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Huff and Puff or Shut'er Down: Hypoxia‐Tolerant Mammals Respond Differently to Low Oxygen
Author(s) -
Dzal Yvonne,
Pamenter Matthew,
Faure Paul,
Milsom William
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.686.3
Subject(s) - hypoxia (environmental) , oxygen , mole , ventilation (architecture) , biology , zoology , medicine , ecology , chemistry , biochemistry , mechanical engineering , organic chemistry , engineering
Unlike most mammals, ground squirrels ( Ictidomys tridecemlineatus ), mole rats ( Heterocephalus glaber ), and bats ( Eptesicus fuscus ) are exceptionally tolerant of low oxygen (i.e. hypoxia). Unfortunately, the basis of this tolerance is not well understood. To elucidate the underlying mechanisms these animals use to match oxygen supply to demand under hypoxic conditions, we exposed animals to progressive reductions in inspired oxygen (21, 12, 9, 7, and 5% O 2 ) at an ambient temperature within their thermoneutral zone, and measured their metabolic, thermoregulatory, and ventilatory responses. Severe hypoxia (5% O 2 ) led to a profound depression in oxygen demand in mole rats (>85%), and bats (>65%), driven by a reduction in metabolism independent of decreases in body temperature. Mole rats and bats met these reduced demands with a combination of reductions in ventilation (45% and 20%, respectively) and increases in the amount of oxygen extracted per breath (40% and 25%, respectively). Unlike mole rats and bats, ground squirrels did not reduce oxygen demand or body temperature in hypoxia; instead they increased oxygen supply through an increase in ventilation (>250%) with no change in the amount of oxygen extracted per breath. Our results suggest that while ground squirrels match oxygen supply to demand in severe hypoxia by a brisk ventilatory response, mole rats and bats do so by reducing metabolic demands, indicating that these species employ divergent strategies to tolerate hypoxia.