Induction of rat liver gamma-glutamyltranspeptidase-positive foci by oral administration of 1-nitropyrene.

In the present study, the question of whether the ubiquitous environmental pollutant, 1-nitropyrene (1-NP), can induce gamma-glutamyltranspeptidase (GGT)-positive foci, an early lesion occurring during hepatocarcinogenesis, when given orally to F344 rats was examined. Significant induction of GGT-positive foci was observed with all the doses of 1-NP (1000, 500, 250 and 100 mg/kg body wt) used in the present experiment after 6 repeated intragastric (i.g.) intubations when accompanied by partial hepatectomy (PH) performed midway, but not after a single i.g. 1000 mg/kg body wt intubation plus PH. The potential for induction of foci by 1-NP, however, was far less than that by benzo[a]pyrene (B[a]P). The results thus suggested a weak but substantial initiation activity for 1-NP in the rat liver when given orally, particularly with repeated doses.