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 μ m ) and 4,4′‐diisothiocyanatostilbene‐2,2′‐disulphonic acid (DIDS; 100 μ m ) on regulatory volume decrease (RVD) were measured. The whole‐cell voltage‐clamp technique was used to characterize ICl swell , 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 H 2 O to 210 mOsmol kg −1 H 2 O. In the presence of tamoxifen (10 μ m ) or DIDS (100 μ m ) RVD was abolished, suggesting a role for the VRAC. A hypotonic solution (230 mOsmol kg −1 H 2 O) evoked ICl swell , an outwardly rectifying current displaying time‐independent activation, which reversed upon return to isotonic conditions. The reversal potential ( E rev ) for ICl swell was −14.7 ± 1.4 mV, similar to the theoretical E rev for a selective Cl − conductance. ICl swell was inhibited in the presence of DIDS (100 μ m ) and tamoxifen (10 μ m ), the DIDS inhibition being voltage dependent. Conclusions:  Osmotic swelling elicits an outwardly rectifying Cl − conductance in CAD cells. The ICl swell 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.