A reappraisal of the effects of iron and desferrioxamine on the growth of Plasmodium falciparum 'in vitro': the unimportance of serum iron.

It has been suggested that P. falciparum takes up iron from serum and that desferrioxamine, an iron chelating agent, inhibits parasite growth. We have now shown, however, that when all the iron is transferrin bound, P. falciparum, in culture, takes up less than 7 pmol Fe/10(9) parasites/24 h and that incorporation is increased only in the presence of a high molecular weight iron complex not naturally found in serum. Furthermore, removal of iron serum did not reduce parasite growth, and addition of excess iron was inhibitory. Desferrioxamine inhibited growth, but this inhibition was reduced under conditions in which the transfer of iron from transferrin to desferrioxamine was accelerated. We conclude that P. falciparum does not directly utilize serum iron and that desferrioxamine does not inhibit the parasite by interfering with the supply of iron from the incubation medium. The results are relevant to clinical data which suggest that added nutritional iron enhances the host susceptibility to malaria.