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 inhi bitors diphenylamine-2-carboxylate (DPC) and anthracene-9-carboxylate (9-AC). The volume activated efflux of [H-3]taurine and [H-3]D-asparta te (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 activit y is not required for the volume regulatory process. Alternatively, th ese results suggest that the anion exchanger molecule may function as an unidirectional Cl- channel possibly permeable also to amino acids.