CONTEXT: Paraquat (PQ) causes lethal intoxication by inducing oxidant injury to the lung. Selenium is a cofactor for glutathione peroxidase (GPx), which is one of the major endogenous antioxidant enzymes.

OBJECTIVE: To determine whether selenium post-treatment activates GPx, decreases lung injury, and improves survival in PQ intoxicated rats.

MATERIALS AND METHODS: Male Spraque-Dawley rats were categorized into three groups: sham (n = 6), PQ (n = 12), and PQ + Se (n = 12). In the PQ and PQ + Se groups, 50 mg/kg of PQ was administered intraperitoneally. After 10 minutes, 60 μg/kg of Se (PQ + Se) or saline (PQ) was administered via the tail vein. Six rats per group were euthanized 6 hours or 24 hours later. Lung tissues were harvested for the measurement of GPx activity, reduced glutathione (GSH), glutathione disulfide (GSSG) and malondialdehyde (MDA) and for histological analysis. Using separated set of rats, survival of PQ (n = 10) and PQ + Se (n = 10) were observed for 72 hours.

RESULTS: GPx activity in the PQ group at the 6-hour and 24-hour time points was lower than in the sham group (p < 0.006). GPx activity in the PQ + Se group at the 6-hour and 24-hour time points was higher than in the PQ group at the same time (p < 0.006). GPx activity in the PQ + Se group at 24 hours was higher than at 6-hour time point and also higher than in the sham group (p < 0.006). The GSH/GSSG ratio in the PQ + Se group at 24 hours was lower than that in the sham group (p < 0.006). MDA levels in the PQ group at 6 hours and 24 hours were higher than in the sham group (p < 0.006). MDA levels at 24 hours in the PQ + Se group was lower than in the PQ group (p < 0.006). Acute lung injury (ALI) scores in the PQ group at 6 hours and 24 hours were higher than in the sham group (p < 0.006). ALI scores at 24 hours in the PQ + Se group were lower than in the PQ group. Survival rates did not differ between PQ and PQ + Se (p = 0.869).

CONCLUSION: Single dose of selenium post-treatment activates GPx and attenuates lipid peroxidation and lung injury early after paraquat intoxication, but does not improve 72 hours of survival.