Synergic lung changes in rats receiving combined exposure to paraquat and ionizing radiation

Experiment was carried out on a total of 160 male Wistar rats. Paraquat was instilled per os intragastrically by a metal probe, in aqueous solution, at a daily dose of 0.46 mg/kg body wt given five times a week for 4 months. Directly upon termination of paraquat intake the animals received a single external whole-body exposure to 4 Gy of ionizing radiation. Changes in the parameters studied were recorded on Post-treatment Days 1, 5, 10, and 30. In bronchoalveolar lavage fluid (BALF), paraquat treatment alone was found to elevate lactate dehydrogenase (LDH) activity and content of thiobarbituric acid (TBA) reactants; lung homogenate from this treatment group showed diminution in superoxide dismutase (SOD) and catalase (CAT) activities and in content of nonprotein sulfhydryl groups (NPSH) on Days 1 and 5. Irradiation alone produced less substantial changes. With combined exposure to paraquat and radiation, there was more marked and more prolonged depression of the three parameters (SOD, CAT, and NPSH) of lung antioxidant defense and synergic increase in BALF content of TBA reactants and LDH activity.