6-p-Dimethylaminophenylazobenzothiazole: a potent hepatocarcinogen in the rat.

6-p-Dimethylaminophenylazobenzothiazole (6BT) administered at a dose of 10 mg/kg by gavage to Sprague-Dawley and Wistar-derived rats for 2 months produced marked cellular changes in the liver, including proliferation of oval cells and the formation of regenerative/hyperplastic nodules. Cellular change continued after stopping dosing at 2 months such that liver tumours were first observed after only 4 months into the study, and animals examined between 4 months and termination at 6 months showed a 75% and 85% incidence of hepatocellular carcinoma for the Sprague-Dawley and Wistar strains, respectively. This study establishes 6BT as a potent hepatocarcinogen in the rat when administered by gavage, and confirms and extends an initial brief report by Brown and Sanchorawala in 1968 of its carcinogenicity following dietary administration.