Comparison of hepatocyte phenotypes at the glutathione transferase and albumin loci in Sprague-Dawley and Nagase analbuminemic rats and F1 progeny after initiation and promotion

Hepatocarcinogenesis was examined in an initiation-promotionprotocol with a single initiating dose of 7,12-dimethylbenz[a]anthracene(DMBA) followed by promotion with phenobarbital (PB) in theNagase analbuminemic rat (NA), the Sprague-Dawley rat (SD) andtheir F1 crosses. All rats received a 70% partial hepatectomy,followed at 24 h by 30 mg DMBA/kg body wt or the solvent. Aftera 2 week recovery following surgery, half of the solvent controland initiated groups received either basal diet or promotionwith 0.05% PB mixed into the basal NIH-07 diet. After 12 weeksof promotion, the rats were killed and the livers perfused andfixed in situ with paraformaldehyde. Liver slices were paraffinembedded and stained for the placental isozyme of glutathioneS-transferase (PGST). The number of altered hepatic foci (AHF)expressing PGST per liver was determined by quantitative stereologyand used as an endpoint for comparison of initiation in therat strains. The NA rat had a lower response to this initiation–promotionprotocol than did the SD rat. The F1 progeny of the male NAand female SD rats were more similar to the NA parent in theirresponsiveness to initiation, whereas the F1 progeny of thefemale NA and male SD were similar to the SD parent in thisrespect. Putative mutagenesis and carcinogenesis were examinedin the F1 progeny of the female NA and male SD rat. In theserats, serial liver sections were stained either for albuminto detect putative mutations at that locus, or PGST to identifyputatively initiated hepatocytes. In the NA/SD F1, the numberof single hepatocytes with a putative mutation at the albuminlocus was the same (3.710⁵/liver) as those expressing a commonmarker of preneoplasia (PGST). The number of AHF expressingPGST was