Effect of nitrite on the non-specific immune responses of Ctenopharyngodon idellus

In order to evaluate the effects of nitrite on non-specific immune responses in Ctenopharyngodon idellus,C.idellus(0.15±0.05 g) were exposed to eight experimental groups(0,0.2,0.4,0.8,1.0,2.0,4.0,and 8.0 mg nitrite per liter).The concentrations of complement C3 and C4,glutathione(GSH) content,and the activity of superoxide dismutase(SOD) as well as γ-gutamylcysteine synthetase(γ-GCS) were assayed at 0 d,1 d,4 d and 7 d respectively after exposure.The results showed that acute nitrite exposure exerted deleterious effect on the non-specific immune function of grass carp.The concentrations of complement C3 and C4 were at the normal level or a significantly higher level when the nitrite concentration was below 1.0 mg/L.However,the concents of complements decreased significantly as the nitrite concentration above 0.1 mg/L.The activity of SOD increased significantly over the exposure time,while dropped significantly at 7 d after exposure in higher dose groups.The activity of γ-GCS generally increased significantly with exposure time,though it decreased at the late of exposure the teratments.The concentration of GSH in fish exposed to nitrite was significantly higher than that in control group at 4 d,but returned to control level at 7 d after exposure when the nitrite concentration was below 1.0 mg/L.