Erythrocyte metabolism; the metabolic behavior of the cholesterol of human erythrocytes.

In the course of studies on the ageing process in the human erythrocyte, we have investigated the metabolic behavior of the cholesterol of the erythrocyte. This study was designed to determine whether the cholesterol of the human erythrocyte is in the dynamic state (2), or whether the cholesterol is incorporated into the newly formed erythrocyte and remains with the cell throughout the cell's life span, as does hemoglobin (3-6). A previous study (7) has shown that the cholesterol of the plasma is in the dynamic state. The rate of entry of cholesterol into the plasma of the circulating blood was measured by determining the rate at which deuterium is incorporated into the cholesterol of the plasma when an elevated concentration of deuterium in the body water is maintained at a steady level by repeated administration of deuterium oxide. In the studies described in this report, the same technique has been employed and the concentrations of deuterium in the cholesterol of the erythrocytes and of the plasma have been compared. Since the cholesterol of the plasma is in the dynamic state, the finding of a similar rate of turnover and a similar pattern of concentrations of deuterium in the cholesterol of the erythrocytes would favor the conclusion that the cholesterol of the erythrocytes is also in the dynamic state. The subjects of this study were a patient with the nephrotic syndrome and a patient with xanthomatosis tuberosum multiplex. A discussion of the mechanisms involved in the maintenance of hypercholesterolemia in these conditions is beyond