O-Aminoazotoluene as a Carcinogenic Agent *

In 1932, 1933, and 1934 Yoshida5' 6, 7,8,9 announced the production of liver-cell tumors in the white rat after prolonged feeding with o-aminoazotoluene (2-amino-5-azotoluene). This compound is dosely related to the azo dye, Scharlach R, and is structurally unlike any of the carcinogenic hydrocarbons of the phenanthrene series. Aside from structure, the compound has aroused considerable interest through its apparently selective action upon the liver. Wolbach4 studied this and found necrosis followed by regeneration of the liver cells. In 1937, Shear3 announced the production of multiple tumors of the liver in pure-strain mice receiving the solid dye subcutaneously. At the same time he reviewed the literature of experimental work with the azo compounds, including the most recent results of Yoshida and his associates. In 1937 also, Heep1 fed o-aminoazotoluene to a number of rats previously treated with small doses of arsenic. These rats did not develop tumors. In another series, not given arsenic, but fed on unpolished rice after the manner of Yoshida, marked regenerative phenomena were described in the liver. As the animals in the arsenic series had been fed differently, Heep was unable to rule out a possible dietary factor in the explanation of the results. The purpose of the present experiment, begun in 1935, was the confirmation of Yoshida's original work. This was repeated with certain technical modifications, induding a balanced diet.