Antiteratogenic and anticarcinogenic effects of X-rays in urethane-treated NMRI mice.

A single intraperitoneal injection of urethane (ethyl carbamate) induces lung tumours in 80 per cent of male and 100 per cent of female NMRI mice, respectively. In the course of time the initially benign adenomatous tumours can develop into malignant adenomatosis of the lung (alveolar cell carcinoma). For an analysis of the mechanisms of tumour development and the possible interactions involved, low doses of X-rays (5-100 cGy) were administered 6 hours after urethane treatment. A significant anticarcinogenic and, also, anti-teratogenic action was observed. This implies that in both cases similar mechanisms are involved. Single injections of vitamin C or chloroquine counteract the urethane effects in the same manner as do the low doses of X-rays, but probably by different mechanisms.