Crhonic administration of paraquat produces immunosuppression of T lymphocytes and astrocytosis in rats

In this study, the impact of paraquat (1, 1-dimethyl 4, 4-bipyridiniumdicholoride) on rain-bow trout immune system and growth parameters was evaluated. In acute exposure, fish were dis-tributed into four groups and exposed to 0, 54, 90 and 150 mg L À1 of paraquat for 96 h. In chronic trial, fish were allocated into six groups and exposed to 0, 1.25, 2.5, 5, 10 and 20 mg L À1 of paraquat for 30 days. Growth performance (per-centage weight gain, condition factor and specific growth rate) and innate immune parameters (lyso-zyme, haemolytic complement activity and total immunoglobulin) were evaluated. Experimental data showed a LD 50 about 48.2 mg of paraquat per litre. Immunotoxic proprieties of paraquat especially in higher doses were shown in both tri-als. Total weight was also significantly decreased in chronic exposure when fish was subjected to 10 and 20 mg L À1 paraquat whereas other growth parameters were not affected in this experiment. In general, these results suggest that paraquat exposure in rainbow trout could suppress the immunological and growth parameters.