大黄素、维生素C及其配伍对团头鲂抗拥挤胁迫的影响

EFFECTS OF EMODIN,VITAMIN C AND THEIR COMBINATION ON CROWDING STRESS RESISTANCE OF WUCHANG BREAM (MEGALOBRAMA AMBLYCEPHALA YIH)

选取1200尾健康的团头鲂(Megalobrama amblycephala Yih),体重为(133.44±2.11)g,随机分成4组,其中1组为对照组,投喂基础日粮(含50.3 mg/kg维生素C,以L-抗坏血酸-2-多聚磷酸酯为Vc源),另外3组为试验组,投喂饲料是在基础日粮中分别添加60 mg/kg大黄素、700 mg/kg Vc、60 mg/kg大黄素+700 mg/kg Vc。饲养60d后,从各池中取25尾规格基本一致的鱼,进行连续48h的拥挤胁迫(100 g/L)实验,分别于0h、12h、24h、48h取样分析团头鲂血液和肝脏的生化指标以及肝脏两种HSP70s mRNA的表达水平,并统计各组鱼的累积死亡率。结果表明,在拥挤胁迫前,与对照组相比,大黄素、Vc组显著提高了团头鲂血清总蛋白(TP)、溶菌酶(LSZ)和碱性磷酸酶(AKP)的水平,肝脏超氧化物歧化酶(SOD)的活性和诱导型HSP70 mRNA的表达水平,降低了血清皮质醇(COR)、甘油三酯(TG)以及肝脏丙二醛(MDA)的含量(P<0.05),且大黄素组还显著提高了肝脏过氧化氢酶(CAT)的活性(P<0.05);配伍组虽然血清TP、LSZ以及肝脏HSP70 mRNA的水平显著升高,肝脏MDA的含量也显著降低(P<0.05),但均未表现出协同增效作用。在拥挤胁迫后,与对照组相比,大黄素、Vc组不同程度地提高了团头鲂血清TP和AKP的水平,肝脏SOD和CAT的活性以及HSC70和HSP70 mRNAs的表达水平,降低了血清COR、葡萄糖(GLU)、谷丙转氨酶(GPT)、谷草转氨酶(GOT)、TG以及肝脏MDA的水平,而LSZ活性表现为先下降后升高;在配伍组中,这些指标虽然有类似以上的变化趋势,但大多差异不显著(P>0.05),且同样未表现出协同增效作用。统计表明,大黄素和Vc组鱼的累积死亡率在拥挤胁迫24h、48h均显著低于对照组(P<0.05),而配伍组与对照组的差异均不显著(P>0.05)。由此可见,在基础日粮中添加大黄素60 mg/kg或Vc 700 mg/kg,可提高团头鲂的非特异性免疫力、抗氧化能力以及两种HSP70s mRNA的表达水平,增强鱼体的抗应激能力。二者配伍则效果不佳,其相互作用的机理还有待于进一步研究。

This study aims to evaluate the effects of dietary emodin,high-dose vitamin C（Vc） and their combination on non-specific immunity and stress prevention of Wuchang bream,Megalobrama amblycephala Y.,subjected to crowding stress.1200 healthy fish with initial body weight of（133.44±2.11） g were selected and randomly divided into four groups： one was the control group fed with basal diet（containing Vc 50.3 mg/kg,with the L-ascorbyl-2-polyphosphate as Vc source）,the three treated groups were fed with basal diets supplemented with emodin 60 mg /kg,Vc 700 mg/kg,and the combination of emodin 60 mg/kg ＋ Vc 700 mg/kg,respectively.After feeding for 60 days,25 fish per tank were exposed to crowding stress（100 g/L） for 48h,the biochemical parameters of blood and liver,liver two heat shock pro-tein 70s（HSP70s） mRNA levels,and cumulative mortalities of fish in each group were investigated at 0h,12h,24h and 48h,respectively.The results showed that,before crowding stress,compared with the control,serum total protein（TP）,lysozyme（LSZ） and alkaline phosphatase（AKP） levels,liver superoxide dismutase（SOD） activity and expression level of inducible HSP70 mRNA increased significantly in emodin and Vc groups while serum cortisol（COR）,triglyceride（TG） and liver malondialdehyde（MDA） contents decreased（〈P0.05）;liver catalase（CAT） activity also significantly increased in emodin group（P〈0.05）.Although serum TP,LSZ,and liver HSP70 mRNA levels significantly increased and liver MDA level decreased in combination group（P〈0.05）,no synergism was observed.After crowding stress,compared with the control,the serum TP and AKP levels,liver SOD and CAT activities,and expression levels of HSC70 and HSP70 mRNAs increased in emodin and Vc groups in varying degrees and serum COR,glucose（GLU）,glutamic-pyruvic transaminase（GPT）,glutamic-oxaloacetic transaminase（GOT）,TG and liver MDA levels decreased to some extent,whereas the LSZ activity decreased at first and then increased significantly（P〈0.05）.Although these parameters had similar changing trend as above ones in combination group,it did not show any syner-gism either.Statistics showed that under crowding stress,the cumulative mortalities of emodin and Vc groups were sig-nificantly lower than that of control group at 24h and 48h（P〈0.05） while the difference between the combination and control groups was not significant（P〉0.05）.Therefore,the basal diet supplemented with emodin 60 mg/kg or Vc 700 mg/kg could improve non-specific immunity of fish,antioxidant capacity,and two HSP70s mRNA expression levels,and enhance resistance to crowding stress.However,the combination of emodin and high-dose Vc showed no better effect,the mechanism of their interaction needs further study.