Sequential analysis of quinoline-induced hepatic hemangioendothelioma development in rats.

The effect of duration of quinoline treatment on the induction of hepatic hemangioendotheliomas was examined. Groups of male Wistar rats were given 0.25% quinoline in the diet for 4, 8, 12, 16 or 20 weeks and sequentially killed at these time points. Hemangioendotheliomas were only induced in the livers of rats given quinoline for more than 12 weeks and the incidences of small foci of dysplastic endothelial cells and tumors at week 20 did not differ between the 12-, 16- and 20-week-treated groups. Quantitative analysis of the liver sections at week 20 revealed increased relative area occupied by sinusoidal space even after only 4-week exposures. Parenchymal hyperplastic nodules were observed only in one rat each of the 16- and 20-week-treated groups. The present study indicates that dysplastic endothelial foci may develop into hemangioendotheliomas irrespective of whether the carcinogenic stimulus is continued.