Growth and polyploidization of the liver of early postnatal rats treated with bleomycin

Bleomycin was administered to 6- and 10-day-old rats and its effects were examined after a two-week survival period. Decreases in body weight and some phenotype abnormalities occurred in both age groups. Decreased relative liver weight (g/g b.w.) was observed only in animals injected on PD 10. DNA microdensitometry and microfluorometry (Feulgen reaction and Hoechst 33342 staining) revealed an increase in the frequency of intermediate DNA values in animals injected on PD6 and killed on PD20. In older animals, i.e. in rats injected on PD10 and killed on PD25, increases in 4c mononucleate and 8c binucleate cells and also a reduction of the relative number of binucleate cells appeared, as compared with age-matched controls. In both age groups, karyological abnormalities, including micronucleate cells and imbalanced DNA content in binucleate cells, were observed.