QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online July 20, 2007
Journal of Experimental Biology 210, 2607-2617 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.008078

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Stockard, T. K. Articles by Ponganis, P. J. Search for Related Content PubMed PubMed Citation Articles by Stockard, T. K. Articles by Ponganis, P. J. Social Bookmarking                         What's this?

Blood oxygen depletion during rest-associated apneas of northern elephant seals (Mirounga angustirostris)

T. K. Stockard¹, D. H. Levenson¹, L. Berg², J. R. Fransioli¹, E. A. Baranov³ and P. J. Ponganis^1,*

¹ Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, CA 92093-0204, USA
² US Naval Medical Center, Balboa Hospital, San Diego, CA 92134, USA
³ Limnological Institute, Siberian Division of Russian Academy of Sciences, Irkutsk, Russia

^* Author for correspondence (e-mail: pponganis{at}ucsd.edu)

Accepted 17 May 2007

Blood gases (P_O2, P_CO2, pH), oxygen content, hematocrit and hemoglobin concentration were measured during rest-associated apneas of nine juvenile northern elephant seals. In conjunction with blood volume determinations, these data were used to determine total blood oxygen stores, the rate and magnitude of blood O₂ depletion, the contribution of the blood O₂ store to apneic metabolic rate, and the degree of hypoxemia that occurs during these breath-holds. Mean body mass was 66±9.7 kg (± s.d.); blood volume was 196±20 ml kg^–1; and hemoglobin concentration was 23.5±1.5 g dl^–1. Rest apneas ranged in duration from 3.1 to 10.9 min. Arterial P_O2 declined exponentially during apnea, ranging between a maximum of 108 mmHg and a minimum of 18 mmHg after a 9.1 min breath-hold. Venous P_O2 values were indistinguishable from arterial values after the first minute of apnea; the lowest venous P_O2 recorded was 15 mmHg after a 7.8 min apnea. O₂ contents were also similar between the arterial and venous systems, declining linearly at rates of 2.3 and 2.0 ml O₂ dl^–1 min^–1, respectively, from mean initial values of 27.2 and 26.0 ml O₂ dl^–1. These blood O₂ depletion rates are approximately twice the reported values during forced submersion and are consistent with maintenance of previously measured high cardiac outputs during rest-associated breath-holds. During a typical 7-min apnea, seals consumed, on average, 56% of the initial blood O₂ store of 52 ml O₂ kg^–1; this contributed 4.2 ml O₂ kg^–1 min^–1 to total body metabolic rate during the breath-hold. Extreme hypoxemic tolerance in these seals was demonstrated by arterial P_O2 values during late apnea that were less than human thresholds for shallow-water blackout. Despite such low P_O2s, there was no evidence of significant anaerobic metabolism, as changes in blood pH were minimal and attributable to increased P_CO2. These findings and the previously reported lack of lactate accumulation during these breath-holds are consistent with the maintenance of aerobic metabolism even at low oxygen tensions during rest-associated apneas. Such hypoxemic tolerance is necessary in order to allow dissociation of O₂ from hemoglobin and provide effective utilization of the blood O₂ store.

Key words: blood gases, oxygen, P_O2, elephant seal, apnea

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

Related articles in JEB:

BREATHE IN...

Laura Blackburn
JEB 2007 210: ii. [Full Text]  

This article has been cited by other articles:

				D. S. Houser, L. A. Dankiewicz-Talmadge, T. K. Stockard, and P. J. Ponganis Investigation of the potential for vascular bubble formation in a repetitively diving dolphin J. Exp. Biol., January 1, 2010; 213(1): 52 - 62. [Abstract] [Full Text] [PDF]

				K. R. Olson, N. L. Whitfield, S. E. Bearden, J. St. Leger, E. Nilson, Y. Gao, and J. A. Madden Hypoxic pulmonary vasodilation: a paradigm shift with a hydrogen sulfide mechanism Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2010; 298(1): R51 - R60. [Abstract] [Full Text] [PDF]

				J. U. Meir and P. J. Ponganis High-affinity hemoglobin and blood oxygen saturation in diving emperor penguins J. Exp. Biol., October 15, 2009; 212(20): 3330 - 3338. [Abstract] [Full Text] [PDF]

				J. U. Meir, C. D. Champagne, D. P. Costa, C. L. Williams, and P. J. Ponganis Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2009; 297(4): R927 - R939. [Abstract] [Full Text] [PDF]

				P. J. Ponganis, T. K. Stockard, J. U. Meir, C. L. Williams, K. V. Ponganis, and R. Howard O2 store management in diving emperor penguins J. Exp. Biol., January 15, 2009; 212(2): 217 - 224. [Abstract] [Full Text] [PDF]

				P. J. Ponganis, U. Kreutzer, T. K. Stockard, P.-C. Lin, N. Sailasuta, T.-K. Tran, R. Hurd, and T. Jue Blood flow and metabolic regulation in seal muscle during apnea J. Exp. Biol., October 15, 2008; 211(20): 3323 - 3332. [Abstract] [Full Text] [PDF]

				P. J. Ponganis, T. K. Stockard, J. U. Meir, C. L. Williams, K. V. Ponganis, R. P. van Dam, and R. Howard Returning on empty: extreme blood O2 depletion underlies dive capacity of emperor penguins J. Exp. Biol., December 15, 2007; 210(24): 4279 - 4285. [Abstract] [Full Text] [PDF]

				L. Blackburn BREATHE IN... J. Exp. Biol., August 1, 2007; 210(15): ii - ii. [Full Text] [PDF]