聚β-羟基丁酸酯对凡纳滨对虾(Litopenaeus vannamei)非特异性免疫力及氨氮胁迫后免疫基因表达量的影响

Effects of Poly-β-Hydroxybutyrate on Non-Specific Immunity and Expression of Immune Gene Under the Ammonia Stress of Litopenaeus vannamei

中文关键词: 凡纳滨对虾  聚β-羟基丁酸酯  免疫因子  酶活力  RT-PCR

英文关键词: Litopenaeus vannamei  Poly-β-hydroxybutyrate  Immune factor  Enzyme activity  RT-PCR

中文摘要:

      以凡纳滨对虾(Litopenaeus vannamei)为研究对象，探讨饲料中添加聚β-羟基丁酸酯(Poly-β-hydroxybutyrate, PHB)对其非特异性免疫能力的影响。采用单因子浓度梯度法，在基础饲料中分别添加1.0%、2.5%和5.0%的PHB配制成实验饲料，饲喂21 d后测定对虾免疫酶活性，选择最佳浓度组与空白对照组进行氨氮胁迫实验，测定对虾丙二醛(MDA)含量，同时利用RT-PCR技术测定氨氮胁迫48 h内对虾免疫基因表达水平，观察PHB对免疫基因表达量的影响。结果显示，总抗氧化能力(T-AOC)随PHB浓度升高呈现先上升后下降的趋势，血液、肝胰腺及鳃丝中T-AOC分别在2.5%、2.5%及1.0% PHB浓度时达到最高；PHB对肝胰腺中超氧化物歧化酶(SOD)活力无显著影响，血淋巴及鳃丝中SOD活力在最高浓度组(5.0% PHB)与对照组之间差异显著(P<0.05)；过氧化物酶(POD)和溶菌酶(LZM)在鳃和肝胰腺中的活力于PHB浓度为1.0%和2.5%时达到最高，其中POD相对于对照组分别提高了7.63倍和0.68倍，LZM活力分别提高了0.88及0.18倍。氨氮胁迫实验结果显示，对虾经PHB饲喂后，体内免疫基因表达量高于对照组，且体内MDA含量低于对照组。综上结果说明，PHB能提高凡纳滨对虾非特异性免疫能力。

英文摘要:

      Poly-β-hydroxybutyrate (PHB) is a polymer of the short-chain fatty acid β-hydroxybutyrate. β-hydroxybutyric acid facilitates food digestion, absorption, and the protein and mineral utilization. The bacteria-derived PHB can be potentially used as an alternative to the conventional antibiotics in aqua-farming. Here we explored the effects of PHB on non-specific immunity of Litopenaeus vannamei. The L. vannamei was fed with baits containing PHB at different concentrations (0, 1.0%, 2.5% and 5.0%). The enzyme activities of the total antioxidant capacity (T-AOC), superoxide dismutase (SOD), peroxidase (POD) and lysozyme (LZM) in gill, hepatopancreas and serum were analyzed and compared among groups. The group with the best performance and the control group were selected for the ammonia stress test. After the NH4Cl treatment, we measured the concentration of malonaldehyde (MDA) and the expression levels of related genes in tissues by using real-time PCR. The results suggested that PHB affected the congenital immunity in the shrimp. As the concentration of PHB increased, the T-AOC activity in the experimental groups was first elevated followed by a decline. The activities of T-AOC in the serum, the hepatopancreas and the gill reached the maximum when the concentration of PHB was 2.5%, 2.5% and 1.0% respectively. The SOD activity in the gill and serum of shrimp fed with 5.0% PHB was significantly different from that in the control group. In the gill and hepatopancreas, the activity of POD and LZM peaked when the PHB concentration was 1.0% and 2.5% respectively. Compared with the control group, the POD activities of the experiment group supplemented with 1.0% and 2.5% PHB were 7.63-fold and 0.68-fold in the gill and hepatopancreas, and LZM activities were 1.88-fold and 1.18-fold, respectively. After the ammonia stress test, the shrimp fed with PHB showed lower MDA concentration than that without PHB, and the difference was significant in the serum (P<0.05). Furthermore, the expression levels of related genes were higher in the experimental groups compared to the control group. Our data indicated that PHB could improve non-specific immunity of shrimps.