OSMOTIC SWELLING OF HEPATOCYTES INCREASES MEMBRANE CONDUCTANCE BUT NOT MEMBRANE CAPACITANCE

We have used the whole-cell patch-clamp technique to study changes in membrane conductance and membrane capacitance after osmotic swelling i n rat hepatocytes. Hypoosmotic solutions induced an instantaneous incr ease in the volume of patch-clamped cells that was followed by a slow decline reminiscent of regulatory volume decrease as seen in intact ce lls. These morphological changes were associated with a transient incr ease in membrane conductance. The rise in conductance was not correlat ed with changes in capacitance, neither in time after the initiation o f cell swelling nor in magnitude. Therefore we conclude that an osmoti cally induced increase in conductance is probably a result of the acti vation of existent channels in the plasmalemma and not a result of the fusion of vesicle membrane containing ionic channels.