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 in rat hepatocytes. Hypoosmotic solutions induced an instantaneous increase in the volume of patch-clamped cells that was followed by a slow decline reminiscent of regulatory volume decrease as seen in intact cells. These morphological changes were associated with a transient increase in membrane conductance. The rise in conductance was not correlated with changes in capacitance, neither in time after the initiation of cell swelling nor in magnitude. Therefore we conclude that an osmotically induced increase in conductance is probably a result of the activation of existent channels in the plasmalemma and not a result of the fusion of vesicle membrane containing ionic channels.