title: Effect of caffeine on gamma-ray-induced G2 delay in ataxia telangiectasia.
abstract: Exposure of normal control and ataxia-telangiectasia (A-T) lymphoblastoid cell lines to ionizing radiation gives rise to an increase in the proportion of G2 phase cells. The size and extent of the G2 phase block is greater in A-T cells than in normal cells. Caffeine has a similar overall effect in control and A-T cell lines in reducing the G2 arrest observed after ionizing radiation. While the proportion of cells accumulated in G2 in A-T cells is considerably greater than in controls, addition of caffeine at the time of maximal G2 block brings about a return of G2 phase cell numbers to unirradiated values in 3 hours in both cell types. In normal control cells the caffeine-mediated decrease in G2 cells is reflected by an increase in mitotic cells. These mitotic cells have a higher frequency of chromosome aberrations compared to cells harvested in the absence of caffeine. Similarly in A-T cells addition of caffeine to irradiated cultures, delayed in G2 phase, increased the number of mitotic cells and the frequency of chromosome aberrations.
mesh_terms: D001260:Ataxia Telangiectasia / Q000473:pathology*; D002110:Caffeine / Q000494:pharmacology*; D002460:Cell Line; D002869:Chromosome Aberrations; D003037:Cobalt Radioisotopes; D004247:DNA / Q000528:radiation effects*; D005434:Flow Cytometry; D005720:Gamma Rays; D006801:Humans; D066298:In Vitro Techniques; D007399:Interphase / Q000187:drug effects / Q000528:radiation effects*; D008214:Lymphocytes / Q000528:radiation effects; D013997:Time Factors
chemical_list: D003037:Cobalt Radioisotopes; D002110:Caffeine; D004247:DNA