大黄素、维生素C及其配伍对团头鲂感染嗜水气单胞菌后生理生化指标的影响

Effects of emodin,vitamin C and their combination on biochemical parameters and two HSP70s mRNA expression of Wuchang bream (Megalobrama amblycephala) infected with Aeromonas hydrophila

为综合评价大黄素、高剂量维生素C及其配伍对团头鲂(Megalobrama amblycephala Yih)抗嗜水气单胞菌感染能力的影响,选取1 200尾健康的团头鲂,体质量为(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,另外3组在基础日粮中分别添加60 mg/kg大黄素、700 mg/kg维生素C、60 mg/kg大黄素+700 mg/kg维生素C(配伍组)。饲养60 d后,经腹腔注射感染嗜水气单胞菌,并在攻毒前后检测团头鲂血液和肝脏的生化指标以及肝脏2种热休克蛋白70s(HSP70s)mRNA的表达水平;另从各池中取10尾鱼进行同样的攻毒试验,统计攻毒后各时间点鱼的累积死亡率。结果表明,攻毒后,与对照组相比,大黄素、维生素C组不同程度地提高了血清总蛋白(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)和过氧化氢酶(CAT)的活性以及HSC70和HSP70 mRNA的表达水平,降低了血清皮质醇(COR)、血糖(GLU)、谷丙转氨酶(GPT)、谷草转氨酶(GOT)、甘油三酯(TG)以及肝脏丙二醛(MDA)的水平;配伍组中,这些指标的变化趋势虽与上述类似,但大多与对照组的差异不显著(P>0.05),且未表现出协同增效作用。此外,各组鱼血清胆固醇(CHOL)的含量在攻毒前后的差异均不显著(P>0.05)。统计也表明,大黄素和维生素C组鱼的累积死亡率在攻毒后24 h、48 h均显著低于对照组(P<0.05),而配伍组试验鱼的累积死亡率与对照组差异均不显著(P>0.05)。由此可见,在基础日粮中添加大黄素60 mg/kg或维生素C 700 mg/kg,可提高鱼体的非特异性免疫力、抗氧化能力以及2种HSP70s mRNA的表达水平,增强鱼体抗病原菌感染的能力。二者配伍则效果不佳。

The study aims to evaluate the effects of dietary emodin, high-dose vitamin C （Vc） and their combination on the disease resistance of Wuchang bream （Megalobrama amblycephala） against Aeromonas hydrophila infection. One thousand and two hundred 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 other three were the treatment groups, 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 consecutive feeding for 60 days, fifteen fish taken from each tank were intraperitoneally infected with A. hydrophila （BSK-10）, and the biochemical parameters of serum and liver, the mRNA levels of two heat shock protein 70s （HSP70s） in liver before and after infection were determined. Another ten fish taken from each tank were challenged with A. hydrophila using the same method as above, and the cumulative mortality of each group was counted at different time of post-infection. The results showed that before infection, compared with the control group, serum total protein （TP）, lysozyme （LSZ） and alkaline phosphatase （AKP） levels, liver superoxide dismutase （SOD） activity and expression level of inducible HSP70 mRNA significantly increased in emodin and Vc groups, while serum cortisol （COR）, triglyceride （TG） and liver malondialdehyde （MDA） contents decreased （P 〈0.05） in emodin and Vc groups; the liver catalase （CAT） activity also significantly increased in emodin group （P 〈0.05）. Although the serum TP, LSZ and liver HSP70 mRNA levels significantly increased in combination group, and the liver malondialdehyde （MDA） level was also significantly reduced （P 〈0.05）, no synergism was shown.