目的：了解高劑量放射線照射時，維生素丙（ ascorbic acid，AA ）對於中國大頰鼠卵巢（ CHO ）及多形性神經膠質母細胞瘤（ GBM8401 ）細胞輻射生物效應之影響。材料與方法：本研究以體外繼代培養之 CHO 細胞及 GBM8401 細胞為對象，將細胞各分為對照及實驗組，對照組細胞只接受放射線照射（ 8 ～ 16 Gy ），實驗組細胞先以 AA 處理後再接受與對照組相同之放射線照射。照射後的細胞經過十天的培養後以群落分析法計算出其生存分數，並以統計軟體中的線性平方模式（ Linear-Quadratic model ）繪出生存曲線，同時計算其α，β及α / β值。 然後以這些輻射生物反應之參數分析 AA 對於這些細胞的輻射生物效應。結果： 以 8 ～ 16 Gy 高劑量照射 CHO 及 GBM8401 細胞所造成之生存分數（ survivalfraction ）隨著放射劑量之增加而快速遞減。以高劑量照射 CHO 細胞之α / β值為 4.43。 而先以 AA （ 0.025 mg/ml ）處理二小時再接受高劑量照射之 CHO 細胞α / β值為9.28。同樣的，以 8 ～ 16Gy 高劑量照射 GBM8401 細胞α / β值為 9.41。而先以 AA 處理再接受高劑量照射之 BM8401 細胞α / β值為 19.65。 經由 AA 處理後，兩種細胞之生存曲線斜率都降低， 其中以 CHO 細胞較明顯，此種輻射保護效應在 8 ～ 16 Gy 之照射劑量範圍內隨著劑量增加而愈明顯。此外，經 AA 處理後，照射劑量愈高同一細胞之輻射敏感度也降的愈低。兩組細胞之α / β都顯著增加。結論：在高劑量放射線照射下， AA 會降低 CHO 及 GBM8401 細胞的輻射生物效應，且劑量愈高此現象愈明顯。

　　　　　Purpose: Study of the influence of ascorbic acid (AA) on theradiobiologic effects of high dose radiation on CHO and GBM8401 cells.Materials and Methods: CHO and GBM 8401 cells grown in plateau phase were usedin all experiments. Each cell line was further divided into control andexperimental groups, respectively. Cells of control group received irradiation(8 ～ 16 Gy) only. Cells of experimental group were treated with AA and thenirradiated. After 10 days in culture, survival fractions of irradiated cellswere analyzed by clonogenic assay. The survival curves and related parametersincluding α, β, and α / β were analyzed by Linear-Quadratic model.Results: The α / β values of irradiated CHO cells treated with and without AAwere 9.28 and 4.43, respectively. Similarly, The α / β values of irradiatedGBM8401 cells treated with and without AA were 19.65 and 9.41, respectively.Slopes of survival curves for both cells decreased after treatment with AA.However, it was more significant for CHO cells than GBM8401 cells. In addition,the higher the dose of radiation, the greater radio-protective effect of AA oncells.Conclusion: AA decreased the radiobiologic effects of CHO and GBM8401 cellsunder high dose irradiation. The radioprotective effects of AA on these cellswere proportional to radiation dose in the range of 8 ～ 16 Gy.