The Interaction of Chloride with the Sulfate Transport System of Ehrlich Ascites Tumor Cells

The effect of Cl- on SO4(-2) efflux was studied in both Cl--containing and Cl--free ascites tumor cells loaded with 35SO4(-2) to test the hypothesis that Cl--SO4(-2) exchange is mediated by the same mechanism responsible for SO4(-2)-self exchange. The addition of Cl--free, 35SO4(-2) loaded cells to a SO4(-2)-free, Cl- medium results in: (1) SO4(-2) efflux that is dependent on the extracellular Cl- concentration (Km = 4.85 mM; ke = 0.048 min-1 at 50 mM Cl-) and (2) net Cl--uptake that exceeds SO4(-2) loss. Both SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate) and ANS (1-anilino-8-napthalene sulfonate) inhibit S04(-2) efflux but are without effect on Cl- uptake. The addition of Cl--containing, 35SO4(-2) loaded cells to a SO4(-2)-free, Cl- medium results in: (1) a slight gain in cellular Cl- and (2) ke for SO4(-2) efflux identical to that for Cl--free cells.