根據先前的研究結果，若中國蒼鼠卵巢細胞（CHO-K1）經過短波長紫外線（UVC）照射之後再接觸秋水仙胺（colcemid），相較於僅照射紫外線的細胞，前者的存活率會大為下降。而在本研究中，利用四唑鹽分析方法（MTT assay）發現，秋水仙胺加重紫外線所誘發細胞死亡的效果在核酸切除修復機制缺陷（NER-deficient）的中國蒼鼠卵巢細胞（UV24）中並不顯著，暗示其作用可能是藉由影響核酸切除修復機制而得以發揮。在進一步的研究中，利用酵素連結免疫吸附法（ELISA）定量短波長紫外線所產生的去氧核糖核酸傷害時，發現秋水仙胺並不會抑制傷害的移除，但是根據彗星檢測法（comet assay）的結果，此藥物卻會增加紫外線所導致之去氧核糖核酸斷裂程度。由於秋水仙胺並不會抑制非計畫性去氧核糖核酸的合成，因此推測核酸斷裂程度的增加是由於核酸切除修復機制中核酸連結步驟（ligation）受到抑制。此結果也暗示秋水仙胺可能是藉由抑制此連結步驟而加重紫外線所誘發之細胞死亡。

Previous studies have indicated that the survival of Chinese hamster ovary cells (CHO-K1) after ultraviolet C irradiation (25 J/m2) is greatly reduced if cells are treated with colcemid (50 ng/ml) after irradiation. This inhibitory effect of colcemid was also detected in my study with EM9 cells but not with UV24 cells. EM9 and UV24 cells are both the derivatives of CHO cells except that EM9 and UV24 cells have defect in base-excision repair (BER) and nucleotide excision repair (NER), respectively. This observation suggests that the colcemid’s effect was NER dependent. Further study with enzyme-linked immunosorbent assay using specific antibodies to two major UVC-induced DNA damages, i.e. cyclobutane pyrimidine dimer (CPD) and 6-4 photoproduct (6-4 PP) shows that colcemid did not affect the excision of CPD or 6-4PP. However, study with the comet assay indicates that colcemid increased the DNA breaks in UVC-irradiated cells. Further analysis reveals that colcemid did not inhibit the unscheduled DNA synthesis. Taking together, I hypothesize that colcemid might inhibit the step of ligation of NER pathway.

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