Effects Of Norfloxacin Lactate On The Immune System Of Takifugu Oblongus And Epinephelus Coioides

The abuse of antibiotics and the improper treatment of them contribute to their high residual quantity in the environment.The frequent use of antibiotics in aquaculture not only exacerbates the pollution of antibiotics,but also poses a threat to the health of fish and shellfish.Norfloxacin Lactate(NOR)is an antibiotic widely used in the aquaculture.In the present study,most studies focus on antibiotic drug toxicity and antibiotic resistance crisis.However,the effects of antibiotic especially the quinolones antibiotics on the fish immune system are rarely known.In this thesis,the consequences of NOR on the nonspecific immune responses'(red blood cells(RBCs)count,serum lysozyme(LZM)activity,interferon-y(IFN-y)levels)and specific immune responses(Immunoglobulin M(IgM)levels)of Takifugu oblongus(T.oblongus)were evaluated after 1,4,7 and 10 days of treatment.Three experimental groups(0.5,5 and 50 mg/L)and control group were established.For the second time,the consequences of NOR on the nonspecific immune responses(RBCs,LZM,IFN-y,Complement 3(C3)?Interleukin-8(IL-8)?specific immune responses(IgM)and immune-associated genes's(C3 and IgM)expression levels of Epinephelus coioides(E.coioides)were evaluated after 1,7,14,21 and 28 days of experiment.The first 21 days were set for exposure,and then the fish were moved into clean ocean for 7 days as a recovery experiment.Three experimental groups(0.05,0.5 and 5 mg/L)and control group were established.The results show:(1)Exposure of NOR could stimulate or inhibit the non-specific immune response of T.oblongus and E.coioides.The results reveal a significant decrease of RBCs in both T.oblongus and E.coioides,and the higher exposure concentration,the greater damage on RBCs.The serum LZM activity of the two species was stimulated in the first 10 days after exposure.The value of E.coioides was significantly decreased after 14 days' exposure.Higher concentration of NOR has more obvious effect on the LZM activity.The levels of the two species of fish's IFN-y,E.coioides'C3 and IL-8 were stimulated by 0.5 mg/L and 5 mg/L NOR.The stimulating effect of 0.05 mg/L group appeared in the early stage of the exposure,while the effect of 5 mg/L group appeared in the middle to late period of the exposure.No obvious dose-effect relationship showed between the groups.(2)Exposure of NOR could stimulated the specific immune response of T.oblongus and E.coioides.The level of total IgM in the head kidney from the two species of fish were higher than the control during the exposure.The stimulating effect of 0.5 mg/L group was observed in the first 4 days of exposure,while the effect of 5 mg/L group was showed after 7 days of exposure.No obvious dose-effect relationship showed between the groups.(3)NOR caused the significant variation in the expression of immune-associated genes(C3 and IgM)of E.coioides' head kidney.The value of the C3 gene expression of E.coioides were up-regulated during exposure.While the value of the IgM gene expression of E.coioides were inhibited first and then up-regulated repeatedly,indicating that NOR has greater toxicity on IgM than C3.(4)After 7 days' recovery after exposure,NOR showed a persistent immune toxicityon E.coioides.The inhibition of RBCs and serum LZM activity could not recover within 7 days.The levels of the non-specific immune parameters(IFN-?,C3,IL-8)and the specific immune parameter IgM were significantly decreased.The expression of C3 mRNA and IgM mRNA in the experimental groups were significantly inhibited after recovery.These indicated that although E.coioides was recoverd for 7 days after 21 days' exposure,the immune toxicity it suffered still existed.