亚硝酸盐胁迫对罗氏沼虾血细胞及其抗氧化酶活力的影响

【背景】亚硝酸盐是虾类集约化养殖过程中最常见的毒性污染物之一,研究亚硝酸盐胁迫对罗氏沼虾血细胞的毒性以及抗氧化酶在抗胁迫防御中的作用,能够为罗氏沼虾养殖过程中的亚硝酸盐中毒防治提供理论参考。【方法】以不同浓度(0、1、5和10 mg·L~(-1))的亚硝态氮(NO_2~--N)对罗氏沼虾进行胁迫,于胁迫后的0、6、12、24和48 h取样,应用流式细胞术检测血细胞活性氧(ROS)含量和细胞凋亡率,同时测定血细胞总数(THC)和胞内抗氧化酶活力。【结果】1 mg·L~(-1)NO_2~--N在48 h内对血细胞ROS含量、凋亡率和THC均无显著影响。5 mg·L~(-1)NO_2~--N胁迫24 h,血细胞ROS含量显著上升,THC显著下降,胁迫48 h凋亡率显著提高。10 mg·L~(-1)NO_2~--N胁迫6 h,血细胞ROS含量和凋亡率均显著上升,胁迫12 h THC显著下降。血细胞的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GPx)的活力均不同程度地被NO_2~--N胁迫所诱导,CAT活力主要在胁迫前期提高,而GPx活力在胁迫后期提高。【结论与意义】亚硝酸盐存在浓度和时间毒性效应,一定浓度的亚硝酸盐会诱导虾血细胞产生ROS,这些ROS的过量产生诱导了血细胞发生凋亡,继而导致THC下降,这一氧化胁迫过程可能是亚硝酸盐对罗氏沼虾产生细胞毒性的重要机制之一。抗氧化酶活力的诱导表明抗氧化酶在亚硝酸盐胁迫过程中发挥防御作用。

Effects of nitrite on haemocyte and antioxidant enzyme activity in Macrobrachium rosenbergii

Background] Nitrite is one of the most common pollutants in intensive shrimp aquaculture. In order to provide theoretical basis of nitrite prevention and cure for culture of Macrobrachium rosenbergii, we investigated the toxicity effects of nitrite on M. rosenbergii haemocytes, and the role of antioxidant enzymes in anti-nitrite defense.Method] Prawns were exposed to different doses (0, 1, 5 and 10 mg·L^-1) of NO₂^--N. Reactive oxygen species (ROS) production in haemocytes and apoptotic haemocyte ratio were determined by flow cytometry. The total haemocyte count (THC) and intracellular antioxidant enzyme activities were also analysed after 0, 6, 12, 24 and 48 h exposure.Result] Results showed that 1 mg·L^-1 NO₂^--N had no significant effect on ROS production, apoptotic cell ratio and THC. Increase of ROS production and decline of THC could be observed in prawn exposed to 5 mg·L^-1 NO₂^--N after 24 h, and increase of apoptotic ratio occurred after 48 h. Increase of both ROS production and apoptotic ratio were observed in prawn exposed to 10 mg·L^-1 NO₂^--N after 6 h, and THC decreased after 12 h. Superoxide dismutase (SOD), catalase (CAT), and glutathion peroxidase (GPx) activities in haemocytes were induced by NO₂^--N to different levels.Conclusion and significance] These results clearly demonstrate the dose-and time-dependent toxic effect of nitrite. They also indicate that nitrite could induce the ROS generation in prawn haemocytes and then the overproduction of ROS causeing haemocyte apoptosis and subsequent THC decline. This process of oxidative stress is one of the cytotoxicity mechanisms of nitrite on M. rosenbergii. The induced activities of antioxidant enzymes indicate that these antioxidant enzymes play a vital role in anti-nitrite defence.