草鱼幼鱼肝胰脏抗氧化系统对MC-LR胁迫的响应

Oxidative stress response to MC-LR in the hepatopancreas of juvenile grass carp

为了研究微囊藻毒素(MC-LR)对草鱼(Ctenopharygodon idella)幼鱼肝胰脏抗氧化防御系统的影响,本研究通过腹腔注射的方法(剂量为25、100μg MC-LR·kg-1,分别称为低剂量和高剂量),对草鱼幼鱼进行染毒,于胁迫24、48 h和72 h后分离其肝胰脏,随后采用分光光度法检测了草鱼幼鱼肝胰脏中超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性;同时采用荧光定量PCR方法分析了SOD、CAT、谷胱甘肽过氧化物酶(GPx)和谷胱甘肽还原酶(GR)基因相对表达量的变化。结果显示:高剂量MC-LR诱导24 h和48 h后,草鱼幼鱼肝胰脏SOD活性显著增加(P<0.05),而SOD在低剂量组中活性没有显著变化(P>0.05);低剂量MC-LR对CAT活性没有显著影响(P>0.05),而高剂量MC-LR诱导24 h后可使草鱼幼鱼肝胰脏CAT活性显著增加(P<0.05),随后其活性又下降,但差异不显著(P>0.05)。在MC-LR胁迫过程中,SOD、CAT、GPx基因表达在两个剂量组中均显著低于对照组(P<0.05),而GR基因在低剂量MC-LR胁迫24 h后相对表达量显著上调(P<0.05),尽管在72 h相对表达量上调,但差异不显著(P>0.05),而高剂量组中GR基因在胁迫24 h和48 h后,其表达量被抑制,但不存在显著差异(P>0.05)。进行抗氧化酶活性和基因表达相关性分析发现,SOD和CAT酶活性与SOD和CAT基因表达不相关。上述研究表明MC-LR对草鱼幼鱼肝胰脏抗氧化系统产生了明显的胁迫效应,但MC-LR对机体抗氧化酶活性与基因编码调控之间的相互作用机制还有待更深入的研究。

To better understand the influence of microcystin-LR(MC-LR)on the oxidative stress response in the hepatopancreas of juvenile grass carp(Ctenopharyngodon idella), the present study was conducted injecting MC-LR intraperitoneally at doses of 25 μg MC-LR·kg-1(low-dose group)and 100 μg MC-LR·kg-1(high-dose group). Samples of hepatopancreases from juvenile grass carp were collected at24, 48, and 72 h after the initial injection. The activities and transcriptional levels of antioxidant enzymes, including superoxide dismutase(SOD), catalase(CAT), glutathione peroxidase(GPx), and glutathione reductase(GR), were analyzed using spectrophotometry and quantitative real-time PCR, respectively. The enzymatic activity of SOD in the low-dose group was not significantly changed, but its content in the high-dose group was significantly enhanced at 24 and 48 h(P<0.05), while its content began to decrease at 72 h. The enzymatic activity of CAT just in the high-dose groups was significantly enhanced at 24 h(P<0.05), but the activities in the low-and high-dose groups all decreased at 48 h and 72 h with insignificant differences(P>0.05). The expressions of the SOD, CAT, and GPx genes were all significantly down-regulated during the whole experiment(P<0.05), but the expressions of the GR gene in the low-dose group were significantly upregulated just at 24 h(P<0.05); another, its expression in two treated group were also up-regulated at 72 h, but the differences were not significant(P>0.05). However, the expressions of GR gene in the high dose group were all down-regulated with insignificant differences at 24 h and 48 h. In addition, correlation analysis of the enzymatic activities and gene expressions showed that the enzymatic activities of SOD and CAT were not correlated with their gene expressions. This study demonstrated that MC-LR could induce oxidative stress in juvenile grass carp by adjusting enzymatic activity and gene expression, but the mechanism of interaction between these needs to be further studied.