title: Circadian heme oxygenase activity in the hamster suprachiasmatic nuclei.
abstract: Entrainment of mammalian circadian rhythms requires the activation of specific signal transduction pathways in the hypothalamic suprachiasmatic nuclei (SCN). We have tested the participation of heme oxygenase (HO) in the SCN, by assessing HO specific activity at different time points and photic conditions. HO activity was determined by the conversion of hemin to bilirubin. HO enzymatic activity in the SCN was significantly higher during the night than during the day; this difference persisted when animals were placed under constant darkness, suggesting an endogenous circadian control. HO inhibition by Zn-protoporphyrin did not affect light-induced phase shifts in vivo, suggesting that the enzyme is not necessary for light input to the clock.
authors.affiliation: Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, R.S. Peña 180, Bernal, 1876 Buenos Aires, Argentina.
authors.forename: María Fernanda
authors.initials: MF
authors.lastname: Rubio
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Agostino
authors.forename: Gabriela A
authors.initials: GA
authors.lastname: Ferreyra
authors.forename: Diego A
authors.initials: DA
authors.lastname: Golombek
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001663:Bilirubin / Q000378:metabolism; D015153:Blotting, Western; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D006224:Cricetinae; D003624:Darkness; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D009043:Motor Activity / Q000187:drug effects; D010775:Photic Stimulation; D011524:Protoporphyrins / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000201:enzymology*; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D011524:Protoporphyrins; C017803:zinc protoporphyrin; D006419:Heme Oxygenase (Decyclizing); D001663:Bilirubin