A flow cytometric study of the effect of heat on the kinetics of cell proliferation of Chinese hamster V-79 cells

Abstract. Two methods involving labelling cells with bromodeoxyuridine (BrdUrd) have been used to study by flow cytometry the effect of hyperthermia (43°C for up to 1 h) on Chinese hamster V79 cells. One method involved the use of an antibody to BrdUrd after pulse-labelling the cells either before or at time intervals after treatment. In the second method, the cells were incubated continuously in BrdUrd after heat treatment, and the components of the cell cycle were then visualized by staining with a combination of a bis-bcnzimidazole and ethidium bromide. All three methods showed that heating at 43°C stopped DNA synthesis which, at 37°C, subsequently recovered reaching the normal rate 8–12 h later. The cells in S phase at the time of treatment then progressed to G₂ where they were further delayed. Cells heated in G₁. after the recommencement of synthesis, progressed around the cycle, albeit slower than in unheated cells. The difference between the cells in G₁ and S phases at the time of treatment may account for the greater sensitivity of S phase cells to hyperthermia.