Trace metals and hemoglobin metabolism.

Hemoglobin is composed of two pairs of globin chains to which are attached four iron-containing metalloporphyrins. Factors regulating hemoglobin synthesis include the availability of iron and the presence of heme. Heme production occurs by enzymatic synthesis and includes a step mediated by aminolevulinic acid dehydrase, which is zinc-dependent and, thus, susceptible to the toxic effects of other metals. The intake of iron, copper, zinc, cobalt, manganese, cadmium or lead may affect hemoglobin levels by an influence on availability of iron or heme.