Urethane-induced lung adenomas in the first-generation progeny of irradiated male mice

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Abstract
A carcinogenic effect of urethane on the first-generation progeny of irradiated male mice was investigated. Seventy SHR male mice were exposed to a single total-body X-ray irradiation at a dose of 4.2 Gy. Each of these animals was then caged with three intact females for 7 days. Thirty non-irradiated males were handled in the same way. Three-month-old offspring of irradiated (F1i) and control (F1c) males were treated with urethane at a total dose of 50 mg/animal (0.1 ml of 10% urethane water solution was injected five times at 3-day intervals). Three months after the first injection animals were killed and the lung adenomas found were studied. A group of animals kept until natural death revealed leukemia and mammary tumors. The frequency of lung-tumor-bearing animals was equal in both F1i and F1C groups. However, 12.9% of F1i mice had >11adenomas per animal (average 17.6 ± 1.36 tumor nodes/mouse; maximum 35 nodes). The portion of such animals in the F1C was only 6.6% (average 14.0 ± 0.77 nodes/mouse; maximum 18 nodes). The size of tumors did not differ significantly in the two groups. The incidence and latency of leukemia were similar in both groups, though the first case was registered earlier in F1i. A tendency to a higher frequency and earlier development of mammary adenocarcinomas was noted in the experimental group. The data obtained evidence the increased cancer risk in the progeny of irradiated male mice to be one of the genetic consequences of ionizing radiation.