Gao Ya-dong, Xiong Sheng-dao, Xu Yong-jian, Zhang Zhen-xiang, Liu Xian-sheng
Department of Respiratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. Wuhan 430030, China.
Zhonghua Jie He He Hu Xi Za Zhi. 2003 Oct;26(10):615-8.
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.
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.
(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.
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.
研究一氧化氮（NO）对哮喘大鼠模型支气管平滑肌细胞（BSMC）静息膜电位（Em）和钾电流的影响。
将16只雄性SD大鼠随机分为两组：对照组和哮喘模型组。采用急性酶消化分离法获取单个BSMC。所有实验均在膜片钳技术的传统全细胞模式下进行。分别测量两组细胞Ca2+激活钾通道（BKCa）和电压依赖性钾通道（Kv）的Em电流，并检测加入NO供体硝普钠（SNP）前后BSMC静息Em和钾电流的变化。
（1）哮喘模型组的Em[（-29±6）mV，n = 12]显著低于对照组[（-35±6）mV，n = 15，P < 0.05]；SNP使哮喘模型组的Em显著升高至[（-38±7）mV，n = 12，（P < 0.01）]，SNP处理后正常组与哮喘模型组的Em无显著差异（P > 0.05），这意味着SNP可使BSMC复极化至正常。（2）在脉冲方案下，哮喘模型组BKCa的平均电流密度[（44±l7）pA/pF，n = 8]显著低于对照组[（73±20）pA/pF，n = 10，P < 0.01]，SNP使哮喘模型组的平均电流密度显著增加至[（79±16）pA/pF，n = 10，P < 0.01]，接近对照组（P > 0.05）；在斜坡方案下，对照组和哮喘模型组的电流密度分别为[（75±19）pA/pF，n = 10]和[（46±16）pA/pF，n = 8]，两组间有显著差异（P < 0.01），SNP处理使哮喘模型组的电流密度显著增加至[（82±21）pA/pF，n = 8，P < 0.01]。（3）在脉冲方案下，哮喘模型组Kv的平均电流密度[（32±9）pA/pF，n = 8]显著低于对照组[（58±10）pA/pF，n = 8，P < 0.05]，SNP使哮喘模型组Kv的平均电流密度显著增加至[（45±13）pA/pF，n = 8，P < 0.05]。在斜坡方案下，哮喘模型组Kv的电流密度为[（38±11）pA/pF，n = 8]，显著低于对照组[（62±14）pA/pF，n = 8，P < 0.05]，SNP处理使哮喘模型组Kv电流密度显著增加至[（53±9）pA/pF，n = 8，P < 0.05]。有类似变化。
SNP可改善哮喘大鼠模型BSMC的静息膜电位，增加哮喘状态下受损的BSMC钾通道活性。结果提示钾通道介导了NO对哮喘气道平滑肌的舒张作用。
