[The formation of oval-cell ducts during hepatic carcinogenesis in mice. Its relationship to the pre-existing canals of Hering].

It has been shown that a population of the oval cells is formed in mouse liver during the dipin-induced carcinogenesis (Radaeva, Factor, 1990b). This paper deals with the origin of the oval cells and their proliferation potential depending on localization in the liver lobule. Series of semithin liver sections were studied under the light microscope and detected labeled cells analyzed under electron microscope on serial ultrathin sections. We found that proliferation of cells of terminal bile ductules (Hering [correction of Gering] canals) takes place at the early stages of liver carcinogenesis. These cells and first labeled oval cells had similar size and morphology and jointly formed the ducts. Oval cell population was heterogeneous in terms of proliferative potential. Proportion of proliferating cells (38-45%) in the oval cells of Hering [correction of Gering] canals and small ducts surrounding portal tracts remained similar throughout the period of formation of the oval cell population. In the oval cells infiltrating the parenchyma, the proportion of proliferating cells appeared to depend on the intensity of the oval cell response: it attained the maximum (62%) on intermediate stage and decreased to the minimum (22%) at the peak of the reaction. These data suggest that Hering [correction of Gering] canals probably give origin to the ducts formed by oval cells.