Study On Toxicity And Tissue Elimination Of Oxytetracycline In Allogynogenetic Crucian

Effects of oxytetracycline on physiological and toxicology of allogynogenetic crucian were analysized by determining the index of growth , physiology and biochemistry after the different dosage (0,100,250,625,1563,3907 mg/kg) were fed to allogynogenetic crucian in order to investigate an acute toxin test of oxytetracycline to allogynogenetic crucian carp. The tissue elimination of oxytetracycline in allogynogenetic crucian was also studied. The results are as follows:1. The allogynogenetic crucian carps, body weight: 45.7±5g, were injected with oxytetracycline from peritoneum when the water temperature was kept at 26℃, the mortality was noted at 24h,48h and 96h. The results showed that LD50 of the 24h, 48h and 96h were 1.90 g/kg,1.30 g/kg and 1.20 g/kg, separately. This indicated that oxytetracycline was hypotoxicity to allogynogenetic crucian carp.2. A feeding trial with allogynogenetic silver crucian carp was conducted to study the influence of dietary oxytetracycline (0,100,250,625,1563,3907 mg/kg) on growth ratio, nutriant composition and the activities of protease, amylase and lipase in hepatopancreas and intestinal tract. The results showed that the crude protein content of treatment group had a significant difference from the control group. The crude lipid content significantly increased in the 250 mg/kg group and the fish weight decreased while the dosage of oxytetracycline was over 625 mg/kg.The digestive enzyme activities were induced in the early period of the experiment. In the later period of experiment, the activities of protease in intestinal tract decreased while the dosage of oxytetracycline was above 250 mg/kg , the lipase activities and amylase activities in hepatopancreas also decreased with the dosage increasing while the dosage of oxytetracycline was above 250 mg/kg. The change of lipase activities and amylase activities in intestinal tract were not significant comparing with control group while the dosage was above 250 mg/kg.3. Crucian carp was fed diets containing 0 (control), 100, 250, 625 ,1563 and 3907 mg/kg of oxytetracycline for 2 months respectively, the activities of three antioxidant enzymes, such as Superoxide Dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and malonaldehyd ( MDA) as products of lipid peroxidant were determined at an interval of two weeks after the first feeding . The results showed that SOD activities ,CAT activities and GSH-Px activities of treatment group was induced in the early period of the experiment . In the later period of experiment , SOD activities gradually decreased with the increase of oxytetracycline dosage while the dosages above 250 mg/kg; CAT activities almost increased gradually with the increase of dosage of oxytetracycline, but a gradually decreasing tendency of CAT activities with the increase of dosage of oxytetracycline was observed while the dosages were bigger than 250 mg/kg; Activities of GSH-Px showed a rise trend. MDA contents had a obvious increase (P<0.05). Activity of Na⁺ /K⁺-ATP enzyme was gradually decreasing with the dosage gradually increasing. It can be concluded that antioxidant system of crucian carp may induce an increase of activity of antioxidase and clear up oxyradical when the dosages were less than 250 mg/kg, and a higher dosage which was more than 250 mg/kg may lead to disbalance of antioxidant system,lead to damage of tissue .4. The Esterase (EST) isozymes and SOD isozymes in liver and kidney of allogynogenetic crucian carp were analysized by polyacylamide electrophoresis (PAGE) and some serum biochemical parameters of allogynogenetic crucian carp were determined to get the toxic effect of oxytetracycline for allogynogenetic crucian carp after the six groups of fishes were fed for two months with different dosages of oxytetracycline (0,100,250,625,1563,3907 mg/kg) . The results showed that the crucian carp had a significant decrease in serum total protein (TP), albumin(ALB) and glutamic oxalacetic transaminase (AST), and a significant increase in triglyeride (TG) , glucose (GLU) , total cholesterol (TC), urea nitrogen (BUN), creatinine (CREA) and serum potassium ion in serum when the dosages of oxytetracycline in the diets were beyond 250mg/kg. On the contrary, there was no significant change below 250 mg/kg . These indicated that the liver and kindey function was disturbed by the oxytetracycline over 250 mg/kg. Activities of Esterase (EST) isozymes and SOD isozymes in liver and kindey also decreased significantly by electropherogram when the dosages were over 250 mg/kg. 5. After six groups fishes were fed for two months with different dosages of oxytetracycline (0,100,250,625,1563,3907 mg/kg), the spleen index ,head kindey index , antibacterial activities and lysozyme activities were determined to investigate the effect of oxytetracycline on non-specific immunity function in allogynogenetic crucian carp. The result showed that the antibacterial activities decreased significantly for 625 mg/kg dosage group. There was no significant difference between control group and treatment group in spleen index, head kindey index and lysozyme activities, which indicated that oxytetracycline did not influence the development of immune organ and only affect slightly non-specific immunity function of allogynogenetic crucian carp.6. The residues and elimination of oxytetracycline (OTC) in muscles and hepatopancreas of allogynogenetic crucian carp at water temperture 24-26℃were determined by high performance liquid chromatography. The suitably chromatographic condition were obtained. The mobile phase was a mixture of 0.01mol/L NaH₂PO₄ aqueous solution and acetonitrile (77:23v/v) at pH 2.5, the detecting wavelength was 355nm, the linear range of OTC was from 0.1μg/mL to 15μg/mL.The recoveries of OTC in muscles and hepatopancreas were 80.54% to 92.94%. The results demonstrate that the elimination rate of OTC in muscle is slower than that in hepatopancreas after the fishes were orally administrated at a dose of 75mg/kg body weight. The concentrations of OTC in hepatopancreas reached the maximum: 6.24μg/mL after the fish were orally administrated with OTC for twelve hours, and decreased to 0.07μg/mL after 72h. The concentrations of OTC in mucles is close to 0.1μg/mL after the fish were orally administrated with OTC for 96h.