| Metalaxyl is an amide-type broad-spectrum antibacterial agent,which has a good control effect on Saprolegniasis.With the ban of malachite green,metalaxyl as an alternative new drug is used in aquaculture increasingly.Metalaxyl residues in plants,the environment,and mammals have been explored,and metabolic studies and safety assessment studies have been explored,However there are few related research in aquatic products.In this paper,Carassius auratus gibelio is used as an experimental object to establish a method for detecting metalaxyl residues,to explore the accumulation of metalaxyl,and to explore the pharmacokinetic characteristics of metalaxyl in aquatic animals.Providing a scientific theoretical reference for the reasonable use of metalaxyl in aquaculture,and also providing efficient technical support for metalaxyl residue monitoring in aquatic products.The main research contents are as follows:1.Established a metalaxyl residue detection technology system in edible aquatic products including immunologically based colloidal gold enhanced immunochromatog raphy assay(GICA)on-site rapid detection method and application Laboratory retest method for high performance liquid chromatography(HPLC).Taking advantage of the high affinity and specificity of the metalaxyl monoclonal antibody,a colloidal gold test strip was assembled.After testing,the minimum detection limit of colloidal gold immunochromatographic test strips for detecting metalaxyl standard solution was 5 mg / m L,and there was no cross-reaction with many drugs such as enrofloxacin and sulfamethoxazole.The detection limit of Carassius auratus gibelio,Penaeus vannamei,Ruditapes philippinarum were 2mg /kg,2mg / kg,and 1mg / kg respectively.The method is simple to operate,does not need to rely on expensive instruments and professional operators,and shortens the detection time.It is suitable for rapid screening of metalaxyl residues in on-siteaquatic product samples.The high-performance liquid chromatography re-examination method showed a good linear relationship in the range of 0.05 ?g /m L-5.0 ?g / m L.The regression equation was y = 35.302 x + 0.311236,the correlation coefficient was 0.99,the limit of detection was 20 ?g / kg and the limit of quantitation was 30 ?g / kg.This method is automated,precise and sensitive.Combining the initial with retest method will improve the efficiency and accuracy of residual detection.2.Determined the concentration of metalaxyl in blood,muscle,liver and kidney by HPLC.The metabolic process and metabolism of metalaxyl in the Carassius auratus gibelio after immersion treatment at 0 mg / L,9 mg / L and 36 mg / L at room temperature(15 ?)were investigated.The results showed that: in the two metalaxyl concentration treatment groups,the concentrations of the compounds in Carassius auratus gibelio showed a consistent trend with time.After the drug treatment reached the peak for the first time at 8h,2h,8h,and 8h.Peak concentrations in the low-concentration group were 9.47 mg / L,117.53 mg / kg,56.94 mg / kg,64.19 mg / kg;high-concentration groups were 39.24 mg / L,317.59 mg / kg,278.22 mg / kg,and 281.1 mg / kg.The second peak appeared at 128 h,showing a "double-peak phenomenon",the drug concentration at the second peak is lower than the first peak.According to the peak time and drug action,the recommended duration of metalaxyl medicated bath is 2 hours.Metalaxyl is significantly enriched in the blood,liver,kidney,and muscle tissues of Carassius auratus gibelio.The accumulation amount is liver> kidney> muscle> blood,liver reaches the peak at the earliest and highest concentration.It is considered that liver is the Metalaxyl most important target organ for accumulation in Carassius auratus gibelio.It is believed that the liver-gut absorption or the first pass effect is the main reason that may cause reabsorption.3.Carried out a pharmacological study on the safety of metalaxyl in Carassius auratus gibelio.After 2 hours of metalaxyl medicinal baths at 0 mg / L,9 mg / L,and36 mg / L,To explore the safety of low-and high-concentration metalaxyl to Carassius auratus gibelio by observation of tissue sections,determination of antioxidant enzyme activity and gene expression levels of antioxidant enzymes and Pharmacoenzyme.After 2 hours of metalaxyl medicinal bath,the liver,intestine,kidney and muscle tissues of Carassius auratus gibelio were taken for fixation,andsections were made and stained to observe the damage of each tissue of Carassius auratus gibelio.Determination the activity of antioxidants such as SOD and GPX,and biological indicators such as ALT liver damage.QPCR was also used to determine the gene expression levels of SOD and GPX antioxidant enzymes and P450 1A and GABA A two drug metabolism-related enzymes.Studies have shown that both low concentration(9 mg / L)and high concentration(36 mg / L)metalaxyl do not cause significant tissue damage to the muscle and kidney tissues of allogynogenetic crucian carp;they cause damage to the intestinal tract and liver tissue and appear Intestinal villus rupture,hepatocyte vacuolation.Compared with the control group,the high-concentration treatment group can significantly increase the antioxidant capacity of the Carassius auratus gibelio(p <0.05),and the expression of MDA shows that the lipid oxidation level in the liver increases significantly at low concentrations.(P<0.05),but the expression of ALT showed that metalaxyl had no significant effect on the normal function of the liver(p> 0.05).The expression of antioxidant enzymes and related genes showed that high concentrations of metalaxyl increased the expression of SOD,GPx,and GABA A in the liver of Carassius auratus gibelio(p <0.05).It means in this condition metalaxyl can protect the Carassius auratus gibelio effective,maybe through the GABA A to increase the antioxidant capacity of Carassius auratus gibelio and inhibit oxidative stress. |
PDF Full Text Request