Studies of in vivo iron mobilization by chelators in the ferrocene-loaded rat

The oral efficacy of the oral iron chelators 1,2-dimethyl-3-hydroxypyrid-4-one (CP20), 1,2-diethyl-3-hydroxypyrid-4-one (CP94) and desferrioxamine B (DFO) has been compared with intraperitoneal DFO in an experimental model of iron overload with similar biochemical and biophysical characteristics to those observed for human genetic haemochromatosis. The hepatic iron stores in the ferrocene-loaded rat were relatively stable and did not decrease at the end of the loading period. In contrast, the iron dextran rat model showed a rapid depletion of its iron stores 2 weeks after cessation of intraperitoneal injection. When CP20 and CP94 were administered to the ferrocene-loaded rat model in combination with an iron-free diet there were significant decreases in (i) total homogenate iron and (ii) hepatic ferritin iron when compared to the iron-loaded rat receiving the iron-free diet alone. Desferrioxamine, when administered by gavage, only showed chelation of ferritin iron, while intraperitoneal injection of desferrioxamine showed significant depletion of iron both in the total homogenate and ferritin. Subcellular fractionation of the hepatic organelle clearly showed that where there was depletion of homogenate iron there was a net decrease in the lysosomal fraction, while changes in ferritin iron were reflected by decreases in the cytosolic iron content. Although no assessment of net iron excretion was made, we suggest that the use of this animal model should ascertain the site of chelation by iron chelators.