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

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Abstract
Washed human erythrocytes were incubated in phosphate-buffered saline at 37 oC with different concentrations (2-80 mgl-1) of the monovalent cationo-phore 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 10mgl-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 5mgl_1 (to avoid haemolysis) lead to a similar effect on the energy status. Ouabain at 0.5mmoir' 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.