,P < 0.05),but had no significant influences on Amp,T O and T C of BK Ca.In addition,after pretreatment with Valsartan and PD123,319,AngII(100 nmol/L) had no significant effect on BK Ca.In the amphotericin-perforated whole-cell patch-clamp configuration,after pretreatment with Valsartan,the current density of BK Ca at the voltage of 60-+30 mV had no significant changes before and after adding 100 nmol/LAngII,but the current density of BK Ca at the voltage of +40 mV,+50 mV and +60 mV increased significantly after adding 100 nmol/LAngII,from(9.03 ± 2.23) pA/pF,(12.88 ± 2.55) pA/pF and(17.26 ± 2.84) pA/pF to(12.47 ± 2.22) pA/pF,(18.71 ± 2.51) pA/pF and(27.21 ± 3.12) pA/pF(n=6,P<0.05),respectively.Using RT-PCR,the AT 1 R mRNA and AT2R mRNA from isolated human mesenteric artery were detected.So we can draw a conclusion,AngII can stimulate BK Ca activity in human mesenteric artery smooth muscle cells after pretreatment with Valsartan,which is possibly mediated by AT2R.更多还原