Enzymes activated by monovalent cations

Effects of valinomycin, ouabain, and potassium on glycolysis and intracellular pH of Ehrlich ascites tumor cells

Both valinomycin and ouabain block reaccumulation of K(+) by Ehrlich ascites tumor cells depleted of K(+) and cause loss of K(+) from high-K(+) cells. Glucose largely reverses the effect of valinomycin and to a lesser extent that of ouabain.In cells depleted of K(+), glucose utilization and lactate production are impaired. Neither extracellular pH (pHe) nor intracellular pH (pHi) falls to the extent seen in non-depleted glycolyzing cells. Addition of K(+) to depleted cells reverses these effects. Valinomycin increases glycolysis in K(+)-depleted cells but to a greater extent in nondepleted or K(+)-repleted cells. The increase in lactate production caused by valinomycin is accompanied by a correspondingly greater fall in pHe and pHi. Valinomycin, unlike other uncoupling agents, does not abolish the pH gradient across the plasma membrane. Increased utilization of glucose resulting from addition of K(+) to K(+)-depleted cells or addition of valinomycin either to depleted or non-depleted cells can be entirely accounted for by increased lactate production. Ouabain blocks the stimulatory effect of added K(+) on K(+)-depleted cells and has an inhibitory effect on glycolysis in non-depleted cells. It does not obliterate the difference in glycolytic activity between K(+)-depleted and nondepleted cells. Ouabain does not completely block the effect of valinomycin in augmenting glycolysis in depleted or non-depleted cells. Increased accumulation of glycolytic intermediates, particularly dihydroxyacetone phosphate, is found in glycolyzing K(+)-depleted cells. The most marked accumulation was found in ouabain-treated K(+)-deficient cells.