A role for the volume regulated anion channel in volume regulation in the murine CNS cell line, CAD

Aim: The role of the volume regulated anion channel (VRAC) in a model CNS neuronal cell line, CAD, was investigated.

Methods: Changes in cell volume following hypotonic challenges were measured using a video-imaging technique. The effect of the Cl− channel antagonists tamoxifen (10 μm) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 μm) on regulatory volume decrease (RVD) were measured. The whole-cell voltage-clamp technique was used to characterize IClswell, the current underlying the VRAC.

Results: Using the video-imaging technique, CAD cells were found to swell and subsequently exhibit RVD when subjected to a sustained hypotonic challenge from 300 mOsmol kg−1 H2O to 210 mOsmol kg−1 H2O. In the presence of tamoxifen (10 μm) or DIDS (100 μm) RVD was abolished, suggesting a role for the VRAC. A hypotonic solution (230 mOsmol kg−1 H2O) evoked IClswell, an outwardly rectifying current displaying time-independent activation, which reversed upon return to isotonic conditions. The reversal potential (Erev) for IClswell was −14.7 ± 1.4 mV, similar to the theoretical Erev for a selective Cl− conductance. IClswell was inhibited in the presence of DIDS (100 μm) and tamoxifen (10 μm), the DIDS inhibition being voltage dependent.

Conclusions: Osmotic swelling elicits an outwardly rectifying Cl− conductance in CAD cells. The IClswell observed in these cells is similar to that observed in other cells, and is likely to provide a pathway for the loss of Cl− which leads to water loss and RVD. As ischaemia, brain trauma, hypoxia and other brain pathologies can cause cell swelling, CAD cells represent a model cell line for the study of neuronal cell volume regulation.