Tumors of the heart and stomach induced in European hamsters by intravenous administration of N-methyl-N-nitrosourea.

One hundred twenty captured European hamsters (Cricetus cricetus L.) were inoculated iv with 1/5, 1/10, or 1/20 the median lethal dose of N-methyl-N-nitrosourea (MNU) once weekly for 18 weeks. MNU induced mainly sarcomas in the heart and squamous cell carcinomas and sarcomas in the stomach. The highest incidence of such tumors was demonstrated by the lowest-dosage group. They were more frequent in males than in females. The effect of MNU was also localized at the site of administration and resulted in squamous cell carcinomas of the oral cavity. The possible fibroblastic or neurogenic origin of the sarcomas was explored.