肠系膜动脉阻力血管平滑肌钙离子单通道特性及硝普钠的作用

Characteristics of the single calcium channel of resistance vessel in mesenteric artery and the effect of sodium nitroprusside

目的腹部血流在维持消化系统和循环系统的稳态中发挥重要作用,其中肠系膜动脉阻力血管起关键作用。我们应用膜片箝技术,研究Wistar大鼠肠系膜动脉阻力血管平滑肌钙离子单通道特性及硝普钠对其影响。方法从Wistar大鼠肠系膜动脉分支阻力血管分离新鲜平滑肌细胞。以100mmol·LBa~为载流子应用细胞贴附式(cell attached)膜片箝方法,记录细胞膜钙离子单通道电流(I_(Ca))。箝制电压为-70mV,检测电压分别为10mV和+20mV。结果此(I_(Ca))的平均电流幅值(A)开放时和开放概率(Po)分别为(平均数标准差10):在检测电压10mV时;A(1.16±0.28)pA,(1.7±0.82)ms和Po(0.16±0.09);检测电压+20mV时:A(1.14±0.34)pA,(1.5+0.76)ms和Po(0.20±0.10)。Bay K 8644(L型钙通道的激动剂)可激活I_(Ca)将一氧化氮(NO)供体硝普钠(10~9mol·L^1)加入细胞浴液,数秒之内I_(Ca)活动即被灭活或抑制,并于数分钟内恢复,有时在对I_(Ca)的抑制作用之后可记录到兴奋作用,此时如再次应用同样剂量的硝普钠I_(Ca)活动可再被抑制。结论 NO可灭活肠系膜动脉A_4A_5段阻力血管平滑肌细胞膜I_(Ca)随后所产生的兴奋作用,可能由NO的代谢产物所致,这是首次在同一膜片记录到NO双向和的报道。

AIM To study the characteristics of the single calcium channel of resistance vessel in mesenteric artery and the effect of sodium nitroprusside with patch clamp technique. METHODS Fresh cells of resistance vascular smooth muscle were dissociated from A_4 A_5 branches in mesenteric artery of Wistar rats. The single calcium channel currents (I_(Ca)) were recorded from the cellular membrane in cell-attached configuration using the 100 mmoI·L^1 Ba^2 as carrier. The holding potential was 70mV and test potential was +10 and +20mV respectively. RESULTS The average amplitudes. open time and open probability of I_(Ca) were 1.16+0.28pA, 1.7±0.82ms and 0.16±0.09 and 1.14+0.34pA, 1.5+0.76ms and 0.20+0.10 (x's, n-10)in 10 and 20mV test potential respectively. The I_(Ca) could be activated by Bay K 8644 (an agonist of L-type calcium channel). In the most cases, the I_(Ca) could be inactivated within a few seconds by adding sodium nitroprusside ( 10~9 moI·L^1, a donor of NO) in the bath solution, which could be recovered within a few minutes. Some times an exciting effect could be recorded following the down regulation of ICa. If the SNP was applied again at a same dose, the activity could be inhibited again. CONCLUSION The I_(Ca) of resistance vascular smooth muscle cellular membrane from A_4-A_5 branches in mesenteric artery could be inactivated by NO. The active effect on I_(Ca) following the inhibitory effect of NO could be induced by the metabolic material of NO.