Carrier-mediated residual K+ and Na+ transport of human red blood cells.

Residual, i.e., (ouabain, bumetanide, and EGTA)-insensitive K+ and Na+ influxes as well as effluxes of human red blood cells are enhanced in isotonic solutions of low (NaCl + KCl) concentration using sucrose to maintain constant osmolarity. Various carrier models were tested to fit the experimental data of these fluxes simultaneously. The residual K+ and Na+ fluxes can be described on the basis of a carrier mechanism of competing substrates with modifier sites.