Experimental examination of the hypothesis of coupling between the sodium and potassium pump in erythrocytes

Abstract

The effect of iodoacetate and arsenate upon movement of sodium and potassium in rabbit blood has been investigated. The experiments of Scott & Hayward in Ulva lactuca were repeated in erythrocytes: arsenate prevents the K loss from red cells induced by iodoacetate without an effect upon Na increase in the cells (as measured by flame-photometer). However, separate analysis of influx and efflux by radioisotopes provides no evidence that arsenate activates K influx, when reduced by iodoacetate. Arsenate inhibits the K loss under iodoacetate by decreasing the K efflux. Influx of sodium is also inhibited by arsenate, but not as strongly. Thus the movement of both ions in the direction of decreasing electrochemical potential gradient is inhibited by arsenate. The greater action on K movement is compatible with the assumption that the passive movement of ions depends upon the radius of the non-hydrated ions not of the hydrated ions. It cannot be concluded from the experiments presented that the transport mechanisms for Na and K are independent of one another.