[Analysis of the DNA content of urethane-induced liver tumors in mice]

Administration of urethan (three times per 1 mg calculated per 1 g of the animal mass) after partial hepatectomy resulted in the development of liver tumours classified as adenomas in 62.8 per cent of mice 12 months after treatment. In the cells isolated from 85 adenomas and from the surrounding liver, DNA-fuchsin content was determined cytophotometrically. Three types of DNA distribution were distinguished, with the mode in the region of near-diploid (26%), near-tetraploid (71.8%), or near-octaploid (2.2%) DNA value. Most commonly DNA distributions were polymodal, but unimodal ones also occurred. The number of binucleated cells in tumours was significantly decreased. In the liver of one of the same animal, morphologically similar tumours of all the three types of DNA distribution could be found. The increase in the hepatocyte ploidy level in the initial parenchyma by preliminary repeated treatments with CCl4, had no effect either on the occurrence of tumours, or on their ploidy level. No correlation was found between the DNA content, the size and histological structure of tumours.