Transport of drugs through human erythrocyte membranes: pH dependence of drug transport through labeled human erythrocytes in the presence of band 3 protein inhibitor.

To reveal the role of the band 3 anion transport protein of the erythrocyte membrane in drug transport through the membrane, the possible effects of inhibitors of anion transport on the permeability of some anionic drugs were examined. The amounts of these drugs that permeated varied markedly with the pH of the outer medium around human erythrocytes that contained the band 3 protein inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS). In the pH range 7.0-8.0, the membrane permeability of drugs through DIDS-treated erythrocytes was affected by a slight pH change (0.2), whereas that through the intact erythrocytes was not pH dependent. These results suggest that the band 3 protein acts not only as a channel for the transport of anions or some anionic drugs but also as protection for the transport system from changes in the pH of the outer medium.