Lead potentiates iron-induced formation of reactive oxygen species

There are reports that lead may promote free-radical initiated events in biological tissue. However,there are also reports on the inability of lead salts to stimulate the production of reactive oxygen species in isolated systems. Furthermore, there is no well understood rationale as to why lead should exhibit pronounced pro-oxidant properties. We are reporting that while lead acetate does not initiate any excess generation of reactive oxygen species in a cerebral synaptosomal suspension, it has a marked ability to enhance the pro-oxidant properties of ferrous iron in the same system. This property was maximal at a lead concentration of 0.5 mM when major precipitation of lead salts occurred. Therefore, it may reside in the ability of iron to form an active chelate on the surface of insoluble lead salts. Such an interaction may account for the discrepancies in the literature concerning the relation between lead toxicity and oxidative stress.