Erythrocyte cation transport and age: effects of digoxin and furosemide

The uptake of rubidium 86 (86Rb) by human erythrocytes was measured at various ages. Effects of digoxin and furosemide on this process were examined and, in the case of digoxin, related to its numbers of specific cellular binding sites. There were no significant effects of age on absolute cellular Rb uptake, digoxin-sensitive Rb uptake, or numbers of cellular binding sites for digoxin, but the ability of digoxin to inhibit digoxin-sensitive 86Rb uptake increased with age. The ability of furosemide to inhibit digoxin-insensitive 86Rb uptake did not change with age. Results suggest a dynamic contribution to altered sensitivity to digoxin in elderly persons.