Age-related alteration of poly(ADP-ribose) polymerase activity in different parts of the brain

Poly(ADP-ribose) polymerase (PARP) is a conserved enzyme involved in the re gulation of DNA repair and genome stability. The role of PARP during aging is not well known. In this study PARP activity was investigated in nuclear fractions from hippocampus, cerebellum, and cerebral cortex of adult (4 mon ths), old adult (14 months) and aged (24-27 months) rats. Concomitantly, th e free radical evoked lipid peroxidation was estimated as thiobarbituric ac id reactive substances (TBARS). The specific activity of PARP in adult brain was about 25, 21 and 16 pmol/m g protein per min in hippocampus, cerebellum and cerebral cortex, respectiv ely. The enzyme activity was higher in all investigated parts of the brain of old adults. In aged animals PARP activity was lower in hippocampus by ab out 50%, and was unchanged in cerebral cortex and in cerebellum comparing t o adult rats. The concentration of TEARS was the same in all parts of the b rain and remained unchanged during aging. There is no direct correlation be tween PARP activity and free radical evoked Lipid peroxidation during brain aging. The lowered enzyme activity in aged hippocampus may decrease DNA re pair capacity which subsequently may be responsible for the higher vulnerab ility of hippocampal neurons to different toxic insults.