THE EFFECTS OF CYTOSINE ARABINOSIDE ON THE CELL CYCLE OF CULTURED HUMAN LEUCOCYTES: A MICRODENSITOMETRIC AND AUTORADIOGRAPHIC STUDY

PHA-stimulated leucocytes treated with cytosine arabinoside showed a changed uptake of ³H]thymidine, a lowered mitotic index and chromosome damage. Combined autoradiography and Feulgen microdensitometry demonstrated inhibition of DNA synthesis. Cells in the S period of the cell cycle were arrested in their progress, and cells newly entering S accumulated at the beginning of this period. At stronger concentrations these effects on the cell cycle were complicated by the cytotoxic effect of cytosine arabinoside. The inhibition of DNA synthesis is considered in the light of the chromosomal damage and megaloblastic changes caused by cytosine arabinoside, and is compared to the different pattern of DNA arrest found in megaloblastic anaemia.