Modulation by extracellular and intracellular iodide of volume-activated Cl^– current in HeLa cells

Abstract

 The patch-clamp technique was used to study the effect of extracellular and intracellular iodide on the properties of the volume-activated anion current in HeLa cells. Upon hypotonic challenge, HeLa cells responded by activating an outwardly rectifying Cl^– current. Replacement of extracellular Cl^– by I^–, a more permeable anion, increased the peak outward and inward current, reduced the magnitude of deactivation observed at depolarized potentials and shifted the half-maximal (V_0.5) deactivation voltage towards more positive values. On the other hand, when internal Cl^– was replaced by I^– the volume-activated current was not observed in normal, Cl^–-rich hypotonic extracellular solution. However, switching to a hypotonic extracellular solution containing a mixture of Cl^– and I^– resulted in the activation of the volume-sensitive current. Furthermore, once the current was activated, I^– could be excluded from the external solution without significantly affecting the current properties. These results suggest that the permeant anion plays a crucial role in the gating mechanism of the volume-activated Cl^– current, influencing the swelling-dependent activation and the voltage-dependent deactivation processes.