DELAY OF CELL CYCLE PROGRESSION AFTER X-IRRADIATION OF SYNCHRONIZED POPULATIONS OF HUMAN CELLS (NHIK 3025) IN CULTURE

Abstract

The effect of X-irradiation on the cell cycle progression of synchronized populations of the human cell line NHIK 3025 [cervical carcinoma] was studied in terms of the radiation-induced delay of DNA replication and cell division. Flow cytometric measurements were made of histograms of cellular DNA content. Parallel use of conventional methods for cell cycle analysis, such as pulse labeling with [3H]thymidine and counting of cell numbers was performed. The 2 sets of methods were generally in good agreement but the advantages of employing 2 independent techniques are pointed out. Irradiation had a minor influence on DNA replication. As compared with unirradiated populations, half-completed DNA replication was 20-30 min delayed in populations given 580 rad in mid-G1 or 290 rad in early S. Cell cycle progression was markedly delayed in G2. The sensitivity induction of this delay was 0.6 min/rad for populations irradiated in mid-G1, and 1.4 min/rad for populations irradiated in early S.