Simultaneous recording of cell volume, membrane current and membrane potential: effect of hypotonic shock.

Using the slow whole-cell recording technique (Horn & Marty 1988), we measured the change of membrane current and potential induced by a hypotonic shock, while simultaneously monitoring the cell size. A transient depolarization could be measured which was accompanied by a transient change of the membrane current. The maximal cell size was reached before the depolarization and the current adopted their maximal values. Volume regulatory decrease could also be observed in Ca2(+)-free hypotonic bath solutions, but the time course of cell shrinking as well as the change of membrane current and potential was slowed down. In contrast, a regulatory volume decrease could not be observed in whole-cell records and the cell size steadily increased. The data show that the slow whole-cell recording technique is suitable for analysis of ion transport systems involved in volume regulation.