Studies on the induction of chromosomal aberrations in human leukocytes by cytosine arabinoside

Studies were performed on the action of the nucleic acid base analogue, cytosine arabinoside, on human leukocyte chromosomes. It was found that cytosine arabinoside could induce chromosomal aberrations at all times during the cell cycle. It was found, however, that the chemical had very little, or no, effect on the chromosomes of unstimulated leukocytes. Addition of deoxycytidine during, but not after, the treatment with cytosine arabinoside resulted in a decrease in the yield of aberrations indicating it was affecting the induction of the aberrations. These results are interpreted to mean that cytosine arabinoside does not induce aberrations by inhibiting the replication of chromosomal DNA. The induction of the aberrations is believed to be closely related to nucleoside pool formation and nuclease activity in the cell, possibly in a way proposed by Ahnström and Natarajan [1].