Reactive oxygen species involvement in ricin-induced thyroid toxicity in rat

1 Ricin is known to have diverse effects on the cells of different organs like liver, kidney, pancreas, intestines and parathyroid. 2 Acute decrease in serum thyroid hormone levels 24 h after ricin administration (1.5 μg/100 g) led us to suspect the toxic action of ricin on the thyroid. 3 We monitored the lipid peroxidation (LP) and anti oxidant status of the thyroid tissue to determine the role, if any, played by reactive oxygen species (ROS) in this pathology. 4 An increase of 39% in LP and 47% in superoxide dismutase, along with a 8.5% decrease in catalase points to the imbalance in the antioxidant defence involving hydrogen peroxide and its univalent reduc tion product, the hydroxyl radical. 5 Thyroid histopathology shows destruction of thyroid follicles and necrosis, which may be due to ROS and may partly explain the 50% reduction in circulating thyroid hormones seen after ricin administration.