LACK OF CARCINOGENICITY OF CYANOGUANIDINE IN F344 RATS

The carcinogenicity of cyanoguanidine, a compound used in the producti on of melamine, guanidine salts and guanamine derivatives, was examine d in male and female Fischer 344 rats fed CRF-1 pulverized diets conta ining 0, 2.5 and 5% cyanoguanidine for up to 2 yr. The rats were rando mly allocated to three groups, each consisting of 50 males and 50 fema les. The mean body weight gains in both sexes of the 5% group and in f emales of the 2.5% group were significantly lower than the control val ues after wk 1 of treatment. No other signs of toxicity were seen in a ny of the rats throughout the treatment period. Histopathologically, v arious tumours developed in all groups, including the control group, b ut these were all similar to those known to occur spontaneously in thi s strain of rats, and no toxicologically significant increase was foun d for any lesion type in the treated groups. On the basis of these res ults, it is concluded that cyanoguanidine exerts no carcinogenic poten tial in F344 rats when administered for up to 2 yr under the condition s of the present study. (C) 1997 Elsevier Science Ltd.