Effect of timing of partial hepatectomy on the induction of preneoplastic liver foci in rats given hepatocarcinogens.

Beginning 2 weeks after an intraperitoneal injection of diethylnitrosamine (DEN), rats were fed diet containing either 2-acetylaminofluorene (2-AAF), 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB), alpha-isomer of 1,2,3,4,5,6-hexachlorocyclohexane (alpha-HCH), or phenobarbital (PB) for 6 weeks and subjected to partial hepatectomy (PH) after various periods of chemical administration. The effect of timing of PH was most apparent in rats fed 2-AAF. The size of gamma-glutamyl transpeptidase positive foci was largest when PH was performed 1-3 weeks after the start of chemical feeding. Similar tendency was slightly observed with 3'-Me-DAB or alpha-HCH administration, but not with PB or basal diet feeding. Thus, the enhancing effect of PH on the induction of the preneoplastic liver foci was affected by the type of chemical and the timing of the operation.