Ion Movements in Red Cells Treated with Propranolol

Addition of propranolol to a suspension of human red cells was found to cause outflow of K+ ions and, to a lesser degree, inflow of Na+ ions, until a new stationary state was reached in which their cell/medium concentration ratios did not deviate much from unity. The cell volume decreased. Lactic acid production increased slightly. Against the outflow of bulk K+ ions, tracer K+ and Rb+ ions accumulated very rapidly in the cells and then began to flow out. The ratio of inward to outward rate constant of K+ tracer immediately decreased, while that of Na+ tracer increased, transiently exceeding the medium/cell concentration ratio of Br‐ tracer, in which no abrupt change occurred. In the propranolol‐induced stationary state the cationic tracer rate constants were higher than in the untreated cell, but not so high as just after addition of propranolol. Their order was K.+ > Rb+ > Cs+ > Li+ > Na+. It is suggested that an accelerated “carrier”‐mediated exchange diffusion of cations across the cell membrane, driven by the flow of bulk ions down their gradients, would explain the rapid tracer ion movements.