Evidence for stimulation of the K-Cl cotransport system by phenazine methosulfate

The effects of phenazine methosulfate (PMS), a known generator of oxygen free radicals, on ion transport in human erythrocytes were studied. The treatment of the red blood cells with 0.1-0.8 mM PMS caused the concentration-dependent increase of K loss from the cells in K-free sodium chloride medium. The PMS-dependent K efflux from the cells in oxygen-free medium, being in equilibrium with argon, did not differ from the control. After substitution of Cl- ions in the medium by NO3-, PMS caused only a small activation of K loss. PMS at a concentration of 0.8 mM was found to increase passive K transport in erythrocytes (ouabain-furosemide-resistant 86Rb influx) and at the same time to decrease active transport of K (ouabain-sensitive influx of 86Rb). Furosemide-sensitive cotransport of K was not affected by 0.8 mM PMS. The influx of 22Na in the red blood cells was also independent of the presence of 0.2-1.0 mM PMS in the bath medium. The results obtained suggest that PMS stimulated the reversible K-Cl cotransport in human erythrocyte membranes. This effect of PMS resembles the action of the well-known SH-alkylating agent, N-ethylmaleimide.