title: Poly(ADP-ribose) polymerase is affected early by thyroid state during liver regeneration in rats.
abstract: Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme involved in DNA synthesis, DNA repair, and cell replication and transformation, also plays a role in the early steps of liver regeneration induced by partial hepatectomy (PH). PARP and DNA topoisomerase I (Topo I) activities and de novo DNA synthesis were studied during liver regeneration in rats with altered thyroid state. Hepatic PARP activity, evaluated as [(32)P]NAD incorporated into isolated liver nuclei, was inhibited in hyperthyroid rats and increased in hypothyroid animals. In both euthyroid and hyperthyroid rats PARP activity was rapidly stimulated, peaking 6 h after PH. In hypothyroid animals, an early decrease in activity was found, at a minimum of 6 h after PH, followed by an early onset of DNA synthesis. An inverse relationship between PARP and Topo I activities was a shared feature among euthyroid, hypothyroid, and hyperthyroid rats. Together these data show that, in replicating hepatocytes, thyroid hormones exert a regulatory role on PARP activity, which reflects the control of a number of nuclear proteins involved in DNA metabolism.
authors.affiliation: Department of Physiological, Biochemical, and Cellular Sciences, Faculty of Science, University of Sassari, 07100 Sassari, Italy. cesarone@ssmain.uniss.it
authors.forename: C F
authors.initials: CF
authors.lastname: Cesarone
authors.forename: L
authors.initials: L
authors.lastname: Scarabelli
authors.forename: I
authors.initials: I
authors.lastname: Demori
authors.forename: S
authors.initials: S
authors.lastname: Balocco
authors.forename: E
authors.initials: E
authors.lastname: Fugassa
mesh_terms: D000818:Animals; D004261:DNA Replication; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D007037:Hypothyroidism / Q000150:complications / Q000503:physiopathology; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000502:physiology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D011065:Poly(ADP-ribose) Polymerases; D004264:DNA Topoisomerases, Type I; D013974:Thyroxine