Kinetics of chromosomal aberrations and first mitosis division in human lymphocytes exposed to mitomycin C

In order to understand the relationship between the chromosomal damage detectable at the first mitosis after mutagen treatment and the induced mitotic delay we studied the time pattern of both mitotic indices and chromosomal aberration frequencies in human lymphocytes treated in G1 with mitomycin C (2.5 microM) and cultured in vitro in the presence of 5-bromo-2'-deoxyuridine. Mitotic delay was observed in treated cells cultured for 81 h. At this point an increase in the frequency of chromosomal aberrations is evident and a higher proportion of abnormal cells enters mitosis, the long delay being due to the extensiveness of DNA damage. The importance of cell cycle progression for the detection of the maximal amount of induced chromosomal damage is discussed.