POLY(ADP-RIBOSE) POLYMERASE-ACTIVITY IN INTACT OR PERMEABILIZED LEUKOCYTES FROM MAMMALIAN-SPECIES OF DIFFERENT LONGEVITY

Poly(ADP-ribosyl)ation is a eukaryotic posttranslational protein modif ication catalyzed by poly(ADP-ribose) polymerase (PARP), a highly cons erved nuclear enzyme which uses NAD as substrate. We have previously t ested PARP activity in permeabilized mononuclear blood cells (MNC) fro m 13 mammalian species as a function of the species-specific life span . A direct and maximal stimulus of PARP activation was provided by inc luding saturating amounts of a double-stranded oligonucleotide in the PARP-reaction buffer. The data yielded a strong positive correlation b etween PARP activities and the species' maximal life spans (r = 0.84; p<<0.001). Here, we investigated the formation of poly(ADP-ribose) in living MNC from two mammalian species with widely differing longevity (rat and man) by immunofluorescence detection of poly(ADP-ribose). The fraction of positive cells was recorded, following gamma-irradiation of intact MNC, as a semiquantitative estimation of poly(ADP-ribose) fo rmation. Human samples displayed a significantly higher percentage of positivity than did those from rats, consistent with our previous resu lts on permeabilized cells. While rat MNC had a higher NAD content tha n human MNC, the number of radiation-induced DNA strand breaks was not significantly different in the two species. Since poly(ADP-ribosyl)at ion is apparently involved in DNA repair and the cellular recovery fro m DNA damage, we speculate that the higher poly(ADP-ribosyl)ation capa city of long-lived species might more efficiently help to slow down th e accumulation of unrepaired DNA damage and of genetic alterations, as compared with short-lived species.