有氧运动对大鼠脑动脉平滑肌细胞BK_(Ca)通道生物物理特性的影响

Aerobic Exercise Changes the Biophysical Properties of BK_(Ca) Channels in Cerebral Arterial Smooth Muscle Cells in Rats

目的:观察有氧运动对大鼠脑动脉平滑肌细胞(SMC)的大电导钙激活钾通道(BKCa)生物物理特性的影响,为运动有效预防脑血管疾病的细胞学机制提供实验依据。方法:8周龄雄性Wistar大鼠20只,随机分为两组,安静对照组(SED)和运动组(EX)。运动组进行12周跑台运动(20 m/min,60 min/d,5 d/w)。12周后,取脑动脉,经酶消化法获得单个脑动脉SMC。采用膜片钳单通道内面向外记录模式,观察各组BKCa通道的生物物理特性。结果:1)本实验中BKCa的单通道电导为221.8±6.1p S(n=8),记录电流反转电位接近0 m V,无整流现象,均符合BKCa单通道特征;2)12周有氧运动使BKCa通道活性提高:钳制电位+40 m V,[Ca2+]i为1μM时,SED和EX组BKCa通道平均开放概率分别为0.28±0.02和0.78±0.07 p S 3)有氧运动使BKCa通道电压依赖性增强:[Ca2+]i为1μM时,SED和EX组开放概率-电压曲线左移,V1/2分别为48.09±3.27 m V和26.57±3.17 m V;4)有氧运动使BKCa通道钙敏感性增强:膜电位+40 m V下,SED和EX组Po-[Ca2+]i曲线左移,Kd值分别为2.80±0.09μM和0.35±0.09μM;5)运动组大鼠BKCa通道平均开放时间(To)增大,平均关闭时间(Tc)缩短,开放时间常数(τO)增大,关闭时间常数(τC)减小,提示有氧运动使通道更易开放且更难关闭。结论:长期规律性有氧运动能改变大鼠SMC的BKCa通道门控特性,使其活性增强,这可能是运动改善脑血管舒缩功能,增强脑动脉供血的重要机制之一。

Objective The present study investigated the effects of aerobic exercise on the biophysical properties of Ca2＋-activated K＋（BKCa）channel in cerebral arterial smooth muscle cells（SMCs）of rats. Methods Twenty 8-week-old male Wistar rats were randomly assigned into two groups：sedentary control group（SED）and exersice group（EX）. Rats in group EX underwent 12-week treadmill exercise60 min per day,5 days per week at the speed of 20m/min. Thereafter,the cerebral arteries of the rats in the two groups were removed,and the arterial SMCs were obtained using enzymatic isolation method. The biophysical properties of BKCawere examined using inside-out patch clamp recording technique. Result（1）The conductance of single BKCachannel was 221.8 ± 6.1p S（n = 8）and reversal potensial was approached to 0 m V,which met the feature of single BKCachannel.（2）The activity of BKCachannel in SMCs significantly increased in group EX when command potential=＋40m V and [Ca2＋]i=1μM. The open probability（Po）of BKCachannel in group EX（0.78 ± 0.07）was significantly higher that than in group SED（0.28 ± 0.02）.（3）The Po of voltage curve shifted to left,and the V1/2value in SED and EX group was 48.09 ± 3.27 m V and 26.57 ± 3.17 m V,respectively,when [Ca2 ＋]i=1μM.（4）The Po-[Ca2 ＋]icurves shifted to the left,and the Kd value in groups SED and EX was 2.80 ± 0.09 μM and 0.35 ± 0.09 μM,respectively.（5）The channel mean opening time and opening time constant increased significantly,and the channel mean closing time and closing time constant decreased significantly in group EX.Conclusion Regular aerobic exercise alters the biophysical properties of BKCachannel in cerebral arterial myocytes and increase the channel activity of rats,which probably causes the vascular dilation and improves blood flow in brain.