Datensatz

Zusammenfassung

Dansylation of the red blood cell membrane inhibits monovalent anion transport as measured by means of ³⁶Cl and enhances divalent anion transport as measured by means of ³⁵SO₄ (Legrum, Fasold and Passow (1980) Hoppe-Seyler's Z. Physiol. Chem. 361, 1573–1590 and Lepke and Passow (1982) J. Physiol. (London) 328, 27–48). In the present work the effect of densylation on phosphate equilibrium exchange was studied over the pH range where the ratio between monovalent and divalent phosphate anions varies. At high pH, phosphate equilibrium exchange was enhanced; at low pH, exchange was inhibited. The pH maximum of phosphate equilibrium exchange, seen at pH 6.3 in untreated ghosts is now replaced by a plateau. The inverse effects of dansylation on the rates of exchange at high and low pH suggest that both monovalent and divalent phosphate anions are accepted as substrates by the anion transport protein. A tentative attempt to obtain a quantitative estimate of the ratio of monovalent and divalent phosphate transport indicates that in the untreated red cell membrane over the pH range 7.2–8.5 the transport of HPO₄²⁻ is negligible compared to the transport of H₂PO₄⁻.