Abstract
The relative deoxyribonucleic acid (DNA) content of cells in culture was determined in a flow microfluorometer after staining with a fluorescent DNA-specific technique. The distribution of the DNA content was used to study the effect of arabinosylcytosine (Ara-C), hydroxyurea, bleomycin and actinomycin D on the progression of the cells through the cell cycle. It was found that short exposures to 10–5 M Ara-C reversibly blocks the cells predominantly in early S phase. The cells blocked in S died after prolonged treatment at low concentrations. A small population was blocked in G1. Similar effects were observed at 10–4 M Ara-C which were irreversible even after short exposures. A block of the majority of the cells in early S and a few cells in G1 was also found with 10–3 M hydroxyurea. Bleomycin resulted in a block in G1 and G2 phases. Actinomycin D treatment at 10–8 M for 24 hr inhibited the initiation of DNA synthesis, since almost all cells were found in G1. The method is very suitable for rapid studies of drug effects on cell cycle progression.