摘要或動機

重金屬對人體傷害的無遠弗屆-人人皆知，根據流行病學的研究指出，長期處\r
在重金屬含量過高之地區，易造成生理病變。比方說，長期生活在砷含量高的環境\r
中，易導致肝臟、周邊血管及神經系的損害，各種癌症的發生機率也大為提高；長\r
期處在含量過高的鎘環境中，易引起不正常的鈣代謝﹐產生骨質疏鬆症、軟骨症、\r
糖尿、胺基尿酸、尿蛋白、貧血、和肝功能異常的症狀；而目前坊間所看到各類茶\r
品中含有的兒茶素則被發現具有抗氧化、抗突變及清除自由基等功能。故本實驗以\r
人類胃癌細胞(SC-M1)為材料，以微核(micronuclei)偵測技術觀察細胞長期處理兒茶\r
素((-)-epigallocatechin-3-gallate, EGCG)後，對於亞砷酸鈉(sodium arsenite, NaAsO?)\r
及氯化鎘(cadmium chloride, CdCl?)所造成的細胞遺傳毒性有何影響。另一方面則利\r
用SRB 分析法測量細胞存活率，探討長期處理兒茶素後，亞砷酸鈉及氯化鎘對於細\r
胞的毒殺情況是否改變。實驗結果顯示細胞長期處理兒茶素不會造成微核的增加，\r
但是卻會增加細胞的存活率；單獨處理亞砷酸鈉和氯化鎘則都會使細胞中微核明顯\r
的增加，且會降低細胞的存活率；而長期處理兒茶素的細胞對亞砷酸鈉所誘發的微\r
核有抑制作用且會增加細胞對於亞砷酸鈉的耐受度，長期處理兒茶素無法抑制氯化\r
鎘所誘發的微核與細胞毒性。\r
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It is well documented that exposure to heavy metals could cause seriously adverse\r
effects to humans. Epidemiological evidence has shown that illness is frequently\r
observed in residents living long-term in heavy metal contaminated area. For example,\r
long-term exposure of arsenic was associated with increased incidences of liver diseases,\r
peripheral vascular and neurological diseases, as well as cancers. And long-term exposed\r
to cadmium may lead to abnormal metabolism of calcium, osteoporosis, osteomalacia,\r
glucouria, aminoaciduria, proteinuria, anemia and abnormal liver function. Recently,\r
numerous reports have shown that (-)-epigallocatechin-3-gallate (EGCG), the major\r
polyphenol from green tea, have ability to anti-oxidative stress and anti-mutagenesis. In\r
this report, we investigated the effects of EGCG long-term exposure in sodium arsenite\r
and cadmium chloride induces chromosomal damages and cytotoxicity in a gastric cancer\r
cell line, SC-M1. Our present results demonstrated cells long-term exposure to EGCG did\r
not induce micronuclei (MN) formation but induce the growth rate. Sodium arsenite or\r
cadmium chloride alone significantly induced MN formation and cytotoxicity in cells\r
without long-term EGCG exposure. However, long-term treatment of SC-M1 cells with\r
EGCG significantly reduced MN formation and protects the cells from cytotoxicity\r
induced by arsenite. Long-term exposure of EGCG had no effect on MN induction and\r
cell survival in cadmium-treated SC-M1 cells.