Abstract
本研究藉由低濃度亞砷酸鈉及 BrdU-UV visible ight enrichment 的方 法處理 3x106 經致突變劑 Ethylnitrosourea ( ENU ) 處理過的中國倉 鼠卵巢細胞，並從中篩選出對亞砷酸鈉敏感的細胞株。從全部挑出的 97 個細胞聚落中， 篩選到 14 個對亞砷酸鈉敏感性較 CHO-K1 細胞有 1.5 倍以上的細胞株。並對其中敏感程度穛{較高的兩個細胞株 ( B26 ， D21 ) 作進一步的特性析。由細胞聚落形成法得知，此二株細胞對亞 砷酸鈉敏感的程度分別為 CHO-K1 細胞的3倍以及 7 倍。為了進一步探討 亞砷酸鈉對此二株細胞造成的原因，我們檢查了此二細胞中麩胱甘泩 ( GSH ) 的含量及麩胱甘泩轉移脢 ( GST ) 的活性。雖然 GSH 和 GST 被 証實可能和解除砷化物對細胞造成的毒性有關，但在 B26 及 D21 細胞中 並未發現此二株細胞內 GSH 含量及 GST 的活性和 CHO-K1 細胞有所差異 。另一方面，本研究利用原子吸收光譜法測定細胞受到亞砷酸鈉處理過後 ，細胞內累積砷化物的情形。結果發現，在 D21 細胞受到亞砷酸鈉處理 後， 明顯在細胞中較同樣處理的 CHO-K1 細胞累積較多的砷化物在細胞 之中。同時本實驗也觀察到處理過 25mM SA 的 D21 細胞在不含 SA 的 培養液中一段時間後時間內對砷化物仍有累積較多的情形。在 D21 細胞 的敏感特性方面，以 LD50 而言， 本研究也發現 D21 細胞對 DNA damage agent、 ENU、 順-雙氯雙鉑 ( Cisplatin ) 及伽瑪射線 ( r- ray ) 只有 1.5至 2 倍左右的敏感性。在重金屬方面， D21 細胞對五價 的 sodium arsenate 較 CHO-K1 細胞高 7 倍的敏感性且對氯化汞 ( HgCl2 ) 也較 CHO-K1 細胞高 3 倍的敏感性。 但是對硫酸鋅 ( ZnSO4 ) 及氯化鎘 ( CdCl2 ) 只有 1.5 到 2 倍的敏感性。 A modified cell suicide method was applied to solate the sodium arsenite ( SA ) sensitiveutants from the ethylnitrosourea ( ENU ) mutagenized Chinese hamster ovary (CHO-K1) cells in this study. Totally 197 candidates were picked after screening 3*106 ENU-mutagenized cells and 14 sensitive mutants were obtained from three separated experiments. The most two sensitive sublines, B26 and D21, were about 3- and 7-fold more sensitive to SA than their parental CHO-K1 cells respectively, as estimated from LD50 values. Both the glutathione ( GSH ) level and glutathione s-transferase ( GST ) activity in B26 and D21 cells were equal to those in their parental cells. The D21 cells accumulated more arsenic than CHO-K1 cells did, indicating that the sensitization to SA was related to an increased arsenic accumulation in D21 cells after SA treatment. The D21 cells were markedly cross-sensitive to sodium arsenate and mercury chloride ( LD50 values are one-seventh and one- third LD50 values of wild type ). In addition, the D21 cells showed 1.5-2.0- fold of sensitivity to DNA damage agents ( ENU, cisplatin and r-ray ) and metal compounds ( ZnSO4 and CdCl2 ).