[Liver growth fraction, its composition with regard to cell ploidy and changes with aging]

All the hepatocytes incorporating 3H-thymidine under the continuous labeling during the liver regeneration were classed with the fraction of liver growth (proliferative pool). The continuous labeling of proliferating cells was ensured by the injection of a high dose of 3H-thymidine prior to the operation. It was shown that after partial hepatectomy in young mice the label is incorporated by practically all parenchyma whereas in old ones its significant part does not proliferate. Highly ploid cell types predominated among hepatocytes which lost their ability of reproduction.