title: A comparison of blood nitric oxide metabolites and hemoglobin functional properties among diving mammals.
abstract: The ability of marine mammals to hunt prey at depth is known to rely on enhanced oxygen stores and on selective distribution of blood flow, but the molecular mechanisms regulating blood flow and oxygen transport remain unresolved. To investigate the molecular mechanisms that may be important in regulating blood flow, we measured concentration of nitrite and S-nitrosothiols (SNO), two metabolites of the vasodilator nitric oxide (NO), in the blood of 5 species of marine mammals differing in their dive duration: bottlenose dolphin, South American sea lion, harbor seal, walrus and beluga whale. We also examined oxygen affinity, sensitivity to 2,3-diphosphoglycerate (DPG) and nitrite reductase activity of the hemoglobin (Hb) to search for possible adaptive variations in these functional properties. We found levels of plasma and red blood cells nitrite similar to those reported for terrestrial mammals, but unusually high concentrations of red blood cell SNO in bottlenose dolphin, walrus and beluga whale, suggesting enhanced SNO-dependent signaling in these species. Purified Hbs showed similar functional properties in terms of oxygen affinity and sensitivity to DPG, indicating that reported large variations in blood oxygen affinity among diving mammals likely derive from phenotypic variations in red blood cell DPG levels. The nitrite reductase activities of the Hbs were overall slightly higher than that of human Hb, with the Hb of beluga whale, capable of longest dives, having the highest activity. Taken together, these results underscore adaptive variations in circulatory NO metabolism in diving mammals but not in the oxygenation properties of the Hb.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: angela.fago@bios.au.dk.
authors.forename: Angela
authors.initials: A
authors.lastname: Fago
authors.affiliation: Fundación Oceanografic, Ciudad de las Artes y las Ciencias, 46013 Valencia, Spain. Electronic address: dgarcia@oceanografic.org.
authors.forename: Daniel Garcia
authors.initials: DG
authors.lastname: Parraga
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: elinep@bios.au.dk.
authors.forename: Elin E
authors.initials: EE
authors.lastname: Petersen
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: niels32167@gmail.com.
authors.forename: Niels
authors.initials: N
authors.lastname: Kristensen
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: leagiouri@hotmail.com.
authors.forename: Lea
authors.initials: L
authors.lastname: Giouri
authors.affiliation: Department of Biology, University of Southern Denmark, 5230 Odense M, Denmark. Electronic address: fbj@biology.sdu.dk.
authors.forename: Frank B
authors.initials: FB
authors.lastname: Jensen
mesh_terms: D000818:Animals; D050643:Beluga Whale / Q000097:blood* / Q000502:physiology*; D010872:Caniformia / Q000097:blood* / Q000502:physiology*; D004242:Diving / Q000502:physiology*; D004289:Dolphins / Q000097:blood / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D009569:Nitric Oxide / Q000097:blood; D046070:Sea Lions / Q000097:blood / Q000502:physiology; D046048:Seals, Earless / Q000097:blood / Q000502:physiology; D013045:Species Specificity; D014856:Walruses / Q000097:blood / Q000502:physiology
chemical_list: D006454:Hemoglobins; D009569:Nitric Oxide
keywords: 2,3-diphosphoglycerate; Adaptation; Diving; Hypoxia; Nitrite; Oxygen; Respiration; S-nitrosation; Signaling