| In the present study, the effects of acute and chronic nitrous nitrogen exposure onthe growth, metabolism, metabolic enzymes, immune response, heat shock protein70(HSP70) expression and isozyme of sea cucumber, Apostichopus japonicus Selenkawere studied. Subsequently, the detoxification mechanism of A. japonicus against thenitrous nitrogen exposure was preliminarily disscussed. The main results are listed asfollows:1. Effect of chronic nitrous nitrogen exposure on the growth, respiration andmetabolic enzymes in sea cucumber, A. japonicus: The effect of chronic nitrousnitrogen exposure in different concentrations (1.95,3.52,6.25,10.94and19.54mg/L)on the growth, respiration and metabolic enzymes of the body wall, muscle, coelomicfluid in A. japonicus (wet weight (50.63±0.72) g) was studied by experimentalecology method. The results showed that the hexokinase (HK), pyruvate (PK), lactatedehydrogenase (LDH), succinate dehydrogenase (SDH) and malate dehydrogenase(MDH) acitivity as well as lacic acid (LD), glucose (GLU) and glycogen content wassignificantly influenced by chronic ambient nitrous nitrogen exposure. The specificgrowth rate (SGR) of the sea cucumber decreased significantly with increased nitrousnitrogen. The oxygen consumption rate (OCR) of the sea cucumber in each nitrousnitrogen concentration treatment firstly increased, and then decreased during theexperiment。The OCR peaked when the sea cucumber was exposed in the differentconcentrations of nitrous nitrogen. The HK, PK, LDH, SDH and MDH activiy as wellas GLU content of the body wall, muscle, coelomic fluid in the sea cucumber increased firstly, and then decreased gradually in the experiment duration, while theLD and glycogen content showed an opposite trend. In general, the response of themetabolic system in the sea cucumber was more sensitively in high than low ambientnitous nitrogen exposure,2. Effect of chronic nitrous nitrogen exposure on immune responses andheat shock protein70expression in A. japonicus: The effect of different ambientnitrous nitrogen concentrations (0.12,2.30,11.50and57.50mg/L) exposure onnon-specific immune response and heat shock protein70(HSP70) expression of thebody wall in A. japonicus (wet weight (48.96±0.88) g) was studied by experimentalecology method. The results showed that the acid phosphatase (ACP) activity, alkalinephosphates (AKP) activity, lysozyme (LSZ) contents, superoxide dismutase (SOD)activity, catalase (CAT) activity, total antioxidant capacity (T-AOC) activity,malondialdehyde (MDA) content and HSP70expression were significantlyinfluenced by chronic nitrous nitrogen exposure.1) After exposed in differentconcentrations (0.12-2.30mg/L) of nitrous nitrogen, the ACP, AKP, T-AOC activityand LSZ content in the body wall of sea cucumber peaked at beginning period in theexperiment. The ACP, AKP, SOD activity and the LSZ content of the body wall in the57.50mg/L nitrous nitrogen exopsure treatment was significantly lower than that inthe control group when the sea cucumbers were exposed in nitrous nitrogen in day20.2) The SOD and CAT activity in the body wall increased significantly in lowconcentration (0.12-2.30mg/L) nitrous nitrogen exposure, while the SOD and CATactivity in the body wall decreased significantly at high nitrous nitrogenconcentrations (11.50-57.50mg/L) exposure.3) The MDA content in the body wallincreased in all nitrous nitrogen concentration exposure treatment during theexperiment, with higher MDA content in more concentrated nitrous nitrogen sea water.4) The HSP70content peaked at the beginning period of the experiment, and thendecreased gradually to a steady expression level. The maximum expression of HSP70in sea cucumber body wall was positively correlated with the concentration ofambient nitrous nitrogen. The results of this study indicated that the immunoenzyme of the sea cucumber protected itself initiatively at low nitrous nitrogen concentration(<2.30mg/L) exposure, while the immunity of sea cucumber decreased significantlyat relatively high nitrous nitrogen concentration exposure.5) The HSP70expressionin the body wall could be a sensitive indicator of the ambient nitrous nitrogen stress inthe sea cucumber aquaculture.3. Effect of acute nitrous nitrogen exposure on immune responses and heatshcok protein70expression in A. japonicus: The effect of different ambient nitrousnitrogen concentrations (79.43,128.82,208.93,338.84,549.54and891.25mg/L)exposure on non-specific immune response and heat shock protein70(HSP70)expression of the body wall in A.japonicus (wet weight (48.96±0.88) g) was studiedby experimental ecology method. The results showed that the acid phosphatase (ACP)activity, alkaline phosphates (AKP) activity, lysozyme (LSZ) contents, superoxidedismutase (SOD) activity, catalase (CAT) activity, total antioxidant capacity (T-AOC)activity, malondialdehyde (MDA) content and HSP70expression were significantlyinfluenced by acute ambient nitrous nitrogen exposure. After exposed in differentnitrous nitrogen concentrations (128.82-891.25mg/L) sea water, the ACP, AKP,T-AOC activity and LSZ content in the body wall of the sea cucumber peaked atbeginning period of the experiment. The SOD and CAT activity in the body wallincreased significantly in low nitrous nitrogen concentration (79.43-128.82mg/L)exposure, and decreased significantly in high nitrous nitrogen concentration(208.93-891.25mg/L) exposure. The MDA content in the body wall increased in allnitrous nitrogen concentration exposure treatment during the experiment, with higherMDA content in more concentrated nitrous nitrogen sea water. The HSP70expressionpeaked firstly, and then decreased gradually to a steady expression level. Themaximum expression of HSP70in body wall of the sea cucumber was positivelycorrelated with the concentration of nitrous nitrogen in the sea water.4. The effect of chronic and acute nitrous nitrogen exposure on isozymes ofA. japonicus: Esterase (EST), malate dehydrogenase (MDH) and superoxide dismutase (SOD) isozyme expression in different tissues, i.e., the body wall,respiratory tree and intestine of the sea cucumber (wet weight (48.96±0.88) g)which was exposed in nitrous nitrogen sea water were determined by the method ofvertical polyacrymide gel electrophoresis. The results showed that the expression ofEST, MDH and SOD isoenzyme of sea cucumber A. japonicus was siginifcantlydifferent in the body wall, respiratory tree and intestine. The expression of ESTisoenzyme due to the nitrous nitrogen exposure was more complex than that of MDHand SOD isoenzyme. The sea cucumber stressed by nitrous nitrogen exhibitedstronger anaerobic metabolism and weaker aerobic metabolism, which resulted indecline in the immunity of the sea cucumber, and subsequently resistance to thedeleterious environment. |
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