Abstract: Objective Regulatory volume decrease(RVD)is an essential function for animal cells 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 RVDprocess 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× 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,Ahypotonic challenge reversibly induced an increases in cell size,furthermore the RVDprocess could be inhibited by K⁺ channel blocker.Conclusion The results showed that rat ventricular myocyte have a RVDprocess under hypotonic condition and hypotonic challenge could activate a volume-sensitive potassium channels.The primary results indicated that RVDprocess 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.

Key words: whole-cell patch clamp, volume-sensitive K⁺ channel, regulatory volume decrease