The effect of added dietary tryptophane on the occurrence of 2-acetylaminofluorene-induced liver and bladder cancer in rats.

Recent reports by Bielschowsky (1), Harris (6), Engel and Copeland (5), Strombeck and Ekman (10), and Morris et al. (7), indicate that the genetic constitution of the rat plays a more dominant role than diet in the initiation of 2-acetylaminofluorene-induced neoplasms. While liver tumors occur in a majority of the rats and the frequency is altered somewhat by the protein content of the diet, the mechanism of tumor formation differs from that of dimethylaminoazobenzene carcinogenesis, in that liver extract and riboflavin exert no protective effect against the action of this drug. 2-Acetylaininofluorene-induced mammary gland and bladder neoplasms appear to be peculiarly strain limited. In a preliminary survey of five strains of rats, Dunning, Curtis, and Madsen (2) showed that 2-acetylaminofluorene-induced bladder tumors were confined to the Copenhagen and AXC strains and that tumors of the mammary gland were relatively infrequent, with only two ob served in rats of the Fischer strain and one each in rats of the August and AXC strains. Tumors of the liver occurred in rats of all five strains but were less frequent in rats of the Copenhagen strain. A later study (4) of the occurrence of diethylstilbestrol-induced tumors in rats of three of these strains showed that mammary tumors were most frequent in the AXC rats, occurred with low fre quency in Fischer rats, and failed to occur in rats of the Copenhagen strain, while the induced blad der cancers were most frequent in the Copenhagen rats, occurred with low frequency in rats of the AXC strain, and failed to occur in Fischer rats. Rats of the Fischer strain were chosen for the present study because of their relatively high inci dence of liver tumors and a low incidence of mammary tumors which might serve as compara-