ALTERATIONS OF ADP-RIBOSYLATION AND DNA-BREAKS IN AGING BRAIN CELLS

Neuronal and astroglial cells were prepared from whole brain of three month and 30-month- old rats for study of alterations in the nuclear poly ADP-ribosylation and DNA breaks with age. The relative purity of the cell preparations was confirmed by the determination of the neurofilament (low molecular weight) and glutamine synthetase content of the cells using ELISA. An increase (75%) in the poly ADP-ribosylation was observed in the whole brain cell suspension of aged rats, whereas the increase was markedly pronounced (460%) when the reaction was measured in the purified neuronal preparations. The rate of poly ADP-ribosylation in the astroglial fractions prepared from aged rat brain was higher than that of adult levels (67%). An unexpectedly high increase of ADP-ribosylation in the neurons and a much lower rate in the astroglial cells was thus recorded. The amount of DNA breaks was also higher in the neuronal preparation in aged brain as compared to that of adult levels. The amount of DNA breaks was much lower in the astroglial cells and aging had no effect on DNA breaks of these cells. The close relationship between DNA breaks and poly ADP-ribosylation in the different cell types suggest that neurons are more susceptible to the metabolic alterations of the aging process