9-beta-D-arabinofuranosyladenine increases the frequency of X-ray induced chromosome abnormalities in mammalian cells.

Treatment of X-irradiated stationary Ehrlich ascites tumour cells with the DNA synthesis inhibitor beta-ara A (120 mumol/l, 30 min before and for 7 hours after irradiation) is shown to lead to a large increase in the incidence of anaphase chromosome abnormalities (anaphase bridges and fragments) at the first mitosis following irradiation. This increase is similar to the increase in cell killing observed for this cell line when treated with beta-ara A under the same conditions (Iliakis 1980). The results suggest that the increased frequency of chromosome abnormalities caused by beta-ara A may result not only from the inhibition of DNA double strand break repair, leading to additional unrepaired d.s.b. (Bryant and Blöcher 1982) and chromosome deletions, but also from an increase in the frequency of misrepair of d.s.b. leading to exchange aberrations.