Oxygen toxicity related to exposure to lead

We evaluated superoxide dismutase (EC 1.15.1.1) and glutathione peroxidase (EC 1.11.1.9) activities in the erythrocytes of lead-exposed and nonexposed workers from distinct industries localized in the State of São Paulo, Brazil. Concentrations of either lead or protoporphyrin IX, or both, in blood were used to indicate the extent of exposure. In all cases, values for superoxide dismutase were significantly higher in the exposed workers. The dose-response relationship between this enzyme and lead concentrations was roughly linear for the workers with greater than 40 micrograms of lead per 100 g of blood. Except for the sample from one of the industries, the corresponding glutathione peroxidase activities were also significantly higher in lead-exposed workers. These data, together with those previously found for patients with intermittent acute porphyria, suggest that in both groups the accumulation of heme precursors is connected to the exacerbated production of activated oxygen species.