Role of ATP on the initial rate of amino acid uptake in ehrlich ascites cells

Abstract

Incubation with graded doses of rotenone can bring about a graded lowering of the cellular ATP level. Using cells with varying ATP levels, it can be shown that the initial uptake of [ 14C]glycine, before the cellular concentration exceeds that of the medium, is decreased as ATP decreases. Alterations in cellular cations cannot account for the difference in glycine influx. Prolonged exposure of cells to a lowered ATP content increases the exodus of cellular glycine. Valinomycin reduces the steady-state level of glycine uptake, but its effects can to a major extent be overcome by the addition of glucose. At high extracellular K + (70 mM) neither the sum of the Na ++K + gradients, nor the electrochemical potential of Na + provides sufficient energy to account for glycine and 2-aminoisobutyrate accumulation if a 1:1 coupling between Na + and the amino acid occurs.