氨氮慢性胁迫对凡纳滨对虾肝胰腺氨代谢相关指标及细胞凋亡的影响

Effects of chronic ammonia nitrogen stress on indexes related to ammonia metabolism and apoptosis in hepatopancreas of Litopenaeus vannamei

  • 摘要: 【目的】探究在盐度3下氨氮慢性胁迫对凡纳滨对虾(Litopenaeus vannamei)氨代谢和细胞凋亡的影响,以期为凡纳滨对虾免疫机理研究和生产实践指导提供参考。【方法】将480尾初始体质量6.49±0.14 g的凡纳滨对虾分为4个组,6个平行,暴露于0(对照组)、0.9、5.2和12.0 mg/L的氨氮水体中,氨氮胁迫20和40 d后分别统计凡纳滨对虾体质量增长率和存活率,测定凡纳滨对虾血淋巴和肝胰腺中氨代谢相关物质和酶活性、抗氧化酶活性及细胞凋亡相关基因表达量,同时取肝胰腺制作石蜡切片进行Tunnel染色。【结果】随氨氮浓度增加,体质量增长率和存活率逐渐降低,血淋巴氨氮和尿素氮含量逐渐升高,胁迫20 d与胁迫40 d结果相近;肝胰腺谷氨酸脱氢酶(GDH)、谷氨酰胺合成酶(GS)和过氧化氢酶(CAT)活性在氨氮胁迫20 d升高,在氨氮胁迫40 d时5.2和12.0 mg/L组酶活性降低;氨氮胁迫20 d,12.0 mg/L组的肝胰腺总超氧化物歧化酶(T-SOD)活性显著低于对照组(P<0.05,下同);各胁迫组肝胰腺Cyt CCaspase-3基因表达量显著高于对照组。TUNEL检测结果显示,细胞凋亡数量随氨氮浓度增加而增加,且氨氮胁迫40 d较20 d更多。【结论】经氨氮慢性胁迫后,环境氨氮扩散到血淋巴中,凡纳滨对虾血淋巴氨氮累积越多,尿素氮含量随之增加,肝胰腺谷氨酰胺合成途径受到抑制,氨代谢受到阻碍,应激产生的活性氧超出抗氧化系统调节范围,对肝胰腺造成损伤,诱导细胞凋亡发生,对凡纳滨对虾生长存活造成不利影响。

     

    Abstract: 【Objective】 To study effects of chronic ammonia nitrogen stress on ammonia metabolism and apoptosis of Litopenaeus vannamei under three salinities, in order to provide reference for the study of immune mechanism and production of L. vannamei.【Method】 480 healthy L. vannamei with initial body mass of 6.49±0.14 g were randomly divided into 4 groups, 6 of which were exposed to 0 (control group), 0.9, 5.2 and 12.0 mg/L ammonia nitrogen. After 20 and 40 d of ammonia nitrogen stress, the body weight growth rate and survival rate of L. vannamei were calculated, and ammonia metabolism-related substances and enzyme activity, antioxidant-related enzyme activity and expression of apoptosisrelated genes in hemolymph and hepatopancreas of L. vannamei were determined. Meanwhile, the hepatopancreas were taken to make paraffin section and stained with Tunnel.【Result】 With the increase of ammonia nitrogen concentration, the growth rate and survival rate of body mass decreased, ammonia nitrogen and urea nitrogen in hemolymph and the indexes in 20 d were similar with those in 40 d;glutamate dehydrogenase(GDH) activity, glutamine synthetase(GS) activity and catalase(CAT) activity in hepatopancreas increased at 20 d, and decreased in 5.2 and 12.0 mg/L group at 40 d;total superoxide dismutase(T-SOD) activity of hepatopancreas was significantly lower in the 12 mg/L group than that in the control group(P<0.05, the same below);expression of Cyt C and Caspase-3 of hepatopancreas was significantly higher in the stress group than that in the control group. The results of TUNEL showed that the number of apoptotic cells increased with the increase of ammonia nitrogen concentration, and the number of apoptotic cells was higher at 40 d than that at 20 d.【Conclusion】 After chronic ammonia nitrogen stress, as ammonia nitrogen in environment spreads to hemolymph, with more and more ammonia nitrogen accumulated in hemolymph of L. vannamei, urea-nitrogen content increased, then the pathway of L-glutamine synthesis is inhibited, so ammonia metabolism is hindered. Here reactive oxygen species(ROS) stemmed from stress overwhelms regulation ability of antioxidant system, which poses damages to hepatopancreas, leading to apoptosis, causing negative impact to growth and survival of L. vannamei.

     

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