Chloride and sulfate transport in ehrlich ascites tumor cells: Evidence for a common mechanism

The effects of phloretin, H 2 DIDS (4,4′‐diisothiocyano‐1,2‐diphenylethane‐2,2′‐disulfonate) and SO 4 −2 on anion transport in Ehrlich ascites tumor cells was studied in an effort to determine whether Cl − and SO 4 −2 share a common transport mechanism. Sulfate, in the presence of constant extracellular Cl − (100 mM), reduces Cl − self‐exchange by 43% (40 mM SO 4 −2 ) and Cl − −SO 4 −2 exchange by 36% (25 mM Cl − /O SO 4 −2 ) compared to 25 mM Cl − /50 mM SO 4 −2 . Phloretin blocks without delay and to the same extent the self‐exchange of both Cl − and SO 4 −2 . For example, at 10 −4 M phloretin, anion transport is inhibited 28% which increases to 78% at 5 × 10 −4 M. Reversibly bound H 2 DIDS also inhibits the self‐exchange of both Cl − and SO 4 −2 . However, at all H 2 DIDS concentrations tested (0.5 − 10 × 10 −5 M) SO 4 −2 transport was far more susceptible to inhibition than that of Cl − . H 2 DIDS when irreversibly bound to the cell inhibits SO 4 −2 but not Cl − transport The results of these experiments are consistent with the postulation that both Cl − and SO 4 −2 are transported by a common mechanism possessing two reactive sites.