THE KINETICS OF IRON METABOLISM IN NORMAL GROWING SWINE

Plasma and red cell iron turnover rates were determined in 18 normal growing swine by the use of tracer doses of Fe(59). Body surface counting was performed on a representative group of animals following the injection of the isotope. The mean half-time of plasma iron disappearance was 1.19 ± 0.26 hours. Two exponential rates of disappearance of Fe(59) from the plasma were observed in 15 of the pigs and a single rate was observed in the other 3. The mean plasma iron turnover rate was 1.11 ± 0.34 mg./kg. day. The average maximum incorporation of Fe(59) into the erythrocytes was 92 ± 9 per cent. The mean red cell iron incorporation rate was 1.10 mg./kg. day, but an average of 0.42 mg./kg. day of this was calculated as being due to increasing red cell mass incidental to body growth, so that the true mean red cell iron turnover rate was 0.59 ± 0.19 mg./kg. day. The average "apparent" red cell life span was 63 ± 16 days. This is in agreement with the red cell life span of 62 days determined previously with glycine-2-C(14).