内源性一氧化氮对哮喘大鼠支气管平滑肌细胞钾通道的影响

Effects of endogenous nitric oxide on potassium channels of bronchial smooth muscle cells from asthmatic rats

目的:观察体内应用一氧化氮(NO)前体左旋精氨酸(L-Arg)对哮喘大鼠支气管平滑肌细胞(BSMC) 钾通道电生理特性的影响,为哮喘治疗提供理论基础。方法:雄性SD大鼠,随机分为对照组、哮喘组和哮喘L-Arg (300 mg/kg)治疗组(L-Arg组)。急性酶消化法分离获得大鼠单个BSMC。用常规全细胞膜片钳技术记录3组BSMC 的静息膜电位(Em)、钙激活钾通道(BKCa)电流和电压依赖性钾通道(Kv)电流的差异。结果:(1)哮喘组的静息膜电 位为(-29．4±5.6)mV,显著低于对照组(-34-8±6．2)mV,(P<0．05);L-Arg治疗组的静息膜电位为(-36．1± 6．8)mv,与哮喘组差异显著(P<0．05)。(2)钙激活钾通道电流:+50 mV电压刺激时,方波刺激模式下哮喘组大鼠 BSMC的BECa峰值电流密度[(43．8±16．5)pA／pF,n=8]低于对照组[(72．5±19．9)pA／pF,n=8],(P<0．01);L-Arg 组的BKCa电流密度[(58．7±12．4)pA／pF,n=8]则高于哮喘组(P<0．05)。(3)电压依赖性钾通道电流:+50 mV电 压刺激时,方波刺激模式下哮喘组大鼠BSMC的Kv峰值电流密度为[(32．4±8．7)pA／pF,n=8],显著低于对照组 [(57．7±9．8)pA／pF,n=8](P<0．01);L-Arg组的Kv峰值电流密度[(43．6±7．9)pA／pF,n=8],显著高于哮喘组 [(32．4±8．7)pA／pF,n=8](P<0．05)。结论:体内应用L-Arg可增加钙激活钾通道和电压依赖性钾通道电流,明 显改善哮喘大鼠BSMC的静息膜电位,从而降低气道平滑肌细胞的兴奋性,可能具有抑制气道高反应性的作用。

AIM： To investigate the effects of in vivo application of L- arginine on potassium channels in bronchial smooth muscle cells （BSMC） isolated from asthmatic model rots. METHODS： Male SD rats were randomly divided into control group, asthmatic group and asthmatic rats treated with L- arginine （L- Arg group）. Single BSMCs were obtained by acute enzyme separation method. The resting membrane potential （Em）, Ca^2± - activated K^± channels （BKCa） currents and voltage-dependent K^± channel （Kv） currents in BSMCs were recorded under whole-cell patch clamp technique. RESULTS： （1） The Em of asthmatic group was significantly lower than that in control group （ P 〈 0.05）. In vivo application of L- Arg significantly hyperpolarized BSMCs near to control group （ P 〉 0.05 ）. （2） The peak current density at ± 50 mV of KCa ： IKca in asthmatic group [ （43.8 ± 16.5） pA/pF] was significantly lower than that in normal group [ （72.5 ± 19.9） pA/pF] （ P 〈 0.01）. Treatment with 300 mg/kg L - Arg significantly increased IKca in asthmatic group to （58.7 ± 12.4） pA/pF （ P 〈 0.05）. （3） The peak currents density at ± 50 mV of Kv： IKv in asthmatic group [ （32.4 ± 8.7） pA/pF] was significantly lower than that in control group [ （57.7 ± 9.8） pA/pF] （P〈0.01）. Treatment with L- Arg also significantly increased IKv in asthmatic group to （43.6± 7.9） pA/pF, （P 〈 0.05）. CONCLUSION： Endogenous NO improves Em in asthmatic BSMCs, increases the activities of BK6, channels and Kv channel. These findings implicate that NO may have a potential therapeutically role in airway hypersensitivity.