title: Adaptive response of human lymphocytes to low concentrations of radioactive thymidine.
abstract: When human lymphocytes were cultured with [3H]thymidine, which acts as a source of low-level chronic radiation, and then exposed to 150 rad of x-rays at 5, 7, 9, or 11 hours before fixation, the yield of chromatid aberrations was less than the sum of the yields of aberrations induced by [3H]thymidine and x-rays separately. Often fewer aberrations were found after exposure to radiation from both sources than were found after exposure to x-rays alone. At the same fixation times, nonradioactive thymidine did not affect the yield of x-ray-induced aberrations. The same phenomenon occurred at earlier fixation times, after exposure to 30 or 40 rad of x-rays and [3H]thymidine. This response is analogous to the adaptive response to alkylating agents whereby prior treatment with small doses for a long period reduces the damage occurring from large doses of similar agents given for a short time.
mesh_terms: D002478:Cells, Cultured; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D008677:Metaphase / Q000187:drug effects / Q000528:radiation effects; D013936:Thymidine / Q000633:toxicity*; D014316:Tritium
chemical_list: D014316:Tritium; D013936:Thymidine