Liver and lung tumors in dogs from 4,4'-methylene-bis(2-methylaniline).

Six female beagle dogs were given, by capsule, a daily dose of 100 mg 4,4'-methylene-bis(2-methylaniline) (MeMDA), 3 times per week for 6 weeks, then 5 times per week for 5 weeks, at which time the dose was reduced to 50 mg 5 times per week, continuously for periods up to 7.0 years. Six female beagle dogs were kept as untreated controls for several studies and were sacrificed after 8.3 to 9 years test. MeMDA dogs developed renal atrophy with an elevated blood urea nitrogen during an approximate six-month period prior to death or being sacrificed in extremis. As three of three MeMDA dogs that survived for 5.2 years to 7.0 years developed hepatocellular carcinomas and two of the three dogs also developed primary lung tumors, with no liver or lung tumor in six control dogs, MeMDA was considered to be carcinogenic for the dog (liver tumors: p less than .05; lung tumors: p less than 10; Fisher's Exact Test, one tail).