title: Photic regulation of heme oxygenase activity in the golden hamster retina: involvement of dopamine.
abstract: The photic regulation of heme oxygenase (HO) activity was examined in the golden hamster retina. This enzymatic activity was significantly higher at midday than at midnight. When the hamsters were placed under constant darkness for 48 h and killed at subjective day or at subjective night, the differences in HO activity disappeared. Western blot analysis showed no differences in HO levels among these time points. Dopamine significantly increased this activity in retinas excised at noon or at midnight, with a higher sensitivity at night. The effect of dopamine was reversed by SCH 23390 but not by spiperone and clozapine and it was not reproduced by quinpirole. In vitro, the increase in HO activity found in retinas incubated under light for 1 h was significantly reduced by SCH 23390. Two cAMP analogs increased HO activity and their effect, as well as the effect of dopamine was blocked by H-89, a protein kinase A (PKA) inhibitor. Tin protoporphyrin IX, an HO inhibitor, significantly decreased cGMP accumulation with maximal effects during the day. Low concentrations of bilirubin decreased retinal thiobarbituric acid substances levels (an index of lipid peroxidation) in basal conditions and after exposing retinal cells to H2O2. These results suggest that hamster retinal HO activity is regulated by the photic stimulus, probably through a dopamine/cAMP/PKA dependent pathway.
authors.affiliation: Laboratorio de Neuroquímica Retiniana y Oftalmología Experimental, Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.
authors.forename: Geraldine B
authors.initials: GB
authors.lastname: Sacca
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Sáenz
authors.forename: Carolina O
authors.initials: CO
authors.lastname: Jaliffa
authors.forename: Luciana
authors.initials: L
authors.lastname: Minces
authors.forename: María I
authors.initials: MI
authors.lastname: Keller Sarmiento
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Rosenstein
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D001663:Bilirubin / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002940:Circadian Rhythm / Q000502:physiology; D003024:Clozapine / Q000494:pharmacology; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008647:Mesocricetus; D017440:Photoperiod; D019257:Quinpirole / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013134:Spiperone / Q000494:pharmacology; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D017392:Thiobarbituric Acid Reactive Substances; D019257:Quinpirole; D013134:Spiperone; D003994:Bucladesine; D006419:Heme Oxygenase (Decyclizing); D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP; D003024:Clozapine; D001663:Bilirubin; D004298:Dopamine