title: Role of endogenous carbon monoxide in the control of breathing in zebrafish (Danio rerio).
abstract: Carbon monoxide (CO) is a gaseous signaling molecule and is produced in vivo from the intracellular breakdown of heme via the heme oxygenase (HO) family of enzymes. In this study we investigated the role of the HO-1/CO system in the control of ventilation in zebrafish, Danio rerio Immunohistochemistry revealed the presence of HO-1 in the chemoreceptive neuroepithelial cells (NECs) of larvae (4 days postfertilization) and adults, indicating the potential for endogenous CO production in the NECs. Hypoxia (20 min, water Po2of 30 mmHg) caused a significant increase in HO-1 activity in whole larvae and in the gills of adult fish. Zebrafish with reduced HO-1 activity (via HO-1 knockdown in larvae or zinc protoporphyrin IX treatment in adults) exhibited increased ventilation frequency (Vf) under normoxic but not hypoxic conditions. The addition of exogenous CO restored resting Vfin fish with diminished CO production, and in some cases (e.g., hypoxic sham larvae) CO modestly reduced Vfbelow resting levels. Larval fish were treated with phenylhydrazine (PHZ) to eliminate the potential confounding effects of CO-hemoglobin interactions that might influence ventilation. PHZ treatment did not cause changes in Vfof normoxic larvae, and the addition of CO to PHZ-exposed larvae resulted in a significant decrease in sham and HO-1-deficient fish under normoxic conditions. This study demonstrates for the first time that CO plays an inhibitory role in the control of breathing in larval and adult zebrafish.
authors: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada vtzan032@uottawa.ca.
authors: Velislava
authors: V
authors: Tzaneva
authors: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
authors: Steve F
authors: SF
authors: Perry
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D005880:Gills / Q000502:physiology*; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology; D012119:Respiration; D015027:Zebrafish / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D051547:Heme Oxygenase-1
keywords: carbon monoxide; chemoreception; heme oxygenase-1; hypoxia; neuroepithelial cells; ventilation frequency