Tumor induction in mice administered neonatally with 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole or 3-amino-1-methyl-5H-pyrido[4,3-b]indole.

3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) or 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), which is a potent mutagen from pyrolysates of tryptophan, was given subcutaneously to neonatal ICR mice, and all animals were observed for 1 year. Tumors of the livers and lymphoreticular tissue were induced. In the mice given Trp-P-1, the incidences of these tumors were as follows: liver tumors in 45% of the males; malignant lymphoma in 13% of the males and in 24% of the females. In the mice given Trp-P-2, the incidences of liver tumors in the males were dose-dependent (12.5 mg/kg, 12%; 25 mg/kg, 18%), while those of malignant lymphoma varied within a range from 5 to 19%. Statistical analysis revealed that the incidences of the liver tumor in the mice given Trp-P-1 or Trp-P-2 and those of lymphoma in the mice given Trp-P-1 were significantly higher than those of the controls. In the control mice, the incidences of tumors were as follows: malignant lymphoma in 5% of the females; lung tumor in 14% of both sexes.