Dose‐dependent Induction of Liver and Thyroid Neoplastic Lesions by Short‐term Administration of 2‐Amino‐3‐methylimidazo[4,5‐f]quinoline Combined with Partial Hepatectomy Followed by Phenobarbital or Low Dose 3′‐Methyl‐4‐dimethylaminoazobenzene Promotion

Dietary administration of 0.1, 0.05, or 0.025% 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ) for two weeks combined with partial hepatectomy at the end of the first week and followed by long‐term treatment with phenobarbital (PB) or 3′‐methyl‐4‐dimethylaminoazobenzene (3′‐MeDAB) from week 3 to week 86 resulted in dose‐dependent development of liver and thyroid neoplastic and preneoplastic lesions. Quantitation of glutathione S‐transferase placental form (GST‐P)‐positive hepatocellular focal populations revealed a significant correlation of IQ concentration with lesion area, with a yield approximately equal to that generated by a similar dose of 2‐acetylaminofluorene. The fact that IQ was less toxic therefore allowed greater yields of hepatocellular carcinomas to be induced. The development of thyroid tumors initiated by the IQ treatment was significantly enhanced by the administration of PB, whereas Zymbal gland tumors induced by IQ did not show any correlation with either PB or 3′‐Me‐DAB treatment.