AGING AND RADIATION-INDUCED ALTERATIONS OF HISTONES IN REGENERATING RAT-LIVER

We studied the age-related and radiation-induced changes in histones i n regenerating liver of rats between 1 and 28 months of age. The exami nations were carried out 30 h after a two-third hepatectomy, i.e. afte r the first wave of DNA and histone synthesis. During induced regenera tion age-related changes in liver manifested themselves in decreasing the cellularity per gram wet weight, in slowing down the increase in D NA and histone contents per organ, in changing the mutual proportions of histone fractions H1, H2A + H2B, H4 and in increasing the H1-degree s variant within histone H1. Radiation-induced latent injury (a dose o f 5.7 Gy gamma radiation 30 min before partial hepatectomy) was manife sted during induced regeneration in similar but much more profound cha nges with their earlier onset. Since the changes in regenerating liver were found not to be milder than in intact liver it means, that induc ed proliferation did not lead to elimination of altered cells or to th eir rejuvenation.