| In order to investigate the acute toxic effect of nitrite on grass carp (Ctenopharyngodon idellus), this dissertation studied the morphological and functional alterations of red blood cells (RBC), nonspecific immnunity, and antioxidative function of grass carp exposued to nitrite sodium. The morphology and function of RBC, the parameters for nonspecific immunity, and blood physiology and biochemistry were assasyed at0h,12h,24h,48h, and96h after nitrite exposure, respectively.1The acute effect of nitrite on the morphology and function of erythrocyte in grass carpThe erythrocytes appeared shrinkage and deformation in grass carp stocked in1.0mg/L and4.0mg/L groups. The morphology changed from normal oval to rounded, and majority of erythrocytes swelled and collapsed in16.0mg/L group. The morphology of erythrocytes changed unsignificant in0.5mg/L group. The RBC counts and hematocrit (HCT) were significantly lower than those of the control group after96h exposure. The concentration of hemoglobin (HB) decreased significantly whereas the content of methemoglobin (MET) increased significantly over the exposure time. A significant decline in the content of HB occurred in4.0mg/L and16.0mg/L group, while the content of MET significantly increased in1.0mg/L,4.0mg/L, and16.0mg/L group at96h.The results imply that acute nitrite exposure exerted significant impact on the morphology and function of erythrocyte in grass carp. Nitrite exposure could change the morphology of erythrocyte, and lead the reduction of RBC counts and HCT. A large number of HB was oxidized to MET, which result in the impairment of respiratory function of grass carp.2The acute effect of nitrite on the blood biochemical parameters of grass carpThe content of blood glucose (GLU) increased with the increase of nitrite concentration as well as exposure time. The GLU level of each treatment group was significantly higher than that of the control group as of48h exposure. Serum contents of total cholesterol (CHOL), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) showed downward trend after the elevation at12h. With the increase of nitrite concentration and exposure time, the serum concentration of CHOL, TG, HDL-C, and LDL-C decreased significantly at96h. Serum contents of both total protein (TP) and albumin (ALB) were significantly lower than those of control group at96h. The ration of albumin and globin (A/G) decreased significantly with the increase of exposure time as well as the nitrite concentration. The activity of lactate dehydrogenase (LDH) and glutamic-pyruvic transaminase (GPT) elevated significantly with the increase of nitrite concentration and exposure time.The results showed that nitrite exposure resulted in significant changes in GLU levels, protein metabolism, lipid metabolism, and metabolic enzymes activity in grass carp. The elevated GLU level indicates that fish in experimental groups suffer from stress caused by nitrite, and accommodate the metabolism of protein and lipids to the energy supplies for reestablishing homeostasis. Activities of GPT and LDH, as well as the metabolic inbitation of protein and lipid, may be implicated in the tissue damage.3The acute effect of nitrite on the nonspecific immunity and antioxidant properties in C.idellusThe counts of white blood cells (WBC) showed upward tendency with the increase of nitrite concentration and exposure time. Except for0.5mg/L group, the WBC counts of the treatment groups were significantly higher than that of control group. The serum content of component C3and C4declined after a temporary rise at the intial stage. Compared to the control group, the levels of C3and C4in the treatments significantly declined. The serum activities of acid phosphatase (ACP) and alkaline phosphatase (AKP) were significantly lower than those of control group at96h. The serum activity of superoxide dismutase (SOD) reduced significantlyas of24h. The SOD activitysignificantly declined in either4.0mg/L or16.0mg/L group at96h. Throughout the96h exposure, either the content of glutathione (GSH) or the serum activity of γ-glutamine cysteine synthetase (y-GCS) elevated initially and then reduced in all experimental groups. GSH content and y-GCS activity were significantly lower than those of control group at96h. The total antioxidant capacity (T-AOC) decreased with the increase of nitrite concentration as well as the exposure time. The T-AOC of all experimental group were significantly lower than that of the control group at96h.Given the reduction of serum complement C3and C4content as well as the weakened activities of ACP and AKP, it can be inferred that that acute nitrite exposure exerts deleterious effect on the non-specific immune function of grass carp. The reductions of both SOD activity and GSH content contribute to the decreased T-AOC, implying that the antioxidant performance in grass carp is impaired by nitrite. |
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