Protein‐Bound Polymeric and Monomeric ADP‐Ribose Residues in Hepatic Tissues

Abstract

Determination of poly(ADP-ribose) levels was performed by a new procedure involving covalent chromatography of released polymer, degradation to phosphoribosyl AMP and quantification of this specific derivative by a radioimmunoassay. In adult rat liver, about 85 pmol polymeric ADP-ribose residues/g tissue was found. Similar values were obtained when the determination was carried out by an independent procedure not involving boronate chromatography or sedimentation of DNA. In adult rat liver, polymeric ADP-ribose residues amounted to about 1/200 of total monomeric ADP-ribose residues. Most of the polymeric ADP-ribose residues were linked to proteins by NH2OH-sensitive bonds, while mono(ADP-ribose)-protein conjugates consisted of about equal amounts of NH2OH-sensitive and NH2OH-resistant subfractions. Poly(ADP-ribose) levels immediately after birth were similar to the adult status. They decreased, however, by a factor of three at the time of most rapid post-natal liver growth (day 17). A comparison with the protein-bound monomeric ADP-ribose residues indicated independent changes, and therefore presumably independent functions of these monomeric ADP-ribose residues.