| 摘要: | 芳香胺類化學致癌物在誘導產生癌症的起始過程中的第一步涉及了此類化學致癌物代謝和活化所產生之活化中間產物，它能夠與標的組織中大分子如DNA結合。芳香胺類化學致癌物的主要代謝途徑是由乙醯轉移酵素催化進行N-乙醯化的產物，乙醯轉移酵素乃是利用乙醯輔媒A當作乙醯基的捐贈者。芳香胺類化學致癌物例如2-aminofluorene經乙醯化變成2-acetylaminofluorene，它可被進一步代謝活化或進行去毒性作用。在人類及許多動物樣本中的乙醯轉移酵素活性已普遍地被檢測，且發現快NAT2乙醯轉移者易導致人類產生大腸直腸和乳癌，而快NAT1和慢NAT2乙醯轉移者易導致人類產生膀胱癌。 於此實驗中我們檢測Indole-3-acetic acid methyl ester對人類膀胱癌細胞株生長的情形，且檢測對人類膀胱癌細胞株、SD大白鼠之白血球以及SD大白鼠之組織中乙醯轉移酵素活性的抑制性，也檢測在SD大白鼠體內2-aminofluorene的代謝情形。結果我們發現Indole-3-acetic acid methyl ester會對人類膀胱癌細胞株造成細胞毒殺性、細胞外型改變、去氧核糖核酸傷害、細胞週期S期的抑制及細胞內cyclins酵素的抑制，且都隨著濃度的增加抑制的程度越明顯。 此外我們發現Indole-3-acetic acid methyl ester會促進老鼠白血球中淋巴球及人類膀胱癌細胞株T-24的NAT活性，且證明NAT活性的增加並非NAT1 基因表現、基因序列及細胞內NAT蛋白的表現受到影響所造成，乃是由於細胞膜破劣使NAT裸露之故。而Indole-3-acetic acid methyl ester則會抑制正常老鼠組織(肝、血液、大腸、膀胱和腎)和人類膀胱癌細胞株T-24細胞質液之NAT活性，且隨著濃度的增加抑制的程度越明顯。而在體內實驗Indole-3-acetic acid methyl ester亦會影響我們所檢測的SD大白鼠組織中NAT對2-AF的代謝及分布情形。; The first step in the initiation process of arylmine carcinogen induced carcinogenesis involves metabolic activation of these carcinogens to reactive intermediate, that are capable of binding to target tissue macromolecules such as DNA. N-acetylation is a major metabolic pathway for arylamine carcinogens which is catalyzed by host cytosolic N-acetyltransferase (NAT), using acetyl coenzyme A as a cofactor. Arylamine, such as 2-aminofluorene (2-AF), are N-acetylated to become 2-acetylaminofluorene, and can undergo further activation or detoxification reations. NAT activity in human and several animal species are genetically determined, and the rapid NAT2 phenotype has been shown to predispose humans to colorectal and breast cancer, whereas the rapid NAT1 and slow NAT2 phenotype are related to arylamine-induced bladder cancer. In this study, Indole-3-acetic acid methyl ester (IAA-Me) was used to determine the cell growth in human bladder cancer cell line (T-24 and TSGH 8301) and inhibition of arylamine NAT activity and Sprague-Dawley (SD) rats’ tissue, and to detect the 2-AF metabolism in SD rat. The results demonstrated that cytotoxicity, DNA damage, morphological change, the inhibition of S phase in cell cycle and intracellular cyclins in T-24 and TSGH 8301 were resulted by IAA-Me, and also in a dose-dependent mannar. And the results demonstrated that NAT activity in intact cells of lymphocytes from normal SD rat’s WBC and T-24 were promoted by IAA-Me because of high extracellular NAT level by cell membrane rupture, but not NAT mRNA levels, sequence mutation, intracellular NAT levels. NAT activity were inhibited in normal SD rat’s tissues (liver, blood, bladder, colon, kidney) and T-24 cytosols by IAA-Me, and the effects also resulted in a dose-dependent mannar. Dietary treatment with Me-IAA to the rat indicate that IAA-Me can affect metabolism of 2-AF and distribution of 2-AF metabolites in SD rat’s different tissues. |
