一氧化氮对哮喘大鼠支气管平滑肌细胞钾通道的作用

目的　观察一氧化氮 (NO)供体硝普钠 (SNP)作用前、后哮喘大鼠支气管平滑肌细胞(BSMC)静息膜电位和钾电流的改变 ,为阐明NO松弛气道平滑肌的机制提供实验资料。方法　雄性SD大鼠 16只 ,按随机数字表法分为正常对照组和哮喘模型组 ,每组 8只。采用急性酶消化法分离单个BSMC ,用常规全细胞膜片钳技术记录正常对照组和哮喘模型组的静息膜电位 (Em)、钙激活剂钾通道 (BKCa)和电压依赖性钾通道 (Kv)电流 ,以及SNP作用后哮喘模型组Em和两种电流的变化。结果　 ( 1)哮喘模型组BSMC的Em为 ( -2 9± 6)mV(n =12 ) ,正常对照组为 ( -3 5± 6)mV(n =15) ,两组比较差异有显著性 (P <0 0 5) ;SNP作用后哮喘模型组BSMC的Em为 ( -3 8± 7)mV(n =12 ) ,与作用前比较差异有非常显著性 (P <0 0 1) ,与正常对照组比较差异无显著性 (P >0 0 5)。 ( 2 )方波刺激模式下哮喘模型组BKCa电流密度 (IKCa)为 ( 4 4± 17)pA/pF(n =8) ,正常对照组为 ( 73± 2 0 )pA/pF(n =10 ) ,两组比较差异有非常显著性 (P <0 0 1) ,SNP作用后哮喘模型组IkCa为 ( 79± 16)pA/pF(n =10 ) ,与作用前比较差异有非常显著性 (P <0 0 1) ,与正常对照组比较差异无显著性 (P >0 0 5) ;斜坡刺激模式下正常对照组和SNP作用前、后哮喘模型组的IkCa分别为

The effect of nitric oxide on potassium channels of bronchial smooth muscle cells from asthmatic rats

OBJECTIVE: To investigate the effect of nitric oxide (NO) on resting membrane potential (Em) and potassium currents of bronchial smooth muscle cells (BSMC) from asthmatic rat models. METHODS: Sixteen male SD rats were randomly divided into two groups: a control group and an asthmatic model group. Single BSMC was obtained by acute enzyme-digestion separation method. All experiments were conducted in conventional whole-cell configuration of patch clamp technique. Em currents of Ca2+ activated potassium channels (BKCa) and voltage-dependent potassium channel (Kv) of two groups were separately measured, and the changes of The resting Em and potassium currents of BSMC before and after addition of NO donor sodium nitroprusside (SNP) were also measured. RESULTS: (1) The Em of the asthmatic model group [(-29 +/- 6) mV, n = 12] was significantly lower than that of the control group [(-35 +/- 6) mV, n = 15, P < 0.05]; SNP significantly increased Em of the asthmatic model group to [(-38 +/- 7) mV, n = 12, (P < 0.0 1)], there is no significant difference of Em between normal group and that of asthmatic model group after SNP treatment (P > 0.05), which meant that SNP could repolarize BSMC to normal. (2) The mean current density of BKCa from asthmatic model group [(44 +/- 17) pA/pF, n = 8] under pulse protocol was significantly lower than that of the control group [(73 +/- 20) pA/pF, n = 10, P < 0.01], and SNP significantly increased the mean current density of the asthmatic model group to [(79 +/- 16) pA/pF, n = 10, P < 0.01], which was close to control group (P > 0.05); under ramp protocol, the current densities of control and asthmatic model group were [(75 +/- 19) pA/pF, n = 10] and [(46 +/- 16) pA/pF, n = 8] respectively, there was significant difference between two groups (P < 0.01), SNP treatment significantly increased current density of asthmatic model group to [(82 +/- 21) pA/pF, n = 8, P < 0.01]. (3) The mean current density of Kv of the asthmatic model group [(32 +/- 9) pA/pF, n = 8] under pulse protocol was significantly lower than that of the control group [(58 +/- 10) pA/pF, n = 8, P < 0.05], and SNP significantly increased the mean current density of Kv of the asthmatic model group to [(45 +/- 13) pA/pF, n = 8, P < 0.05]. Under ramp protocol, current density of Kv of asthmatic model group was [(38 +/- 11) pA/pF, n = 8], which was significantly lower than that of control group [(62 +/- 14) pA/pF, n = 8, P < 0.05], SNP treatment significantly increased Kv current density of asthmatic model group to [(53 +/- 9) pA/pF, n = 8, P < 0.05]. there was a similar change. CONCLUSIONS: SNP can improve the resting membrane potential of BSMC from rat asthmatic models and increase the potassium channel activity of BSMC, which is impaired in asthma status. The result suggests that potassium channel mediates the relaxation effect of NO on asthmatic airway smooth muscle.