"Lifespan" of Liver Cells

Little information is available concerning the lifespan of liver cells in the normal and diseased liver. This is a study of the length of time that newly formed hepatic nuclei containing tritium (H3)-labeled deoxyribonucleic acid (DNA) remain in the liver in normal rats and mice, and in rats with fatty, cirrhotic, and partially hepatectomized liver. The method was as follows. It has been observed that thymidine is a specific precursor of DNA,1which is considered to be relatively stable until a cell prepares for division, at which time the cell synthesizes additional DNA.2The half-life of tritium is 12.5 years,3and that of the rat is approximately 3 years,4so that tritiated thymidine (H3-thymidine) incorporated into cell nuclei should identify those nuclei for the life of the animal, until the cells divide further, diluting out their labeled DNA, or until the cells