Binding of oxpentifylline to the erythrocyte membrane and effects on cell ATP,cation content,and membrane area

Abstract

Erythrocyte ATP was partially depleted by incubating normal human erythrocytes at 37°C for 24 hours. Incubation in the presence of 5 mmol/l oxpentifylline caused further depletion of ATP irrespective of whether membrane Na⁺/K⁺ pump or Na⁺/K⁺/Cl⁻ cotransport activities were inhibited and whether glycolysis was stimulated or inhibited. Similar depletion of erythrocyte ATP was found by incubating erythrocytes with either metabolite I of oxpentifylline, the rheologically active oxpentifylline analogue A81 3138, or the rheologically inactive natural methylxanthine theophylline. Partitioning of ¹⁴C-oxpentifylline into the erythrocyte membrane was demonstrated but this did not increase membrane surface area as tested by hypotonic stress. Thus the rheological action of oxpentifylline at 37°C, which is associated with inhibition of K⁺ efflux from erythrocytes, is a membrane-associated event and does not involve an increase in cell ATP content.