Cell-stage-specific enhancement by caffeine of the frequency of chromatid aberrations induced by X-rays in neural ganglia of Drosophila melanogaster

Caffeine (10(-2) M) induced a high level of chromatid aberrations in neural ganglia of third-instar larvae of Drosophila melanogaster only when it was added to cells in late G2 and mitotic prophase. No aberrations were observed after treatment in late S--middle G2 or C-mitosis. We observed that, in these stages, caffeine strongly increased X-ray-induced damage (500 R). This potentiation was quantitatively similar. But it involved all types of aberration after treatment in C-mitosis, and essentially isochromatid deletions and chromatid exchanges after treatment in S--G2. Some hypotheses are put forth to explain the possible mechanism of action of caffeine in the potentiation of X-ray-induced damage.