title: Effects of hypoxia and hypercapnia on aerobic metabolic processes in northern elephant seals.
abstract: An hypoxia-induced metabolic down-regulation has been implicated as an important protective mechanism against tissue deoxygenation in mammals. Whether the same response to hypoxia occurs in northern elephant seals was studied. The effects of hypercapnia were also examined to determine whether the reduced ventilatory response of seals to CO2 is associated with an analogous protective metabolic down-regulation. Thirty three seals (7-300-days-old) were studied using open-flow respirometry with simultaneous monitoring of apnea frequencies and heart rates. Hypoxia (11% O2) and hypercapnia (7% CO2) caused increases in metabolism of up to 38% with corresponding decreases in the percent time spent apneic (%AP) and increases in heart rate. The metabolic, breathing and heart rate responses to altered inspired gases were independent of age. Metabolism was strongly negatively correlated with %AP suggesting that elevated metabolism during hypoxia and hypercapnia exposure is attributable to decreases in %AP. In young elephant seals metabolic down-regulation is not an automatic protective response to experimentally-imposed hypoxia or hypercapnia.
authors.affiliation: Department of Biology and Institute of Marine Science, University of California at Santa Cruz, 95064, USA. skohin@ucsd.edu
authors.forename: S
authors.initials: S
authors.lastname: Kohin
authors.forename: T M
authors.initials: TM
authors.lastname: Williams
authors.forename: C L
authors.initials: CL
authors.lastname: Ortiz
mesh_terms: D000332:Aerobiosis; D000375:Aging / Q000502:physiology; D000818:Animals; D000833:Animals, Suckling; D002245:Carbon Dioxide / Q000378:metabolism; D004242:Diving / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006935:Hypercapnia / Q000378:metabolism* / Q000503:physiopathology; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D015656:Respiratory Mechanics / Q000502:physiology; D046048:Seals, Earless / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide