Inhibition of volume regulation and efflux of osmoregulatory amino acids by blockers of Cl- transport in cultured astrocytes.

Regulatory volume decrease (RVD) in astrocytes was inhibited by the Cl- exchanger blockers 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), dipyridamole and niflumic acid but not by the Cl- channel inhibitors diphenylamine-2-carboxylate (DPC) and anthracene-9-carboxylate (9-AC). The volume activated efflux of [3H]taurine and [3H]D-aspartate (as marker for glutamate) was similarly affected by these compounds. However, neither RVD nor osmolyte fluxes were significantly reduced by removal of external Cl-, suggesting that an anion exchanger activity is not required for the volume regulatory process. Alternatively, these results suggest that the anion exchanger molecule may function as an unidirectional Cl- channel possibly permeable also to amino acids.