Measurement of red cell lifespan by application of the occupancy principle

A new method of measuring red cell lifespan in vivo using radioiron is described. Plasma iron clearance and red cell utilization curves are followed after the intravenous injection of 59Fe as for routine ferrokinetic measurements; determination of stable iron in plasma and red cells are also made. Mean red cell lifespan and the flow rate of iron into erythropoiesis are determined from these data by applying the occupancy principle. With this method, the mean red cell lifespan in eight normal subjects was found to be 115 days with a range 103-124 days. Fifteen patients with haemolytic anaemias of differing severity were found to have shortened lifespans in the range 10-63 days. In 29 cases, 51Cr red cell survival studies were carried out in addition to the present technique. A good correlation was obtained between red cell lifespan using the present method and 51Cr red cell half disappearance time (P<0.001). The total iron flow through the plasma derived by the occupancy principle is less than the conventional plasma iron transport rate. (author)