紫外線在吳郭魚細胞之DNA複製及修補上的影響

Abstract

本實驗是利用已建立的吳郭魚腎臟細胞株（Tilapia kidney cell line; TK）為實驗材料，研究紫外線（Ultraviolet light; UV）對其細胞遺傳物質一一DNA所造成的損傷（damage）及其修補（repair）情形，並以中國倉鼠卵巢細胞株（Chinese hamster ovary cell line; CHO）與之對照. TK細胞經過UV照射後，在不同的時間以放射性物質（3H-Thymidine and/or 14C-Thymidine）標誌DNA，結果顯示TK細胞具有較其他魚類細胞及哺乳類細胞為高的UV忍受力，而且在DNA合成速率下降及復原的反應程度上也較哺乳類細胞明顯。由中性蔗糖梯度溶液離心分析與鹼性蔗糖梯度溶液離心分析的實驗結果顯示，TK細胞具有顯著的切除修補機制（Excision repair)及複製後修補機制（Postreplication repair）。目前為止一般研究者認為，在魚類細胞中並不具有切除修補機制，本實驗為第一個證實魚類細胞（吳郭魚）具有切除修補能力。 另一個實驗結果顯示，TK細胞對於DNA合成抑制劑,如Hydroxyurea (HU)、1-β-D-arabinofuronosyl cytosine(araC)的敏感度較CHO及其它哺乳類細胞低，然而這種差異性卻無法由細胞內DNA合成先驅物（DNA synthesis precursors）含量差異而予以解釋。

The effect of ultraviolet radiation on cell line established from warm water fish Tilapia has been assessed by rate of DNA synthesis, excision repair, post-replication repair and cell survival, The cells tolerate UV better than mammalian cells with respect to DNA synthesis, posreplication repair and cell survival. It is also efficient in excision repair wich in other fish cell lines has been: found to he low or none. The response to inhibitors hydroyurea (HU) and 1-β-D-arabino-furano-sylcytosine (araC) is less sensitive than that in other cell lines, yet the cells seem to have very small DNA precursor pool. Possible explanation is that Tilapia cells have a very fast turnover rate of DNA precursors.