Mammary tumorigenic effect of a new nitrosourea, 1,3-dibutyl-l-nitrosourea (B-BNU), in female Donryu rats

Four groups (groups 1-4) of female Donryu rats were given continuously 400, 200, 100, or 0 ppm solution of 1,3-dibutyl-1-nitrosourea (B-BNU) as their drinking water, and were studied for the development of tumors. The incidence of mammary tumors was 15/19 (79%), 20/24 (83%), 21/26 (81%), and 8/25 (32%) in groups 1, 2, 3, and 4, respectively. In addition… (More)