Voltage-dependent inactivation of volume-regulated Cl- current in human T84 colonic and B-cell myeloma cell lines

The voltage-dependent inactivation of a volume-regulated Cl- current (VRChlC) in an epithelial (T84), and a B cell myeloma (RPMI-8226) cell lines were compared. Both cell types exhibited similar time and voltage-dependent current inactivation when recorded using standard whole cell patch technique, with a NaCl external solution that was approximately 90 mOsm hypotonic to the Cs-Glutamate internal solution. The time course of voltage-dependent current inactivation was fit by the sum of a slow, dominant voltage-dependent and a faster voltage-independent components. Recovery from inactivation was approximated by a single exponential process and was dependent on the recovery voltage. The major difference was that the voltage-dependent current inactivation in myeloma cells was shifted to a approximately 30mV more depolarized value than that in T84 cells although the effective charge movement of inactivation was similar. These results indicate that the macroscopic volume-regulated Cl- current in these two cell lines is functionally similar.