Changes in the erythrocyte sodium pump with age.

Various estimations of the erythrocyte sodium pump were determined in 18 female and 11 male adult subjects. In the female group, but not in the male group, the sodium concentration increased with age; the erythrocyte active transport decreased and passive transport increased with age and could account for the observed change in erythrocyte sodium concentration with age. The erythrocyte Na-K ATPase decreased with age in the females and this could account for the observed change in active transport.