超氧化物歧化酶(superoxide dismutase,SOD,EC1.15.1.1)是广泛存在于生物体的重要抗氧化酶之一,在抵御过多活性氧簇(reactive oxygen species,ROS)对机体毒害的过程中起重要作用。本研究采用RT-PCR及RACE方法,从草鱼(Ctenopharyngodon idellus)肝胰脏中克隆了Cu/Zn-SOD全长c DNA。该Cu/Zn-SOD c DNA(Gen Bank登录号:GU901214)全长725 bp,包括完全开放阅读框(ORF)465 bp,5’端非编码区(5’-UTR)为18 bp,3’-UTR为242 bp。其ORF编码154个氨基酸,分子量约为15.93 k D,理论等电点为5.57。序列比较表明,草鱼Cu/Zn-SOD c DNA的推测氨基酸序列与其它多种动物的一致性较高,其一致性为57.8%~96.8%;同时,具有Cu/Zn-SOD家族保守的4个Cu2+结合位点即组氨酸H-47、-49、-64、-121和4个锌离子结合位点即H-64、-72、-81及天冬氨酸D-84,一对二硫键即两个半胱氨酸残基C-58、-147及蛋白家族标签序列45'GFHVHAFGDNT'55与139'GNAGGRLACGVI'150。应用实时荧光定量PCR检测了草鱼Cu/Zn-SOD m RNA组织表达特征。结果显示,Cu/Zn-SOD m RNA在草鱼在11种组织器官内均有表达,但不同组织之间差异很大;其中在肝胰脏Cu/Zn-SOD m RNA的表达水平最高,显著高于其它组织(p<0.05),而在脂肪中表达丰度最低(p<0.05)。该研究结果将有助于进一步探讨鱼类Cu/Zn-SOD基因的结构与功能,并为研究其抗氧化分子机理奠定基础。
Concentrations of lead( Pb),cadmium( Cd),chromium( Cr),copper( Cu),zinc( Zn) and manganese( Mn) were measured in various organs( such as in liver and muscle) from 9 species of freshwater economic fishes which were collected from northeast area of Guangdong Province. The concentration of metals was measured by inductively coupled plasma atomic emission spectrometry( ICP- AES). Results showed that the levels of metals in hepatopancreas of the fishes were found in order of Zn > Pb > Cu > Hg > Cd,while in muscles were Zn > Cr> Pb > Mn > Cu > Cd. In general,the metals concentrations were significantly higher in liver samples than that in muscle samples. Based on the " pollution index of single factor",the fishes,to one degree or another,were polluted by Pb,Cd,Cr,Cu and Zn,and pollution levels were mostly followed by Pb > Cd > Cr > Cu > Zn. The indexes of Pb and Cd tested in hepatopancreas of the fishes were in a majority exceeded the national safety criteria for food in China. What's more,it was found that the contents of the heavy metals in fishes did not vary with the trophic level which they belong to. In summary,the fishes were polluted by Pb,Cd,Cr,Cu and Zn to some extent,which indicated that hidden danger of heavy metals pollution was present in ecological environment or safety in fishery production in the area.
The juveniles of hybrid tilapia( Oreochromis niloticus × Oreochromis areus) were exposed to ammonia-nitrogen( N)( 0,2. 5,5,10 and 20 mg / L) for0,12,24,48 and 72 h to evaluate the effect of ammonia-N stress on their non-specific immunity. Results show that the activity of serum lysozyme decreased significantly with extension of stress time( P < 0. 05). The total antioxidant capacity( T-AOC) and activity of antioxidase in liver were significantly affected. The activity of T-AOC and total superoxide dismutase( T-SOD) of fish exposed to ammonia-N were initially decreasing then increasing( P < 0. 05). Activities of catalase( CAT) and glutathione peroxidase( GSH-Px) were correlated with concentrations of ammonia-N. Fish exposed to lower concentrations( 2. 5 mg/L or 5 mg/L)showed decreased CAT activity within 24 h( P < 0. 05),while those exposed to higher concentrations( 10 mg / L or 20 mg / L) initially showed increased then decreased activity of CAT. Except for the highest concentration groups,fish exposed to ammonia-N showed inductive activity of GSH-Px( P < 0. 05). Under the experimental conditions,non-specific immunity of tilapia was affected by ammonia-N stress,and the impact was increased with increased concentration and extension of time.
