Possible involvement of a chloride conductance in the transient outward current of whole-cell voltage-clamped ferret ventricular myocytes.

The transient outward current was studied, using the whole-cell patch-clamp technique, in isolated ventricular cells from the ferret heart. In the presence of 4-aminopyridine and cadmium chloride which respectively blocked the Ca-insensitive and the Ca-dependent outward currents, a residual transient outward current was observed in about 30% of the cells tested. This current was suppressed in external hypochloride solution, completely inhibited by SITS (3mM) and reversed at the equilibrium potential for chloride ions. This suggests the presence of a chloride permeability which could contribute to the repolarization phase of the cardiac action potential. [ABSTRACT FROM AUTHOR]