AGING AND RADIATION-INDUCED ALTERATIONS IN LIVER HISTONES

Age-related changes in histones in the liver of normal mts and in rats irradiated with 5.7 Gy gamma rays were examined. Quantitative histone changes in growing and aging rats (from 1 to 28 months of age) were f ound to be mild only. As they paralleled the DNA changes, the histone/ DNA ratio remained stable with age. In total extracted histones there was a decrease in the H1 proportion in older age groups with preceding increase in the H1(0) proportion. Thirty minutes after irradiation th e amount of histones was reduced with age, probably due to an impaired extractability of histones. As the quantitative DNA changes were mild er, the histone/DNA ratio decreased in aging liver after irradiation. Similar patterns of changes in proportion of the H1 fraction and H1(0) subfraction were observed in irradiated and nonirradiated animals, in the former with an earlier onset. Irradiation therefore, accelerated spontaneous age-related alterations.