Macromolecular synthetic activity in mice regenerating liver after ethylnitrosourea injection

The present report is a continuation of our previous studies on the biochemical mechanisms of carcinogenesis; studying the nature of interactions taking place between Ethylnitrosourea and DNA, RNA and protein of various stages of their synthetic activity. As a model system we chose partially hepatectomized mice live 36 hrs after surgery. Synthetic macromolecule activity in the remaining liver segment was determined by means of 3H-thymidine, 3H-uridine and 3H-leucine. We observed complete depression of DNA synthetic activity (immediately after Ethylnitrosourea administration it remained depressed almost through out the whole period of our observations) while protein synthetic activity was highly elevated. Qualitative changes of soluble proteins which were analyzed by isoelectric fractionation on 5% polyacrylamide after previous 3H- and 14C-leucine incorporation, could not be detected. Our biochemical data are correlated with histological studies and with the tumour incidence following the Ethylnitrosourea treatment of partially hepatectomized mice in the course of long-term experiments. The results provide guideline for further analysis, which should be modified according to the information concerning Ethylnitrosourea carcinogenesis induced 36 hours after partial hepatectmoy.