Identification of swelling-activated Cl- current in rabbit cardiac Purkinje cells

The presence and functional role of the swelling-activated Cl- current (I-Cl(swell)) in rabbit cardiac Purkinje cells was examined using patch-clamp methodology. Extracellular hypotonicity (210 or 135 mOsm) activated an outwardly rectifying, time-independent current with a reversal potential close to the calculated Cl- equilibrium potential (E-Cl). The magnitude of this current was related to tonicity of the superfusate. The current was blocked by 0.5 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). These features are comparable to those of I-Cl(swell) found in sinoatrial nodal, atrial, and ventricular myocytes. I-Cl(swell) activation at 210 and 135 mOsm depolarized the resting membrane potential with 6 and 10 mV and shortened the action potential by similar to18 and similar to33%, respectively. DIDS partially reversed I-Cl(swell)-induced action potential changes. We conclude that I-Cl(swell) is present in Purkinje cells and its activation leads to action potential shortening and resting membrane potential depolarization, both of which can promote the development of reentrant arrhythmias