Carcinogenicity of nitrosotrialkylureas in Fischer 344 rats.

Three nitrosotrialkylureas were administered to female F344 rats as approximately 1-mM solutions in drinking water. Nitrosotrimethylurea, given for 47 weeks, gave rise to astrocytomas of the brain and tumors of the forestomach; nitrosotriethylurea induced a high incidence of adenocarcinomas of the breast and uterus and tumors of the forestomach. Nitrosomethyldiethylurea induced almost exclusively a high incidence of both astrocytomas of the brain and tumors of the spinal cord.