It is hypothesized that the liver has 3 levels of cells in the hepatic lineage that respond to
injury or carcinogenesis: 1) the mature hepatocyte, which responds to partial hepatectomy
(PH), to centrolobular injury, such as that induced by carbon tetrachloride (CCl4), and to
dimethylnitrosamine (DEN) hepatocarcinogenesis; 2) the ductular “bipolar” progenitor cell,
which responds to centrolobular injury when the proliferation of hepatocytes is inhibited, and
to N-2-acetylaminofluorene (AAF) hepatocarcinogenesis; and 3) the putative periductular …