Liver cancer and precancerous changes in rats induced by the basic fraction of tryptophan pyrolysate.

The basic fraction of a tryptophan pyrolysate (Trp-P-BF) was given orally to Wistar rats for about 2 years. In Experiment I, 5 male rats each were given 0.2, 0.4, 0.6 and 0.8% Trp-P-BF. Dose-dependent growth retardation was observed in these groups and neoplastic nodules were found in the liver of 1 rat given 0.2% Trp-P-BF and a hepatocellular carcinoma was found in 1 rat given 0.4% Trp-P-BF diet. In Experiment II, 25 rats of both sexes were fed 0.5% or 0.2% Trp-P-BF diet. Neoplastic nodules were induced in 2 of 22 males and 5 of 18 females given 0.2% Trp-P-BF diet. Mammary adenomas developed, but no neoplastic nodules were found in the liver of rats fed on 0.05% Trp-P-BF or control diet. Females were more sensitive to Trp-P-BF than males.