[Effect of partial hepatectomy on the state of liver chromatin in adult and old rats].

Partial hepatectomy in rats of two age groups--adult (6-8 months) and old (24-26 months)--is found to increase the intensity of [2-14C] orotic acid incorporation into RNA of the liver chromatin which reaches the maximum values 15 h after the operation simultaneously in animals of both groups. In the age groups under study the transcription activation is accompanied by an increase in the relative quantity of the active chromatin fraction. The study of the process of thermodenaturation of inactive and active chromatin fractions in the liver of adult rats after the partial hepatectomy has revealed no considerable shifts in the melting point and in distribution of the hyperchromism percentage within different temperature ranges as compared to the intact liver. Parameters characterizing the melting process of chromatin fractions in the regenerating liver of old animals differ from the analysis of the intact liver: the melting point decreases and hyperchromism percentage distribution varies. The chromatin activation with the liver regeneration leads to more pronounced changes of its properties in old animals as a result of which age differences observed in the intact liver are levelled.