TY - JOUR
T1 - Regulation of blood oxygen transport in hibernating mammals
AU - Revsbech, Inge G.
AU - Fago, Angela
PY - 2017/7
Y1 - 2017/7
N2 - Along with the periodic reductions in O-2 requirements of mammalian hibernators during winter, the O-2 affinity of the blood of mammalian hibernators is seasonally regulated to help match O-2 supply to consumption, contributing to limit tissue oxidative stress, particularly at arousals. Specifically, mammalian hibernators consistently show an overall increase in the blood-O-2 affinity, which causes a decreased O-2 unloading to tissues, while having similar or lower tissue O-2 tensions during hibernation. This overview explores how the decreased body temperature and concentration of red blood cell 2,3-diphosphoglycerate (DPG) that occur in hibernation contribute separately or in combination to the concurrent increase in the O-2 affinity of the hemoglobin, the O-2 carrier protein of the blood. Most mammalian hemoglobins are responsive to changes in DPG concentrations, including that of the hibernating brown bear, although the smaller hibernators, such as golden-mantled ground squirrel, chipmunks, and dormice, have hemoglobins with low sensitivity to DPG. While the effect of DPG on oxygenation may vary, the decrease in body temperature invariably increases hemoglobin's O-2 affinity in all hibernating species. However, the temperature sensitivity of hemoglobin oxygenation is low in hibernators compared to human, apparently due in part to endothermic allosteric quaternary transition in ground squirrels and dissociation of chloride ions in brown bears. A low heat of blood oxygenation in temporal heterotherms, like hibernators, may thus contribute to reduce heat loss, as found in regional heterotherms, like polar mammals, although the significance would be low in winter hibernation.
AB - Along with the periodic reductions in O-2 requirements of mammalian hibernators during winter, the O-2 affinity of the blood of mammalian hibernators is seasonally regulated to help match O-2 supply to consumption, contributing to limit tissue oxidative stress, particularly at arousals. Specifically, mammalian hibernators consistently show an overall increase in the blood-O-2 affinity, which causes a decreased O-2 unloading to tissues, while having similar or lower tissue O-2 tensions during hibernation. This overview explores how the decreased body temperature and concentration of red blood cell 2,3-diphosphoglycerate (DPG) that occur in hibernation contribute separately or in combination to the concurrent increase in the O-2 affinity of the hemoglobin, the O-2 carrier protein of the blood. Most mammalian hemoglobins are responsive to changes in DPG concentrations, including that of the hibernating brown bear, although the smaller hibernators, such as golden-mantled ground squirrel, chipmunks, and dormice, have hemoglobins with low sensitivity to DPG. While the effect of DPG on oxygenation may vary, the decrease in body temperature invariably increases hemoglobin's O-2 affinity in all hibernating species. However, the temperature sensitivity of hemoglobin oxygenation is low in hibernators compared to human, apparently due in part to endothermic allosteric quaternary transition in ground squirrels and dissociation of chloride ions in brown bears. A low heat of blood oxygenation in temporal heterotherms, like hibernators, may thus contribute to reduce heat loss, as found in regional heterotherms, like polar mammals, although the significance would be low in winter hibernation.
KW - 2,3-Diphosphoglycerate
KW - Allosteric effects
KW - Enthalpy of oxygenation
KW - Metabolic depression
KW - Hemoglobin-oxygen affinity
KW - Hibernation
KW - BEAR URSUS-ARCTOS
KW - LOWLAND DEER MICE
KW - GROUND-SQUIRRELS
KW - ORGANIC-PHOSPHATES
KW - HEMOGLOBIN-FUNCTION
KW - BODY-TEMPERATURE
KW - BROWN BEARS
KW - RESPIRATORY PROPERTIES
KW - METABOLIC SUPPRESSION
KW - ALLOSTERIC REGULATION
U2 - 10.1007/s00360-017-1085-6
DO - 10.1007/s00360-017-1085-6
M3 - Journal article
C2 - 28324160
SN - 0174-1578
VL - 187
SP - 847
EP - 856
JO - Journal of Comparative Physiology B: Biochemical, Systems, and Environmental Physiology
JF - Journal of Comparative Physiology B: Biochemical, Systems, and Environmental Physiology
IS - 5-6
T2 - 15th International Hibernation Symposium
Y2 - 31 July 2016 through 4 August 2016
ER -