去甲肾上腺素对一氧化氮在小鼠十二指肠肌条收缩中作用的影响机制

Effect of noradrenaline on nitric oxide action in the contraction of mouse duodenal muscle strips

目的:观察一氧化氮(nitric oxide,NO)对离体小鼠十二指肠肌条收缩幅度及去甲肾上腺素(noradrenaline,NA)对NO作用的影响;探讨NA和NO之间的关系及影响机制. 方法:将分离的小鼠十二指肠肌标本置于10 mL 37±1℃新鲜配置的Krebs液的浴槽中,从浴槽底部持续通入950 mL/LCO2和50 mL/LO2的混合气体.通过张力换能器记录张力变化,观察NO对十二指肠肌条收缩幅度及NA对No作用的影响,用多种拮抗剂或抑制剂左旋-硝基精氨酸(L-NNA)、酚妥拉明、ODQ探讨NA 与NO之间的关系. 结果:L-Arg对肌条的收缩幅度有明显的抑制作用, 在浓度2×10-2-2×10-6mol/L范围内呈剂量-效应关系.除2×10-6mol/L组外,其余各浓度的L-Arg与对照组均有显著性差异(P<0.001).NA对肌条的收缩幅度有明显的抑制作用,在浓度1.2×10-4-1.2×10-8mol/L范围内呈剂量-效应关系.除1.2×10-8mol/L组外,其余各浓度的NA与对照组均有显著性差异(P<0.001).用无反应剂量1.2×10-8mol/L的NA孵育标本后加入浓度为2×10-3,2×10-4,2×10-5,2×10-6mol/L 的L-Arg对肌条收缩幅度的抑制作用明显增强,与单独L-Arg组的作用相比差异有显著性(P<0.001);而2×10-2mol/L L-Arg组与单独L-Arg组的作用相比差异无显著性.用1.2×10-6mol/LNA孵育标本后加入L-Arg, 各浓度的L-Arg与单独L-Arg组相比差别有显著性(P<0.001).分别用一氧化氮合酶(NOS)的抑制剂L- NNA,可溶性鸟苷酸环化酶(sGC)抑制剂ODQ,α肾上腺素能受体阻断剂酚妥拉明均使NO对肌条收缩幅度抑制效应明显减弱,与对照组比较有显著性差异(P<0.001). 结论:L-Arg经NOS催化生成NO,NO与sGC结合, 激活了NO的下游途径,从而抑制了十二指肠肌收缩. 而NA可以增强NO的抑制效应,可能是通过α受体直接或间接影响了NOS的活性或者NO受体后机制.

AIM: To investigate the effect of nitric oxide (NO) on the contraction of isolated mouse duodenal muscle strip (DMS), and the influence of noradrenaline (NA) on the action of NO. METHODS: DMS isolated from mice were suspended in tissue chambers containing Krebs solution (10 mL, 37±1 ℃), with a continuing supply of gas mixture (950 mL/LCO2, 50 mL/LO2) from the bottom. L-Arg was used to produce NO. Contraction of DMS in the presence of NO and NA was recorded with tension transducer. ODQ (inhibitor of sGC), L-NNA (general inhibitor of NOS), and phentolamine (blocker of a adrenergic receptor) were used to explore the relationship between NO and NA. RESULTS: L-Arg at concentrations from 2×10-5 to 2×10-2 mol/L decreased the DMS contractile amplitude in a dose-dependent manner (P<0.001). No significant effect was observed when L-Arg was used at the concentration of 2×10-6 mol/L. Similarly, NA dose-dependently decreased the DMS contractile amplitude at concentrations ranging from 1.2×10-7 to 1.2×10-4 mol/L (P<0.001), but no significant effect was noted at 2×10-8 mol/L. At 1.2×10-8 mol/L, NA increased the effect of L-Arg at concentrations from 2×10-6 to 2×10-3 mol/L on the contraction of DMS (P<0.001); Furthermore, at 1.2×10-6 mol/L, NA enhanced the effect L-Arg at all concentrations from 2×10-6 to×10-2 mol/L (P<0.001). This effect of L-Arg was inhibited by L-NNA, ODQ and phentola-mine(P<0.001). CONCLUSION: NO can inhibit the contraction of the DMS, which can be synergized by NA through augmenting NO synthase activity or via a post-receptor mechanism.