Ueng Y F, Ueng T H
Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Republic of China.
Arch Biochem Biophys. 1995 Oct 1;322(2):347-56. doi: 10.1006/abbi.1995.1474.
Pretreatments of freshwater fish tilapia, Oreochromis niloticus x O. aureus, with 3-methylcholanthrene (3-MC) and polychlorinated biphenyls (PCBs) increased liver microsomal cytochromes P450 (P450) and b5 contents, benzo[a]pyrene hydroxylation, and 7-ethoxyresorufin and 7-ethoxycoumarin O-dealkylations. The pretreatments also increased gill microsomal benzo[a]pyrene and 7-ethoxyresorufin oxidations. Immunoblot analysis of liver and gill microsomes revealed that 3-MC and PCBs induced a protein recognized by the mouse monoclonal antibody (MAb) 1-12-3 against scup P450 1A1. Northern analysis of liver and gill RNA showed that 3-MC and PCBs increased the intensity of 2.9-kb- and 1.5-kb-sized mRNA bands hybridizable to a trout P450 1A1 cDNA probe. Pretreatment with phenobarbital was without effects on the monooxygenase activity or protein or mRNA levels in liver and gill. A 3-MC-inducible P450 hemoprotein (M(r) = 59,000) and a NADPH-cytochrome P450 reductase flavoprotein (M(r) = 74,000) were purified from liver microsomes. The tilapia P450 hemoprotein showed an absorption maximum at 447 nm in CO-difference spectrum and a strong immunoreactivity with MAb 1-12-3. A reconstituted tilapia monooxygenase system consisting of P450 and NADPH-cytochrome P450 reductase was effective in the catalysis of 7-ethoxyresorufin, benzo[a]pyrene, and 7-ethoxycoumarin oxidations, but not in N-nitrosodimethylamine demethylation. These results show that 3-MC and PCBs can induce P450 1A1 in tilapia liver and gill and the tilapia P450 is highly similar to other teleost P450 1A1 with respect to spectral, immunochemical, and catalytic properties.
用3-甲基胆蒽（3-MC）和多氯联苯（PCBs）对淡水鱼罗非鱼（尼罗罗非鱼×奥利亚罗非鱼）进行预处理，可增加肝脏微粒体细胞色素P450（P450）和b5的含量、苯并[a]芘的羟化作用以及7-乙氧基试卤灵和7-乙氧基香豆素的O-脱烷基作用。预处理还增加了鳃微粒体中苯并[a]芘和7-乙氧基试卤灵的氧化作用。对肝脏和鳃微粒体进行免疫印迹分析显示，3-MC和PCBs诱导产生了一种可被针对鲷鱼P450 1A1的小鼠单克隆抗体（MAb）1-12-3识别的蛋白质。对肝脏和鳃RNA进行Northern分析表明，3-MC和PCBs增加了可与鳟鱼P450 1A1 cDNA探针杂交的2.9 kb和1.5 kb大小mRNA条带的强度。用苯巴比妥预处理对肝脏和鳃中的单加氧酶活性、蛋白质或mRNA水平没有影响。从肝脏微粒体中纯化出一种3-MC诱导型P450血红素蛋白（相对分子质量=59,000）和一种NADPH-细胞色素P450还原酶黄素蛋白（相对分子质量=74,000）。罗非鱼P450血红素蛋白在CO差光谱中的最大吸收峰位于447 nm，并且与MAb 1-12-3具有强烈的免疫反应性。由P450和NADPH-细胞色素P450还原酶组成的重组罗非鱼单加氧酶系统可有效催化7-乙氧基试卤灵、苯并[a]芘和7-乙氧基香豆素的氧化作用，但不能催化N-亚硝基二甲胺的脱甲基作用。这些结果表明，3-MC和PCBs可诱导罗非鱼肝脏和鳃中的P450 1A1，并且罗非鱼P450在光谱、免疫化学和催化特性方面与其他硬骨鱼P450 1A1高度相似。
