Nuclear Alterations During Hepatocarcinogenesis: Promotion by 2-Acetylaminofluorene

Abstract

Normal liver growth takes place partly by ordinary cell division, partly by polyploidization. The latter mechanism becomes increasingly dominant as the animal matures and ages. In adult rats of the Wistar Kyoto strain, the majority of the hepatocytes (60%) are tetraploid, 20–25% are octoploid, and about 15% are diploid. The latter, being of small size, make up less than 10% of the liver mass. Fig. 1A shows the increase in absolute hepatocyte numbers, and Fig. 1B the contribution of the various cell ploidy classes to liver weight following a 2/3 partial hepatectomy in the young (70–100 g) animal. There is a rapid increase in all mononucleated cell types during the regeneration phase (the first week); subsequent liver growth is dominated by polyploidization and tetraploid cell division, and there is actually a decrease in the number of diploid cells.