Life-span investigations for carcinogenicity of some immune-stimulating, immunodepressive and neurotropic substances in Sprague-Dawley-rats.

In a long-term trial in a total of 858 Sprague-Dawley-rats of both sexes the possible carcinogenicity of 12 substances was investigated. Complete Freunds' adjuvant which is among the immune-stimulating substances was found to decrease significantly the lifetime of the animals; whereas an increase in tumor incidences was not observed. Bacille Calmette-Guérin (BCG), human albumin, and vitamin-A-acid were neither carcinogenic, nor had they an influence on the survival times. Rabbit-antirat lymphocytic serum which is a well-known immunodepressive agent caused a significant decrease in survival times, it was not found to be carcinogenic. The known carcinogenic properties of cyclophosphamide were verified. The applied dose of this compound significantly reduced the mean survival times of the animals. Hydrocortisone and amethopterin were found to have no carcinogenic effects. Atropine, pilocarpine, nicotine, and phenyl-ethyl-barbituric acid (phenobarbital) which are known to have neurotropic effects were tested. Nicotine and phenobarbital were found to diminish the mean survival times. None of these neurotropic substances was found to be carcinogenic.