[Modulation of the expression of transferrin receptors by iron, hemin and protoporphyrin IX].

The expression of transferrin receptors in human leukemic cell lines was investigated. Our results have clearly shown that heme, iron and protoporphyrin-IX may modulate the expression of Trf receptors: iron and heme induce a decrease in the number of Trf receptors; in contrast protoporphyrin-IX elicited a significant increase in the number of Trf receptors. On the basis of these data we suggest that the intracellular concentration of iron, heme and protoporphyrin-IX may represent the main factor involved in the regulation of the expression of Trf receptors.