ANION-EXCHANGER AE1 AS A CANDIDATE PATHWAY FOR TAURINE TRANSPORT IN RAT ERYTHROCYTES

Taurine has been shown to act as an osmolyte during the regulatory vol ume decrease process in a variety of cell types. The nature of the tau rine efflux carrier is thought to consist of a diffusional pathway wit h pharmacological properties similar to a chloride channel or through an anion exchanger. We propose that taurine is a substrate of the anio n exchanger AE1, also called band 3. Experiments were performed in rat erythrocytes, which express large amounts of band 3. Taurine uptake a nd efflux transport experiments were determined in the presence of inh ibitors of anion carriers and chloride channels. Both taurine uptake a nd efflux were inhibited by band 3 inhibitors 4,4'-diisothiocyanostilb ene-2,2'-disulfonic acid (DIDS), 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS), niflumic acid, or furosemide. Moreover, DIDS competes wit h taurine at a common binding site in the uptake process. Specific inh ibitors of the electroneutral cotransport as well as inhibitors of the chloride channels were ineffective in blocking taurine transport. Thu s we suggest that band 3 may be the protein responsible for taurine tr ansport in rat erythrocytes.