RBC turnover in normal control mice and

p45nfe2^−/−mice.(A) RBCs were labeled by means of tail vein injection of biotin. At time zero, more than 95% of the cell population was biotinylated. The normalized number of biotinylated RBCs (± SD) as a function of time are shown for 4 control (circles) andp45nfe2^−/− (squares) mice. (B) RBCs were collected from control andp45nfe2^−/− mice, biotinylated, and reinjected into the tail vein of control mice. At time zero, 7% to 10% of the cell population was biotinylated. The normalized number of biotinylated RBCs (± SD) as a function of time are shown for control RBCs (circles) and p45nfe2^−/− RBCs (squares) injected into 4 different control mice. The data were fitted to the following equation: percentage of biotinylated cells = (100−(100/T)*t) exp(−kt), in which T equals the time at which the average RBC leaves the circulation (mean potential lifespan), t equals the sample time in days, and k equals the rate of random removal.