RAPID AND SLOW DNA REJOINING IN NONDIVIDING HUMAN-DIPLOID FIBROBLASTS TREATED WITH BLEOMYCIN AND IONIZING-RADIATION
- 1 January 1985
- journal article
- research article
- Vol. 45 (5) , 1982-1986
Abstract
The rejoining of DNA single-strand breaks produced after bleomycin treatment or .gamma.-irradiation of human diploid fibroblasts was studied by the alkaline elution technique. DNA rejoining occurred at slower rates in bleomycin-treated human fibroblasts than in .gamma.-irradiated fibroblasts. These comparisons were made at similar levels of similar or DNA single-strand breaks (including alkali-labile lesions). Significant numbers of DNA single-strand breaks were detected routinely after two 8 mg/ml (1.34 .times. 10-6 M) bleomycin treatments (for 30 min, survival > 70%). Dose-dependent losses of .apprx. 3-15% of total radioactivity were measured in preelution samples from cells treated with bleomycin (2 to 100 .mu.g/ml), but only 2-3.5% of total radioactivity was assayed in lysis samples from cells irradiated with 200-1000 rads. DNA thus was more degraded by or after bleomycin treatment. DNA was rejoined extremely rapidly after bleomycin or radiation treatments and the rejoining was both agent- and dose-dependent. Over dose ranges yielding surviving fractions of 75-0.056%, considerable DNA rejoining occurred after only 2.5 min posttreatment incubation in conditioned medium. Cellular recovery occurred at faster rates after bleomycin treatments than after .gamma.-irradiation, while DNA rejoining occurred at faster rates after .gamma.-irradiation, thus uncoupling DNA repair and cellular recovery in relating the cellular action of these 2 agents. No consistent differences were observed among 3 normal fibroblast strains and fibroblasts from a Gardner''s syndrome patient (deficient in their capacity for cellular recovery) or a Turcot''s syndrome patient in the formation and rejoining of single-strand breaks after bleomycin or radiation treatments.This publication has 12 references indexed in Scilit:
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