大鼠心肌细胞容积敏感性与钾离子通道的关系

Correlation of Volume-sensitivity with Potassium Channels in Ventricular Myocyte of Rats

目的观察大鼠心肌细胞调节性容积减小(regulatory volume decrease,RVD)过程,研究参与RVD过程的钾离子通道及其亚型。方法采用膜片钳全细胞记录法,记录急性分离的大鼠心肌细胞在低渗刺激下钾离子电流的变化及特征,分析其所属亚型;用细胞容积测定法观察大鼠心肌细胞RVD的过程。结果膜片钳全细胞记录法证实,低渗刺激激活了心肌细胞的K+通道电流,该K+通道电流可被CsCl和格列苯脲所阻断。同时钾离子通道阻断剂可明显阻断大鼠心肌细胞的RVD过程。结论大鼠心肌细胞在低渗溶液作用下具有RVD过程,钾离子通道,尤其ATP敏感性钾离子通道在大鼠心肌细胞RVD过程中可能具有十分重要的作用。

Objective Regulatory volume decrease（RVD） is an essential function for animal ceils because osmotic perturbation is coupled to a variety of physiological and pathological processes, such as cell proliferation, cell differentiation, and apoptosis. In most cells, RVD is accomplished mainly by KCl efflux induced by parallel activation of K^ ＋ and Cl^- channels. This investigation was aimed to observe the RVD process of rat ventricular myocyte and investigate the characteristics of the K^＋ channel which is responsible for RVD and its subtypes. Methods Whole-cell patch clamp technique was used to record volume-sensitive potassium currents of the acute isolated rat ventricular myocyte under hypotonic condition, analyze its subtypes according its electrophysiological properties. The whole cell current activation and recovery was monitored by repetitively applying （ every 15 ） step pulses （ 1-s duration） from - 100 to ＋ 100 mV from a holding potential of - 40 mV to test potentials （in 20 mV increments）. Isolated rat ventricular myocyte images （400 x magnification） were acquired using a digital video-camera mounted on an inverted microscope at short intervals（ 1 -5 min） during the entire experimental protocol for subsequent analysis. Each image was then used for computer tracing of all myocyte edges to calculate myocyte area. Cell dimensions（diameter or width and length） were monitored with two calibrated graticules （one for width and the other for length） in the microscope. Results The electrophysiological results showed that a whole-cell current could be activited by hypotonic solution, then the currents could be blocked by K ^＋ channel blocker CsCl and ATP - sensitive K^＋ channel blocker glibenclamide, A hypotonic challenge reversibly induced an increases in cell size, furthermore the RVD process could be inhibited by K ^＋ channel blocker. Conclusion The results showed that rat ventrieular myoeyte have a RVD process under hypotonic condition and hypotonic challenge could activate a volumesensitive potassium channels. The primary results indicated that RVD process of rat ventricular myocyte is dependent on the activation of K^ ＋ channels especially the ATP-sensitive K ^＋ channels because of its high sensitivity to glibenclamide.