INDUCTION OF ANGIOGENIC TUMORS IN THE DUODENUM OF FEMALE DONRYU RATS BY CONTINUOUS ORAL ADMINISTRATION OF N-ISOBUTYL-N-NITROSOUREA

Four groups of female Donryu rats were continuously given 400, 200, 100 or 0ppm N-isobutyl-N-nitrosourea (iso-BNU) in their drinking water, and were examined for the development of tumors. The incidence of digestive tract tumors was 25/28 (89%), 14/24 (58%), 6/25 (24%) and 0/17 (0%), in the 400, 200, 100 and 0ppm groups, respectively. The predominant type of digestive tract tumor wasangiogenic, and a few were of the epithelial type. A dose-effect relationship was clearly demonstrated not only in the incidence of digestive tract tumors but also in the average survival period of rats with these tumors.