Regression of simple hyperplasia and papillomas and persistence of basal cell hyperplasia in the forestomach of F344 rats treated with butylated hydroxyanisole.

The reversibility of forestomach lesions induced in rats by butylated hydroxyanisole (BHA) was examined. F344 rats were given a 2% BHA diet for 24, 48, or 72 wk followed by a basal diet for the remainder of the 96-wk experiment. Two other groups of rats were given a 2% BHA diet or basal diet alone for 96 wk. The forestomach lesions at wk 24, 48, 72, or 96 were compared histopathologically. The results showed that exophytic epithelial proliferation (simple hyperplasia or papilloma) induced by BHA was reversible, while endophytic proliferation of basal cells (basal cell hyperplasia) persisted after withdrawal of BHA administration. This suggests that simple hyperplasia and papilloma of the forestomach induced by BHA are not autonomous and need continuous feeding of BHA to develop further.