Changes of the activities of superoxide dismutase after exposure to the fume of heavy metals and the significance of zinc in the tissue

Pathological changes induced by cadmium aerosol had features common to the changes evoked by oxidants. Female rats were exposed to fumes of lead, antimony, zinc and cadmium (15–100 nmoles/m³). One hour after termination of exposure, superoxide dismutase (SOD) activity in erythrocytes of the exposed rats lowered by 15–40%. SOD activity of lung lavage fluid also lowered by 20–35% at the 2nd day after the exposure. The inverse value of SOD activity (l/SOD) in erythrocytes and of lung lavage fluid were proportional to the molar exposure level adjusted by the particle size (Dixon plot), irrespective of the difference of the exposed substance. The ratio of dry weight to wet weight of the lung was 4.3–26% lower than the control value on the later period after the exposure. With the heavy metal exposure, the uptake of the exposed metal was found to be proportional to the endogenous zinc concentration, which was correlated well with the change of SOD in the lung and in erythrocytes. Cadmium decreased the zinc concentration after the exposure.