title: Hydrogen peroxide generation by monoamine oxidases in rat white adipocytes: role on cAMP production.
abstract: In rat, white adipocytes monoamine oxidases (EC 1.4.3.4.) generate hydrogen peroxide (H(2)O(2)). Recent studies suggested that, in addition to its toxic features, H(2)O(2) may behave as a cell second messenger. In the present study, using fluorimetric and chemiluminescence (CL) assays, we showed that tyramine degradation by monoamine oxidases in intact adipocytes resulted in the concentration-dependent generation of H(2)O(2). In addition, we found that, in the presence of low tyramine concentrations, forskolin-dependent cAMP production was significantly increased as compared to that of the control and this increase was prevented by the monoamine oxidase inhibitor pargyline or by the H(2)O(2) trapping system homovanillic acid-peroxidase. Finally, we demonstrated that tyramine degradation by monoamine oxidases increased the ability of isoproterenol to induce cell lipolysis. Taken together, these data suggest that H(2)O(2) produced during substrate degradation by monoamine oxidases may participate in the regulation of adipocyte metabolism.
authors.affiliation: Department of Pharmacology, University of Florence, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Raimondi
authors.forename: G
authors.initials: G
authors.lastname: Banchelli
authors.forename: L
authors.initials: L
authors.lastname: Sgromo
authors.forename: R
authors.initials: R
authors.lastname: Pirisino
authors.forename: M
authors.initials: M
authors.lastname: Ner
authors.forename: A
authors.initials: A
authors.lastname: Parini
authors.forename: C
authors.initials: C
authors.lastname: Cambon
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002250:Carbon Radioisotopes; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005990:Glycerol / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012663:Semicarbazides / Q000494:pharmacology; D014439:Tyramine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D002250:Carbon Radioisotopes; D008996:Monoamine Oxidase Inhibitors; D012663:Semicarbazides; D005576:Colforsin; C010059:carbamylhydrazine; D010293:Pargyline; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; D008995:Monoamine Oxidase; D007545:Isoproterenol; D005990:Glycerol; D014439:Tyramine