Effects of the ionophore gramicidin D on energy metabolism in human erythrocytes.

Washed human erythrocytes were incubated in phosphate-buffered saline at 37 degrees C with different concentrations (2-80 mg l-1) of the monovalent cationophore gramicidin D. The ionophore induced a decrease of ATP content and energy charge (EC) and a concomitant increase in ADP and AMP contents. At a concentration of 10 mg l-1 of the ionophore the reduction of EC and ATP concentration was about 50%. Increasing the concentration of the ionophore resulted in a substantial haemolysis with no further effect on the nucleotide levels. Lowering the concentration of the ionophore to 5 mg l-1 (to avoid haemolysis) lead to a similar effect on the energy status. Ouabain at 0.5 mmol l-1 in incubation medium distinctly blunted the ionophoric effect on EC and adenine nucleotides. Addition of glucose on the contrary reversed these effects by about 80%. Hence, the glucose-induced increase in glycolytic flux as evidenced by an increase in lactate production was not sufficient to restore energy state.