AGE-RELATED AND PLOIDY-RELATED CHANGES IN THE NON-HISTONE PROTEINS OF RAT-LIVER NUCLEI

Hepatic nuclei from young, mature and aged rats were separated into 2n, 4n and 8n ploidy classes on sucrose gradients, and characterized in terms of DNA, RNA, histones and non-histone proteins (NHP). The absolute DNA content per nucleus doubled with each increase in ploidy as expected, and the relative proportions of other components remained uniform in all cases. Despite such overall similarity in pattern however, marked electrophoretic heterogeneity was observed among the NHP, both in relation to ploidy and animal age. All nuclei shared a common spectrum of soluble and residual NHP, but discrete variations among several specific proteins were observed. Most prominent was a systematic, age-related decrease in two major polypeptides of about 125 000 and 57 000 mol. wt, respectively. There were no comparable variations in the histone proteins. The results are discussed in terms of possible functional differentiation among hepatocytes of the various ploidy classes. © 1979.