Effect of hypoxic exposure on iron absorption in heterozygous hypotransferrinaemic mice

Heterozygous hypotransferrinaemic mice show serum iron, haemoglobin and reticulocyte levels similar to those of normal (+/+) controls but the plasma apotransferrin level is significantly reduced. Male heterozygous hypotransferrinaemic Balb/cJ mice and control (+/+) littermates were exposed to 1-3 days' hypoxia at 0.5 atmospheres. Controls increased their haemoglobin and iron absorption significantly during the first day of exposure; serum transferrin levels were increased and iron absorption had returned to normal levels by the third day or serum transferrin above normal levels and the elevated iron absorption persisted for longer than in controls. Serum iron levels were lower following hypoxic exposure than in controls. Liver iron loading was significantly enhanced by hypoxia in heterozygotes, but not in controls. These observations demonstrate the importance of the reservoir of plasma apotransferrin in the initial phase of enhanced erythropoiesis, and that the ability to enhance plasma levels of iron-bound transferrin is required in order to increase haemoglobin levels under the hypoxic stress.