Single channel properties of swellingª²activated chloride channel in cardiac myocytes

    WANG Jun, XU Hongª²Tao, WU Yanª²Hong, SUN Xiª²Qing

    1Department of Aerospace Biodynamics, Fourth Military Medical University, Xi¬ðan 710033, China, 2Cardiovascular Department, General Navy Hospital, Beijing 100037, China, 3Department of Physiology, Capital University of Medical Sciences, Beijing 100054, China

    ¡¾Abstract¡¿ AIM: To characterize the single channel properties of swellingª²activated chloride channel in freshly isolated mouse cardiac myocytes. METHODS: The cardiac myocytes were isolated from mouse hearts and put in a hypotonic solution. Cellª²attached and insideª²out patch clamp methods were employed to recorll the swellingª²activated Cl- channel current (ICl.swell). RESULTS: Under isotonic conditions, no single channel activities were observed in most patches. Hypotonic superfusionª²induced cell swelling resulted in the appearance of active channel. Under symmetrical condition, the current induced by hypotonicity showed outward rectification and an unitary conductance of (38.1¡À2.5)pS. The open probability of the channel was 0.76¡À0.08 at +100 mV in insideª²out patch recordings. The reversal potential (-34.5¡À2.8) mV of the current was close to the calculated equilibrium potential for Cl- (ECl=-38.6 mV). When [Cl-] changed, the reversal potential (Erev) of the current also shifted. The Cl- channel blocker DIDS reversibly inhibited the channel activity when added to the bath solution. CONCLUSION: In mouse cardiac myocytes, swellingª²activated Cl- single channels show outward rectification and sensitivity to disulfonic stilbene blockerDIDS. ......