title: Metabolic effects of carbenoxolone in rat liver.
abstract: The action of carbenoxolone on hepatic energy metabolism was investigated in the perfused rat liver and isolated mitochondria. In perfused livers, carbenoxolone (200-300 microM) increased oxygen consumption, glucose production and glycolysis from endogenous glycogen. Gluconeogenesis from lactate or fructose, an energy-dependent process, was inhibited. This effect was already evident at a concentration of 25 microM. The cellular ATP levels and the adenine nucleotide content were decreased by carbenoxolone, whereas the AMP levels were increased. In isolated mitochondria, carbenoxolone stimulated state IV respiration and decreased the respiratory coefficient with the substrates beta-hydroxybutyrate and succinate. The ATPase of intact mitochondria was stimulated, the ATPase of uncoupled mitochondria was inhibited, and the ATPase of disrupted mitochondria was not altered by carbenoxolone. These results indicate that carbenoxolone acts as an uncoupler of oxidative phosphorylation and, possibly, as an inhibitor of the ATP/ADP exchange system. The inhibitory action of carbenoxolone on mitochondrial energy metabolism could be contributing to induce the mitochondrial permeability transition (MPT), a key phenomenon in apoptosis. The results of the present study can explain, partly at least, the in vivo hepatotoxic actions of carbenoxolone that were found in a previous clinical evaluation.
authors.affiliation: Laboratory of Liver Metabolism, Department of Biochemistry, University of Maringá, 87020900 Maringá, Brazil.
authors.forename: Leandro Silva
authors.initials: LS
authors.lastname: Pivato
authors.forename: Rodrigo Polimeni
authors.initials: RP
authors.lastname: Constantin
authors.forename: Emy L
authors.initials: EL
authors.lastname: Ishii-Iwamoto
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Kelmer-Bracht
authors.forename: Nair Seiko
authors.initials: NS
authors.lastname: Yamamoto
authors.forename: Jorgete
authors.initials: J
authors.lastname: Constantin
authors.forename: Adelar
authors.initials: A
authors.lastname: Bracht
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002229:Carbenoxolone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects*; D005943:Gluconeogenesis / Q000187:drug effects; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000255:Adenosine Triphosphate; D002229:Carbenoxolone