Comparative carcinogenesis by some aliphatic nitrosamines in Fischer rats

The carcinogenic effectiveness of 5 simple aliphatic nitrosamines was compared by feeding to groups of 20 Fischer rats in drinking water. Nitrosodi-isobutylamine was by far the weakest carcinogen, giving rise after comparatively high doses to tumors of the nasal cavity and trachea. Nitrosodimethylamine (NDMA) induced almost exclusively hemangiosarcomas of the liver, whereas nitrosodiethylamine (NDEA) gave rise to a high incidence of hepatocellular carcinomas, after administration of approximately the equivalent dose; all of the animals also developed tumors of the esophagus. Nitrosomethylethylamine (NMEA) induced both hemangiosarcomas and hepatocellular carcinomas, together with some esophageal tumors, but must be considered a weaker carcinogen than the dimethyl or diethyl analogs, since a much higher dose was needed to achieve a comparable effect. Nitrosodi-n-propylamine (NDPA) was of comparable potency with NDMA and NDEA, but gave rise under these conditions only to tumors of the esophagus and forestomach, and induced no liver tumors.