Effect of mouse transferrin injections on circulating levels, hemoglobin (A) and liver/erythrocyte uptake of the absorbed radioiron (B). The transferrin (Tf ) dose and sampling time (after last injection if more than one) are as indicated. Data: mean ± SD for 4 to 6 animals in each group except for the one studied 3 days post 2.2 mg dose, where n = 3. Detection limit for serum transferrin was 0.05 mg/mL. Any values below this level are therefore not indicated on the figure. *P < .05; **P < .02; ***P < .004 as compared with untreated homozygous mice.