本研究主要探討飼料中缺鋅對吳郭魚 (Oreochromis niloticus x O. aureus) 各組織的細胞色素P4501A (cytochrome P4501A, CYP1A) 活性及表現之影響。吳郭魚分別以含5 ppm (缺鋅組, zinc-deficiency group ) 及46 ppm (對飼組, pair-fed control) 鋅的飼料飼養8週。發現兩組吳郭魚的增重率、肝體比沒有明顯差異，但缺鋅組之吳郭魚血漿中的鋅濃度則明顯低於對飼組。各組織中之CYP含量及ethoyresorufin-O- deethylase (EROD)、NADPH-cytochrome C reductase的活性亦無明顯差異。進一步將此二組的吳郭魚分別施打五氯酚 (pentachlorophenol, PCP)，則發現吳郭魚肝臟、鰓、腎臟、脾臟及腸組織中EROD 之活性均可被PCP誘發。但經注射PCP後的缺鋅組之吳郭魚之肝臟、鰓、腎臟之EROD活性明顯比對飼組為低。同時以即時定量反轉錄聚合酶連鎖反應分析 (real-time quantitative reverse transcription PCR) 進行CYP1A mRNA表現量的分析，發現缺鋅組之吳郭魚的肝臟、鰓、腎臟、脾臟等組織CYP1A mRNA的表現量與對飼組比較明顯較低。我們推測顯示鋅的缺乏會減少吳郭魚CYP1A mRNA的表現量，鋅在CYP1A調控上可能具有重要的功能。 The present study investigated the effect of dietary zinc deficiency on cytochrome P4501A (CYP1A) activity and expression in different tissues of tilapia. The fish were fed diets containing 5 ppm (zinc-deficient dietary group) and 46 ppm (pair-fed control) for 8 weeks. Compared with the pair-fed control, zinc deficiency reduced plasma zinc concentration but no effect on the body weight gain, hepatosomatic index. CYP content, NADPH-cytochrome C reductase and ethoxyresorufin-O-deethylase (EROD) were also not affected by dietary zinc deficiency. The fish of each dietary group was further injected individually with pentachlorophenol (PCP), CYP1A-mediated EROD activities and levels of CYP1A mRNA were determined. EROD was significantly inducible by PCP in the liver, gill, kidney, spleen and intestines of tilapia. Compared with the pair-fed control, zinc deficiency reduced the PCP-induced EROD activities in the liver, gill, and kidney of tilapia. Moreover, Real-time quantitative reverse transcription PCR assay revealed an inhibition of CYP1A mRNA expression in the liver, gill, kidney and spleen of the zinc-deficient tilapia. We concluded that the fact that dietary zinc deficiency reduced the gene expression of the CYP1A in tilapia. It is possible that zinc could have the important function in the regulation of CYP1A gene.
