Enhancement of Oxygen Toxicity by the Herbicide Paraquat1–3

Despite the cyanosis seen in some patients intoxicated with the herbicide Paraquat, theoretic considerations suggest that inhalation of oxygen-enriched gas mixtures might be harmful to them. This clinical dilemma led to studies in rats and 3 additional mammalian species to confirm the expected harmful interaction. During previous experiments, 186 rats given a standard intravenous dose of 27 mg of Paraquat per kg of body weight survived 24 hours in air, and of 134 at risk for an additional 24 hours, 131 survived. In the studies now reported, 19 of 20 similarly treated rats died before 22 hours in an atmosphere of oxygen. Microsections of lungs from rats exposed to both Paraquat and oxygen-enriched gas showed extensive perivascular and alveolar edema, abnormalities known to occur in rats after longer exposure to oxygen alone at 1 atmosphere. These findings suggest that Paraquat injures the lung in rats by potentiating the toxic effects of oxygen. Because Paraquat might also intensify pulmonary oxygen toxici...