一氧化氮和硫化氢对大鼠结肠平滑肌钙钾电流影响的比较

Comparison of the effects of nitric oxide and hydrogen sulfide on calcium and potassium currents of rat colonic smooth muscle

目的比较一氧化氮（NO）与硫化氢（H2S）对大鼠结肠平滑肌细胞钙钾电流的影响，并探讨其抑制结肠动力的机制。方法采用酶消化法分离近端结肠平滑肌细胞，运用全细胞膜片钳技术记录NO供体硝普钠（SNP，200μmol／L）和H2S供体硫氢化钠（NaHS，300μmol／L）对平滑肌细胞L型钙通道电流（ICa，L）和大电导钙激活钾电流（IBK。）的影响。结果膜电位0mV处，SNP和NaHS均显著抑制ICa,L峰值，SNP使峰电流密度由[（-3．76±0．66）pA／pF]降低至[（～2．67±0．42）pA／pF]（P〈0．01）；NailS使峰电流密度由[（-4．13±0．29）pA／pF]降低至[（-2．73±0．76）pA／pF]（P〈0．01）；SNP明显抑制L型钙通道I—V曲线，但不影响其电压依赖特性；而NaHS使L型钙通道I～V曲线右移；SNP不影响L型钙通道的激活和失活特性；NariS使L型钙通道的激活曲线和失活曲线均显著右移（P〈0．05）；SNP促进IBKc。，使电流密度由[（12．7±1．9）pA／pF]增加至[（14．7±2．1）pA／pF]（P〈0．05）；NaHS抑制IBKca，电流密度由[（15．5±2．4）pA／pF]降低至[（12．4±2．9）pA／pF]（P〈0．05）。结论NO和H2S均抑制大鼠结肠平滑肌细胞（SMCs）收缩，但两者作用机制不同，NO通过抑制L型钙通道，激活BKCa通道抑制平滑肌收缩，而H2S则通过抑制L型钙通道抑制平滑肌收缩，但同时也抑制BKCa通道，其可能参与平滑肌钙稳态的调节。

Objective To investigate and compare the effects of nitric oxide （NO） and hydrogen sulfide （H2S） on calcium and potassium currents of rat colonic smooth muscle cells （SMCs）. Methods The whole - cell patch - clamp technique was used to record the currents Of L - type calcium channels and large conductance Ca2 - activated KCa （BKca） channels in SMCs isolated from male Wistar rat. Results Both the NO donor Sodium nitroferricyanide （ 11I ） dihydrate （SNP, 200 μmol/L） and the H2S donor NariS （ 300 μmol/L） inhibited L - type calcium current （ Ica L ） at membrane potential of 0 mV, after application of SNP and NariS, the current density significantly reduced from [ （ -3.76 ± 0. 66） pA/pF ] and [ （ -4. 13 ±0.29） pA/pF] to[ （ -2.67 ±0.42） pA/pF]and[ （ -2.73 ±0.76） pA/pF], respective- ly （P 〈 0.05）. SNP had no effect on the voltage - dependent property of Ica＇ L, While the ｜ - V relation- ship of L - type calcium channels was modified by NariS, the peak of I - V curve was shifted to right. SNP did not affect the curves of the steady - state activation, but evoked a leftward shift of the steady - state in- activation curve. However, NariS evoked a significant rightward shift of the steady - state activation curve and inhibited the inactivation of L - type calcium channels （P 〈O. 05）. BKca channel currents were signif- icantly increased by SNP, the current density was increased from [ （ 12.7 ± 1.9） pA/pF] to[ （ 14. 7 ±2.1） pA/pF] （P〈0.05）; while inhibited by Naris （control[ （15.5±2.4） pA/pF] vs. Naris [ （ 12. 4 ± 2.9） pA/pF] （P 〈 0. 05 ）. Conclusion Both NO and H2 S inhibit the contraction of colonic SMCs, while the mechanisms are different. The relaxant effect of NO on rat colonic muscle is due to direct inhibition of L type calcium channels and activation of BKca channels. The relaxant effect of H2 S on colonic muscle may be associated with the direct inhibition of H：S on L- type calcium channels. H2S may involve in the regulation of calcium homeostasis in colonic SMCs of rat colon.