Age-dependent loss of serum iron with concomitant elevated transferrin level in fsn mice. (A) Serum iron was measured in fsn and normal mice as they aged from 1-week-old pups to 5-week-old adults. Serum iron decreases as fsn mice age, whereas serum iron levels rise with age in normal mice. (B) Transferrin levels were assessed by electrophoresis of sera samples on cellulose acetate strips, and bands were visualized by staining with Ponceau S. Sera were collected from 1-week-old fsn and hea pups and adult fsn mice with age-matched normal littermate controls. The cellulose acetate strips were scanned and relative intensities noted for transferrin and albumin. Ratios of these 2 proteins were calculated and compared to normal. Transferrin is slightly elevated in hea pups (1.3 times more transferrin compared with normal littermates). Adult fsn mice were determined to have 2.8 times more transferrin than normal littermates (P < .001). Error bars indicate SEM.