Radiation-induced synchronization of the Walker carcinoma in vivo

Abstract Exponentially growing Walker tumours of a weight of 1·0 ± 0·3 g were irradiated at a 200 kV p X-ray unit with single and fractionated doses ranging from 50 to 900 rads. The influence of the radiation on the cell cycle of the carcinoma was studied using a pulse-cytophotometer. By this method DNA distribution patterns of the tumour cells are obtained. The mathematical analysis of these DNA distributions using a computer program gives the percentage of cells belonging to the various phases of the cell cycle. The results show a reversible accumulation of cells in the G 2 -phase and a partly synchronous passage of cells from G 2 -phase into mitosis and G 1 -phase. With the highest dose applied, the fraction of cells in G 2 could be increased from 14 to 48% . The degree of synchrony obtained is compared with the values determined after chemical treatment in vivo .