title: Localization of cAMP-dependent signal transducers in early rat liver carcinogenesis.
abstract: Cyclic AMP (cAMP) is an important regulator of liver growth and differentiation. The main intracellular cAMP receptor, cAMP-dependent protein kinase (PKA), consists of two regulatory (R) and two catalytic (C) subunits. There are two classes, RI and RII, of the regulatory subunit, giving rise to type I (RI2C2) and type II (RII2C2) PKA. The RI/RII ratio generally decreases during organ development, and increases during carcinogenesis. Alterations in this ratio have been implicated as an important factor in experimental and clinical carcinogenesis. We have studied the expression of RIalpha, RIIalpha, Calpha, and an important substrate of PKA, the cAMP-response element binding protein, during rat liver carcinogenesis. Two-color immunofluorescence and confocal laser scan microscopy were used to characterize localization of the cAMP-dependent signal transducers in hepatocytes, bile ducts, oval cells, and preneoplastic lesions. We found that bile ducts and oval cells (putative liver stem cells) contained a higher RI/RII ratio than hepatocytes and preneoplastic lesions. Thus, an altered RI/RII ratio was not detected during early rat liver carcinogenesis, but may contribute to differentiation of putative liver stem cells to hepatocytes.
authors.affiliation: Laboratory for Toxicopathology, Institute of Pathology, The National Hospital (Rikshospitalet), University of Oslo, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Skarpen
authors.forename: G H
authors.initials: GH
authors.lastname: Thoresen
authors.forename: K
authors.initials: K
authors.lastname: Taskén
authors.forename: J T
authors.initials: JT
authors.lastname: Samuelsen
authors.forename: T
authors.initials: T
authors.lastname: Jahnsen
authors.forename: P E
authors.initials: PE
authors.lastname: Schwarze
authors.forename: H S
authors.initials: HS
authors.lastname: Huitfeldt
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000032:analysis; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000201:enzymology* / Q000473:pathology; D008113:Liver Neoplasms / Q000139:chemically induced / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008969:Molecular Sequence Data; D009374:Neoplasms, Experimental / Q000201:enzymology* / Q000473:pathology; D011506:Proteins / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction; D014452:Ubiquitins
chemical_list: D000906:Antibodies; D017362:Cyclic AMP Response Element-Binding Protein; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; C517819:PRKAR2A protein, human; C517836:Prkar1a protein, rat; C517822:Prkar2a protein, rat; D011506:Proteins; D014452:Ubiquitins; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases