Study On Effects Of Melamine On Enzymatic Activities Of Tilapia In Aquaculture Water

Melamine is widely used in industry, which can enter into water environments including aquaculture water through various routines. In addition, melamine has been deliberately added into fish feed to boost its apparent protein content. Therefore, it is necessary to investigate the effect of melamine in water and feed on fish health, and find out biomarkers for monitoring melamine pollution.The metabolic pathways of toxic and harmful substances in organisms involve detoxification pathways and REDOX cycle approaches, which are related to some important metabolic enzymes such as7-ethoxyresorufin-o-deethylase (EROD) and glutathione-s-transferase (GST), and antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT).Tilapia, one of the most important commercial fishes in China, was selected as the research object of this work. Using a simulated aquatic ecosystem, effects of melamine on the activities of above-mentioned enzymes in tilapia were examined.The main research contents and results are shown below.1. Effects of melamine on activities of EROD, GST, SOD and CAT in tilapia liver and kidney through waterborne exposure. Results show that compared with the control group, tilapia metabolic enzymes in the liver and kidney and the activity of antioxidant enzymes in Id were induced, and with longer duration of exposure all present certain change rules. Overall, tilapia EROD enzyme in the liver and kidney, GST enzyme, the activity of SOD and CAT in the liver appears induced-suppressed-induced trends. But as time extended, all of this is suppressed again; Tilapia CAT activity in the kidney appear induced-suppressed trends. To some extent the results also show that EROD enzyme, GST enzyme, CAT and SOD enzyme enzyme activity can be used as indicator of melamine contamination of aquaculture water in biological monitoring.2. Effects of melamine on activities of EROD, GST, SOD and CAT in tilapia liver and kidney through feeding exposure.Results show that in the10d of feed exposed, tilapia liver EROD, GST, CAT and SOD activity appeared induced-suppressed trends, in the last10d after feed exposed, four enzyme activity in the liver were eventually returned to the early levels of feed exposed, there was no significant difference with control group. EROD, GST and CAT in the kidney also present induced-suppressed trend, SOD activity continues to be suppressed, but after the feed exposed, activity has increased, though stop feed exposed10d (raised20d) its activity is still being suppressed, but there was no significant difference with control group. With the presence of melamine, the CAT in the tilapia liver and kidney, SOD, EROD and the significant variation in GST enzyme activity and enzyme activity of time-effect relationship, that melamine has disrupted the normal function of the liver and kidney enzymes, and when stopping in the feed exposed test, therer function are back to normal. To some extent, on the other hand, the CAT, SOD and EROD and GST enzyme activity changes can be used as indicator of melamine contamination in biological monitoring.3. The dose-effect relationships between melamine concentration and activity change of enzymes in tilapia liver and kidney under different waterborne exposure concentration. The results showed that early exposure to different concentrations of melamine in tilapia in the liver and kidney increased with the exposure time, the content of0.02g·L-1,0.05g·L-1and0.1g·L-1were maximum at the time of6d, and the liver in0.1g·L-1attain to the maximum amount of58.03mg·kg-1, kidney in0.05g·L-1attain to the maximum amount of41.74mg·kg-1. At the end of the exposure, the liver of the concentration of0.1g·L-1dropped to1.08mg·kg-1, back to the early exposure level. Through15d exposure with different concentration groups of melamine in tilapia liver and kidney, the result shows that with the increase of concentration of melamine, melamine content gathering in the liver and kidney is on the rise, and the amount of enrichment in the kidney is higher than the liver. In0.1g·L-1, melamine content in liver and kidney were12.47mg·kg-1and20.33mg·kg-1.This was the time to analyse the sample after15d, under (0.01～0.05g·L-1) concentration range, melamine present activity of tilapia liver entrainment, and entrainment enhanced with the increase of concentration of infected; The melamine concentration is0.1g·L-1, liver EROD activity phenomenon plummeted, compared with control group, significant difference (P<0.05). For kidney in (0.01～0.02g·L-1) within the scope of the melamine to kidney produce inhibition, and the inhibition enhanced with concentration; When the concentration of0.05g-L"1, melamine in tilapia kidney had an induction effect and induction effect enhance with the increase of concentration. Through the tilapia EROD activity of enzymes in the liver and kidney by regression analysis, in (0.02～0.1g·L-1) concentration range, the kidney in between EROD activity and concentration of melamine have significant dose-effect relationship.In (0.01～0.05g·L-1) concentration within the scope of the industrial chemical melamine to tilapia liver GST activity presents the entrainment, in0.05g-L"1induction rate is as high as59.31%, when compared with group difference was significant (P<0.01); In0.1g·L-1, hepatic GST activity phenomenon plummeted, compared with the control group, there was no significant difference. For kidney, melamine has inhibitory effect on the GST activity; Compared with control group,0.01、0.02、0.05g·L-1kidney GST activity concentration group were significant (P <0.05) and significantly (P<0.01). Through the tilapia GST enzyme activity in the liver and kidney regression analysis, in (0.01～0.05g·L-1) concentration range, the activity of GST and melamine in the kidney has a significant dose-effect relationship between concentration.In (0.01～0.1g·L-1) melamine concentration range of tilapia liver the activity of CAT had an adverse effect. Through the regression analysis was carried out on the tilapia liver enzyme activity of CAT, in (0.02～0.1g·L-1) concentration range, the activity of CAT in the liver and melamine concentration has a significant dose-effect relationship between. In (0.01～0.1g·L-1) within the concentration range of tilapia kidney is presented inhibiting-induced suppression-induced changes in the trend, compared with control group, the differences were significant (P<0.01).In the concentration range, tilapia liver SOD activity of inhibiting-induced suppression-induced trends, under the concentration of0.02g·L-1entrainment, strongest induction rate is as high as43.09%, compared with control group, the difference was significant (P<0.01). Within the scope of the concentration of melamine renal SOD activity of tilapia are produced entrainment, at0.1g·L-1entrainment, strongest induction rate was40.87%, compared with the control group, significant difference (P<0.05). Activity of SOD in liver and kidney of Tilapia and melamine concentrations had no significant dose-effect relationship.Under the stress of melamine contamination, tilapia CAT and SOD in the liver and kidney, EROD and GST activity produced great changes. The change of SOD activity in the liver and kidney, to some extent, shows the kidney ability of scavenging free radicals is higher than the liver. There is a significant dose-effect relationship between melamine concentration and activity changes of EROD, CAT and kidney GST in tilapia liver, suggesting that these three enzymes can be expected to become biomarkers which reflecte the degree of melamine contamination in water.