Carcinogenicity of quinoline, 4- and 8-methylquinoline and benzoquinolines in newborn mice and rats.

The relative tumorigenic activity of quinoline, 4-methylquinoline, 8-methylquinoline, and all three isomeric benzoquinolines was evaluated in newborn CD-1 mice and Sprague-Dawley rats. In the newborn-mouse bioassay, 0.25, 0.5 and 1.0 mumol of each compound in dimethylsulphoxide was administered by ip injection on days 1, 8 and 15 of life, respectively. The bioassay was terminated when the mice were 1 yr old. The incidence of liver tumours observed for those male mice treated with either quinoline or 4-methylquinoline was greater than 78%. 8-Methylquinoline, naphthalene, benzo[f]quinoline, benzo[h]quinoline and phenanthridine did not exhibit significant tumorigenic activity in this bioassay. In contrast to these results, none of these compounds induced a significant incidence of liver tumours in female mice. Each of these aza-arenes was administered to newborn Sprague-Dawley rats by supra-scapular injections of 200 mumol/kg body weight in dimethylsulphoxide on the first day of life, 100 mumol weekly at wk 2-7, and 20 mumol at wk 8. This bioassay was terminated when the rats were 78 wk old. No significant difference in tumour incidence was observed between the pups that had been treated with these aza-arenes and the controls. These data indicate that quinoline and 4-methylquinoline are more potent tumorigens than any of the three isomers of benzoquinoline evaluated in this study. In contrast to the potent hepatocarcinogenic activity observed for both quinoline and 4-methylquinoline in newborn mice, no significant tumorigenic activity was observed with these aza-arenes in newborn rats.