[Cellular mechanisms of cirrhotic rat liver regeneration. II. Proliferation, polyploidization and hypertrophy after partial hepatectomy].

Using cytofluorimetry and absorptional cytophotometry, hepatocyte DNA and total protein contents were measured in intact and cirrhotic rats in 1, 3 and 6 months after partial hepatectomy (PH). It has been found that within one month of intact rat liver regeneration the level of hepatocyte ploidy rised by 25% to remain elevated for the next 6 months. This was due mainly to reducing the number of cells with diploid nuclei (2c 2-fold, 2c x 2 - 6.6-fold) and to rising the number of octaploid hepatocytes. In cirrhotic animals the ploidy level in hepatocytes increased in 3 months after PH, and decreased by 15% in 6 months. The number of hepatocytes with diploid nuclei (2c and 2c x 2) increased within 3-6 months in both control and cirrhotic rats. The protein content per diploid hepatocyte rised by 30% within 3-6 months of liver regeneration after PH. Special calculations have shown that within 3 months after PH the increase in the liver mass of control and cirrhotic rats was due completely to hepatocyte DNA synthesis, i. e. proliferation and polyploidization. Within the next 3 months of liver regeneration after PH, the contribution of polyploidization to liver mass increase was negative because of depolyploidization of liver parenchyma cell population. At this time hypertrophy was the main process determining the liver mass increase.