ABSTRACT
To study the effects of fractioned ir radiation on the total RNA and MDR 1 mRNA of NCI H 446 small cell lung cancer cell line, NCI H446 cells in the period of exponential growth were exposed to 60 Co ? radiation at 2 Gy/fraction, 2 fraction/week, with the cumulative dose of 50 Gy by 25 fractions. The total RNA of the cells of the irradiated group and control group were extracted by the acid guanidine thiocyanate phenol chloroform method and the amount of the expression of MDR 1 mRNA was assessed by qualitative RT PCR assays. Under the conditions of same cell number and volume, in cells of the control group, the concentration of the total RNA was 25 9 ?g/ml and the ratio of MDR 1 DNA/? actinDNA was 1 078, whereas in cells of the irradiation group, the corresponding values were 16 6 ?g/ml and 1 338, respectively. It is concluded that, for the NCI H446 small cell lung cancer cell line, a high dose accumulated during fractioned irradiation can inhibit the synthesis of its total RNA and enhance the expression of its MDR 1 gene at the same time.