Iron chelation in thalassemia: mechanism of desferrioxamine action

The mechanism of iron chelation was studied in 16 patients with homozygous beta-thalassemia. Following the i.v. infusion of desferrioxamine, chelated iron accumulated in the plasma and its maximal level at 2 h was closely correlated with the 24-h excretion of iron in the urine. The high specific activity of chelated urinary iron indicated that the chelatable pool was much smaller than the total storage iron pool and was probably derived from nonviable red blood cells in the reticuloendothelial system. This postulate was confirmed by the direct measurement of specific activities in the spleen and liver, revealing identical values of chelated urinary iron and of iron in reticuloendothelial tissues. These findings support the concept of an easily chelatable iron pool that is derived from the catabolism of hemoglobin.