Membrane potentials and sugar transport by ATP-depleted intestinal cells: effect of anion gradients

¹ Department of Radiation Biology and Biophysics, University of Rochester Medical Center, Rochester, New York 14642

Rotenone or dinitrophenol treatment was used to decrease cellular ATP levels in isolated chicken intestinal epithelial cells by over 90% and to produce a cell population in which no steady-state accumulation of 3-O-methylglucose (3-OMG) against a concentration gradient is observed. In the presence of imposed inward-directed Na-anion gradients, these cells accumulate 3-OMG against a concentration gradient. The degree of maximal 3-OMG accumulation and initial influx stimulation in the presence of a given anion or combined Na-anion gradient can be correlated with the magnitude of the diffusion potential as determined by the membrane permeability of the given anion (SCN^– > Cl^– > isethionate^– > SO₄^2–). 3-OMG influx in the presence of a large NaCl gradient is comparable in ATP-depleted and normally energized cells. The slight difference in influx (energized > ATP depleted) is diminished by ouabain, suggesting that energized cells maintain a larger membrane potential (diffusion potential or rheogenic Na⁺-K⁺-ATPase ion pump-generated potential) than the ATP-depleted cells. Although initial rates of 3-OMG uptake into Na⁺-depleted normally energized cells also varies with the anion gradient, these differences disappear with time of incubation in Na⁺ or when cells are preincubated in Na⁺. In this situation, function of a rheogenic Na⁺ pump can establish a membrane potential in contrast to the case with ATP-depleted cells, which have a potential only as long as imposed ion gradients are maintained. All these experiments point to an important role for the electrical membrane potential as a driving force for Na⁺-dependent solute transport systems in both ATP-depleted and normally energized cells.

Submitted on August 16, 1978
Accepted on March 21, 1979