Erythrocyte sodium, potassium and sodium fluxes with cell and subject ageing

In young subjects erythrocyte sodium was lower in females than in males. In males juvenile erythrocyte sodium decreased with subject age whereas in females aged erythrocyte sodium increased with subject age. Therefore, the difference in erythrocyte sodium between young male and female subjects was not observed in the elderly. These differences in erythrocyte sodium appeared to be mainly due to differences in the sodium pump rate constant. In juvenile cells from young subjects the sodium pump rate constant was related to the ouabain sensitive sodium flux rate, but not in elderly subjects, suggesting disturbed control of cell sodium in the latter group. Juvenile erythrocytes had a higher potassium content in elderly than young subjects but this was mainly in the 'frail' hospitalised elderly and it decreased more rapidly with cell ageing. This could indicate more active erythrocytes entering the blood in elderly subjects and then ageing more rapidly. Differences between young and elderly subjects in erythrocyte sodium, potassium and sodium pump rate constant were more marked in the 'frail' hospitalised elderly.