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

Abstract

The effects of phloretin, H₂DIDS (4,4′‐diisothiocyano‐1,2‐diphenylethane‐2,2′‐disulfonate) and SO₄⁻² on anion transport in Ehrlich ascites tumor cells was studied in an effort to determine whether Cl⁻ and SO₄⁻² share a common transport mechanism. Sulfate, in the presence of constant extracellular Cl⁻ (100 mM), reduces Cl⁻ self‐exchange by 43% (40 mM SO₄⁻²) and Cl⁻−SO₄⁻² exchange by 36% (25 mM Cl⁻/O SO₄⁻²) compared to 25 mM Cl⁻/50 mM SO₄⁻². Phloretin blocks without delay and to the same extent the self‐exchange of both Cl⁻ and SO₄⁻². For example, at 10⁻⁴ M phloretin, anion transport is inhibited 28% which increases to 78% at 5 × 10⁻⁴ M. Reversibly bound H₂DIDS also inhibits the self‐exchange of both Cl⁻ and SO₄⁻². However, at all H₂DIDS concentrations tested (0.5 − 10 × 10⁻⁵ M) SO₄⁻² transport was far more susceptible to inhibition than that of Cl⁻. H₂DIDS when irreversibly bound to the cell inhibits SO₄⁻² but not Cl⁻ transportThe results of these experiments are consistent with the postulation that both Cl⁻ and SO₄⁻² are transported by a common mechanism possessing two reactive sites.