The effect of G2-treatments with 2'-deoxyadenosine on the frequency of chromatid aberrations in human lymphocytes depends on the type of culture.

The effect of G2-treatments with 2'-deoxyadenosine (dAdo) on the frequency of chromatid aberrations in X-irradiated and unirradiated human lymphocytes depends on the method of culture. In whole-blood cultures dAdo alone produced very few if any aberrations, but in the presence of inhibitors of adenosine deaminase (ADA), such as EHNA or coformycin, a high frequency of chromatid gaps, chromatid breaks, and isochromatid breaks were produced. In cultures of purified lymphocytes, dAdo produced aberrations even in the absence of an ADA inhibitor. Apparently the lymphocytes are protected against the chromosome-damaging effect of dAdo by the ADA activity of the erythrocytes. --When given as a post-treatment, dAdo also enhances the frequency of chromatid aberrations induced by X-rays in G2. In whole-blood cultures this effect is obtained even in the absence of an ADA inhibitor, although the concentration required to produce enhancement is about twenty times higher than in the presence of the inhibitor.