Research On The Internal Mechanism Of Zebrafish Biological Gradual Behavioral Response Based On The Analysis Of AChE Enzyme Activity And Receptor Activity In Vivo

With the economic development,heavy metals and pyrethroid drugs have caused great harm to water.Heavy metals can be taken into the body without consuming energy,heavy metals entering the body generally can not be excreted,showing the effect of accumulation of toxicity.Cadmium is a toxic heavy metal elements,with high toxicity,refractory,easy to residue and so on.Compared with organochlorine,organophosphate and carbamate pesticides,pyrethroid drugs are widely used in agricultural pests,pest control and food storage and so on because of their high efficiency,low toxicity,low residue and easy degradation.Deltamethrin is the most toxic one of pyrethroid insecticides.In the absence of pyrethroid pesticide hydrolase system,deltamethrin can not be hydrolyzed.Acetylcholinesterase is a key enzyme in the process of nerve conduction.The changes of AChE activity in aquatic organisms can be used as biomarkers of water pollution.Cholinergic receptors are differentially expressed throughout the central nervous system and play a central role in cell proliferation,survival,neuronal differentiation,gene expression regulation,synapse formation and maturation,prominent path-finding and neurotransmitter release.Aquatic organisms adapt to the external environment coercion has also changed in the external behavior,AChE and external behavior may exist some kind of response.In our research,the median lethal concentration of cadmium chloride and deltamethrin to zebra fish 48h was measured as one toxic unit?1.0 TU?to achieve the unification of different pollutants on zebra fish toxicity,then the effects of different concentrations of pollutants on AChE activity in zebra fish liver were determined by continuous exposure.The time difference of AChE inhibition in different tissues?gills,muscles,liver and brain?was analyzed in the experiment,meanwhile,the changes of the expression of muscarinic receptors?M3a receptors?under the stress of pollutants were studied,we are aimed to explain the internal mechanism of the external behavior of zebra fish.The results show that:?1?The 48 h median lethal concentrations(LC₅₀-48h)of cadmium chloride and deltamethrin in zebra fish were 42.60 mg/L and 5.20?g/L respectively,which indicates that deltamethrin is a hypertoxic compound to zebra fish,while cadmium chloride is a high toxic compound.The toxic effects of different pollutants on zebra fish are quite different,and the tolerance of zebra fish to both pollutants is also different,this may be due to the different mechanisms of toxicity of the two pollutants on zebra fish.?2?Deltamethrin and cadmium chloride 48 h showed a control>0.1 TU>1.0 TU>2.0TU change under the exposure of each concentration group,showing a good toxic dose effect relationship,The AChE activity of liver in the experimental group was significantly different from that in the control group.At 48 h exposure to DM,the AChE activity of 1.0 TU and 2.0 TU liver decreased rapidly at 0.5 h,indicating that deltamethrin had a toxic effect on zebra fish at the beginning of exposure.There were different changed after 1 h.The AChE of liver in 0.1 and 2.0TU group appeared extreme value after DM exposure for 4 h,and then decreased gradually.The extreme value of relative AChE activity in 1.0 TU concentration group appeared at 8 h after exposure.Under the continuous exposure of CdCl₂,48h,the AChE activities of liver in 0.1 TU,1.0 TU and 2.0TU decreased rapidly within 1 h,and there was a downward inflection point around 1 h,indicating that CdCl₂ had toxic effects on zebra fish at the early stage of exposure.After 1 h,there were different changes,0.1 TU rose to an extreme point when exposed to 8h,while 1.0 TU and 2.0 TU appeared at about 2 h,which may be the adaptation and adjustment of zebra fish to the external environment under external environmental stress.Under the exposure of the two drugs,the changes of AChE in the liver of zebra fish showed a general down-up-down,which coincided with the SBRM.?3?In DM exposure,the liver and muscle AChE were inhibited later.The time difference of the AChE inhibition in zebra fish was observed in different order according to tissues with time delay in sublethal treatments:the AChE was first inhibited in brain by chemicals followed by gill,muscle and liver?brain>gill>muscle>liver?in Cadmium and DM.At high concentration?1.0 TU,2.0 TU?,the order of inhibition of AChE activity in different tissues of zebra fish was almost synchronous,meanwhile,the higher environmental pressure caused the faster AChE activity to be inhibited.?4?At all time points,the relative expression level of M3a in brain tissue was the highest,and the relative expression level of M3a in gill tissue was the lowest.Under 0.1 TU,DM exposure,the relative expression of M3a at 5 time points was in sequence of brain>muscle>liver>gill,and the relative expression of muscle was higher than that of liver M3a.The relative expression of M3a at 11 time points is brain>liver>muscle>gill,and the relative expression of liver is higher than that of muscle M3a.Under the 10%surface water DM exposure,the relative expression levels of M3a in seven time points were in the order of brain>muscle>liver>gill,and the relative expression of muscle was higher than that of liver M3a.At 9 time points,the relative expression of M3a was in the order of brain>liver>muscle>gill.The relative expression level of liver in M3a was higher than that of muscle M3a.