Sodium and calcium transport in cat red cells.

The transport of radioactive sodium and calcium in high sodium low potassium cat red blood cells has been studied under various experimental conditions. In these cells, calcium uptake was found to increase by 25-fold when cell volume was decreased from 1.0 normal to 0.55. Increasing cell volume from 1.0 to 1.1 normal was found to decrease calcium-uptake by 30%. N-ethylmaleimide, NEM, phloretin, colchicine, and vinblastine were found to inhibit Na-uptake by these cells. Among these four agents, phloretin was the most potent inhibitor of Na-influx. It appears that phloretin produces its effect through its interaction with the cell membrane and not with cell interior.