Induction of DNA-repair synthesis (UDS) in rat pleural mesothelial cells by urine of subjects exposed to genotoxic agents.

Unscheduled DNA synthesis was determined in confluent rat pleural mesothelial cells arrested in G0/G1 with hydroxyurea by the measurement of [3H]thymidine incorporation into DNA. Cells were treated with concentrated urine or serum from subjects exposed to certain genotoxic agents, i.e. eight cancer patients treated with radiotherapy and/or chemotherapy (r/c cancer patients) and six chromium workers. Two additional groups consisted of six nonoccupationally exposed healthy smokers and five control volunteers who were nonsmokers and nonexposed. [3H]thymidine incorporated into DNA of all samples was measured by liquid scintillation counting and of urine samples from r/c cancer patients by autoradiography. Compared to the level observed in untreated cells, a statistically significant increased [3H]thymidine incorporation was found in cells treated with urine from 7 of 8 r/c cancer patients and from 5 of 6 chromium workers. In contrast, urine from control volunteers had no effect on the unscheduled DNA synthesis response and urine from only one smoker significantly enhanced [3H]thymidine incorporation into DNA. No clear-cut difference between groups was obtained with serum. These results suggest that urine could be useful to monitor subjects exposed to genotoxic agents.