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TISSUE DISTRIBUTION AND TOXICITY OF LEAD FOLLOWING IRON SUPPLEMENTATION

It has been postulated that iron(Fe) deficiency enhances the toxic effects of lead(Pb) in younger children. The present study shows that Fe supplementation has pronounced effects on the distribution and toxicity of Pb. The addition of FeCl3 (30μg Fe per 100ml plasma)to human blood resulted in a marked decrease in the uptake of added Pb210 by red blood cells. At equilibrium, 86.5±6.1%[14] of the added Pb remained in the plasma as compared to 15.6±4.0%[18] in the absence of additional Fe. The retained plasma Pb in the presence of added Fe is in the form of a stable macromolecular Pb complex. In the rat, intravenous administration of Fe followed by Pb, resulted in a similar failure of red cell Pb uptake. This was accompanied by an 80.3±38.6%[11] increase in Pb uptake by the liver and a 38.4±10.0%[11] decreased Pb uptake by the kidneys. Toxicity studies performed by injecting human plasma containing 55μgPb into the yolk sacs of 5 day chick embryos resulted in 88% mortality by day 12. Among these embryos, 94% showed gross brain hemorrhage and hydrocephalus. Similar embryos injected with Pb in plasma pretreated with Fe, showed a decrease in mortality(41%) and a markedly reduced incidence of gross brain damage(26%). These findings demonstrate an interaction between plasma constituents and Pb, which under conditions of Fe excess changes the tissue distribution of Pb and protects against its neurotoxic effects.