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Effects of Oxygen Concentration on Carcinogenesis Induced by Transplacental Exposure to Urethan

( Roswell Park Memorial Institute, New York State Department of Health, Buffalo, New York)

The incidence of lung tumors was studied in hyperoxic and hypoxic pregnant A mice given injections intravenously of 25 mg. of urethan, and in their offspring. Among progeny born within 24 hours after their mothers received urethan, those born in an environment of approximately 100 per cent or 10 per cent O₂ developed a significantly greater number of pulmonary tumors than did controls born in room air. The average number of tumors decreased significantly in all progeny from mothers given injections earlier than 24 hours prepartum. Myeloid leukemia and extramedullary hematopoiesis were also induced or potentiated by urethan. Mothers in all groups had more pulmonary tumors than their offspring had; 48-hour exposure resulted in an increased average number for mothers kept hyperoxic, as compared with those kept hypoxic or in room air. Mothers in all three groups developed a high incidence of mammary carcinomas.

Received 9/25/61.