亚硝酸盐氮胁迫对罗非鱼（GIFTOreoohromisniloticus）血清非特异性免疫酶活性的影响

试验设置了不同浓度亚硝酸盐氮（空白对照、0．75mg·L-1、1．50mg-L-1、3．00mg·L-1和5．00mg·L-1），研究了亚硝酸盐氮胁迫对罗非鱼（GIFTOreochromisniloticus）血清非特异性免疫酶（溶菌酶、碱性磷酸酶、补体c3）活性的影响。结果表明：罗非鱼血清碱性磷酸酶、溶菌酶、补体C3活性均呈现出随亚硝酸盐氮浓度升高而降低的趋势，且当亚硝酸盐氮浓度小于1．50mg·L-1时，罗非鱼血清碱性磷酸酶、溶菌酶、补体C3活性与对照组相比差异不显著（P〉0．05），说明低于1．50mg·L-1的亚硝酸盐氮不会对罗非鱼机体免疫力产生显著影响；而高于3．00mg·L-1的亚硝酸盐氮胁迫能够显著（P〈O．05）降低罗非鱼血清碱性磷酸酶、溶菌酶、补体C3活性，最大下降率分别达到31．75％、27．40％、14．43％，从而显示出高浓度亚硝酸盐氮（〉3．00mg·L-1）能够对罗非鱼机体产生强烈的氧化胁迫和免疫损伤，导致机体免疫力下降，增加罗非鱼对致病菌的易感性。本研究认为，3．00mg·L-1可能是亚硝酸盐氮胁迫引起罗非鱼机体免疫力显著降低的阈值。

Effect of nitrite nitrogen stress on the activities of nonspecific immune enzymes in serum of tilapia （GIFT Oreochromis niloticus）

In order to know the effect of nitrite nitrogen stress on the immunity of tilapia （GIFT Oreochromis niloticus）, the research on the response of lysozyme, alkaline phosphates and supplement C3 in tilapia serum under the stress of different concentrations of nitrite nitrogen （control, 0.75 mg.L-1, 1.50 mg.L-1, 3.00 mg.L-1 and 5.00 mg.L-1） were carried out indoor, The results showed that nonspecific immune enzyme activities in tilapia serum decreased with the increasing of the concentrations of nitrite nitrogen. The activities of lysozyme, alkaline phosphates and supplement C3 in tilapia serum didn＇t changed significantly （P〉0.05） when the concentrations of nitrite nitrogen were lower than 1.50 mg.L1, which meant that the low concentrations of nitrite nitrogen wouldn＇t have significant oxidative stress and immune injury on tilapia, and therefore the nitrite nitrogen wouldn＇t decrease the immunity of tilapia when it was lower than 1.50 mg.L1. However, the activities of lysozyme, alkaline phosphates and supplement C3 in tilapia serum decreased significantly （P〈0.05） when the concentrations of nitrite nitrogen were higher than 3.00 mg.L-1, which meant that high concentrations of nitrite nitrogen had strong oxidative stress and immune injury on tilapia and would decrease its immunity. It could be concluded from the research that 3.00 mg.L-1 might be the threshold value of nitrite nitrogen stress on tilapia＇s immunity.