Modulation of adriamycin uptake by lonidamine in Ehrlich ascites tumor cells

The effect of Lonidamine, 1-(2,4 dichlorobenzyl)-1-H-indazol-3-carboxylic acid, on the uptake of Adriamycin by Ehrlich ascites tumor cells has been investigated. The uptake of Adriamycin is greatly stimulated by Lonidamine and the increase depends on the energy sources of the cell. In the presence of glucose the intracellular drug content is remarkably lower than that in its absence. This difference lies in the mechanism by which Lonidamine enhances the uptake of Adriamycin. The Adriamycin efflux is via an active transport process and, in the presence of glucose, both aerobic glycolysis and oxidative phosphorylation contribute to ATP synthesis. Although Lonidamine inhibits both these pathways, there is still sufficient ATP to extrude a certain amount of Adriamycin. The elevated intracellular concentration of Adriamycin depends not only on the Lonidamine-inhibited outward transport but also on higher membrane permeability which allows a low concentration of Adriamycin (18 microM) to interfere also with the oxidative metabolism of Ehrlich ascites tumor cells.