Metabolic depression and enhanced O(2) affinity of mitochondria in hypoxic hypometabolism.
This study examined whether the steady-state hypometabolism seen in overwintering frogs (Rana temporaria) is reflected at the mitochondrial level either by a reduction in their resting (state 4) and active (state 3) respiration rates and/or by increases in O(2) affinity. We isolated mitochondria from the skeletal muscle of cold-submerged frogs at different stages during their hibernation in normoxic and hypoxic water. A modest metabolic depression at the whole animal level (normoxic submergence) was not associated with a reduction in mitochondrial state 4 and state 3 respiration rates. However, mitochondria isolated from frogs that were submerged for 1 mo manifested an increase in their O(2) affinity compared with controls and with animals submerged for 4 mo. Hypometabolism was more pronounced at the whole animal level during hypoxic submergence and was accompanied by 1) a reduction in mitochondrial state 4 and state 3 rates and 2) an increase in the O(2) affinity of mitochondria. These findings demonstrate that metabolic depression can be reflected at all levels of biological organization in hypoxia-tolerant animals.
St-Pierre
J
J
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom. js264@cam.ac.uk
Tattersall
G J
GJ
Boutilier
R G
RG
D000818:Animals; D003080:Cold Temperature; D006605:Hibernation / Q000502:physiology*; D000860:Hypoxia; D007700:Kinetics; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D010101:Oxygen Consumption; D011896:Rana temporaria