Thiol-dependent passive K+-Cl- transport in sheep red blood cells. V. Dependence on metabolism

Measurement of ouabain-insensitive K+ efflux and Rb+ influx in low-K+ sheep red blood cells with artificially altered cellular ATP levels revealed that Cl--dependent K+ transport was activated by N-ethylmaleimide (NEM) in cells with ATP concentrations above 0.5 mM. Depletion of ATP by starvation at 37 degrees C either in glucose-free media for 16 h or in 2-deoxy-D-glucose-containing media for 4 h completely abolished the response of K+-Cl-transport to NEM but did not reduce the basal Cl--dependent K+ flux. On repletion of cellular ATP by a second incubation in media containing glucose, inosine, and inorganic phosphate, the NEM-stimulated K+ (Rb+) flux reappeared. The magnitude of flux reactivation varied directly and monotonically with the ATP level. The data constitute the first unequivocal evidence for a reversible ATP dependence of thiol groups functionally involved in the thiol-dependent K+-Cl- transporter, suggesting that thiol-dependent and volume-sensitive K+-Cl- transport systems are operationally different.