Changes in erythrocyte membrane Na –ATPase associated with cell maturation and ontogeny

Age-related changes in the transport ATPase system of mammalian erythrocyte membranes have been investigated. Two developmental processes were followed, maturation of reticulocytes in humans, rabbits and low-potassium sheep, and development of erythrocytes during ontogeny in LK lambs. Human and rabbit erythrocytes contain similar high potassium concentrations, though human membranes exhibit more alkali cation-dependent ATPase than rabbits. In both species, a decline in this activity is observed with cell maturation. LK sheep erythrocytes have low potassium content and little Na+-dependent ATPase. Reticulocytes possess elevated potassium levels and increased ATPase activity. Both parameters decrease during maturation, but the loss of ATPase activity is due mainly to a decrease in the Mg++-dependent component. LK lamb erythrocytes possess elevated potassium content and ATPase activity. Na+-ATPase resembles HK rather than LK erythrocytes, both in quantity and K+-response kinetics. Ontogeny is associated with changes in cell potassium levels and Na+-ATPase activity to mature LK characteristics