Futile cycling of protons across the mitochondrial inner membrane accounts for 20 % or more of the total standard metabolic rate of a rat. Approximately 15 % of this total is due to proton leakage inside the skeletal muscle alone. This study examined whether the rate of proton leak is down-regulated as a part of a coordinated response to energy conservation during metabolic depression in cold-submerged frogs. We compared the proton leak rate of skeletal muscle mitochondria isolated from frogs at different stages of hibernation (control, 1 month and 4 months of submergence in normoxia and hypoxia). The kinetics of mitochondrial proton leak rate was unaltered throughout normoxic and hypoxic submergence. The state 4 respiration rates did not differ between control animals and frogs hibernating in normoxia. In contrast, the state 4 respiration rates obtained from frogs submerged in hypoxic water for 4 months were half those of control animals. This 50 % reduction in respiration rate in hypoxic hibernation was due to a reduction in electron transport chain activity and consequent decrease in mitochondrial membrane potential. We conclude that proton leak rate is reduced during metabolic depression as a secondary result of a decrease in electron transport chain activity, but that the proton conductance is unchanged. In addition, we show that the rate of proton leakage and the activity of the electron transport chain are lower in frogs than in rats, strengthening the observation that mitochondria from ectotherms have a lower proton conductance than mitochondria from endotherms.
REFERENCES
Boutilier
R. G.
, Donohoe
P. H.
, Tattersall
G. J.
, West
T. G.
(1997
). Hypometabolic homeostasis in overwintering aquatic amphibians
. J. Exp. Biol
200
, 387
–.Bradford
D. F.
(1983
). Winterkill, oxygen relations and energy metabolism of a submerged dormant amphibian, Rana muscosa
. Ecology
64
, 1171
–.Brand
M. D.
(1990
). The contribution of the leak of protons across the mitochondrial inner membrane to standard metabolic rate
. J. theor. Biol
145
, 267
–.Brand
M. D.
(1994
). The stoichiometry of proton pumping and ATP synthesis in mitochondria
. Biochemist
16
, 899
–.Brand
M. D.
, Brindle
K. M.
, Buckingham
J. A.
, Harper
J. A.
, Rolfe
D. F. S.
, Stuart
J. A.
(1999
). The significance and mechanism of mitochondrial proton conductance
. Int. J. Obes
23
, 4
–.Brand
M. D.
, Chien
L. F.
, Diolez
P.
(1994
). Experimental discrimination between proton leak and redox slip during mitochondrial electron transport
. Biochem. J
297
, 27
–.Brand
M. D.
, Couture
P.
, Else
P. L.
, Withers
K. W.
, Hulbert
A. J.
(1991
). Evolution of energy metabolism: proton permeability of the inner membrane of liver mitochondria is greater in a mammal than in a reptile
. Biochem. J
275
, 81
–.Brand
M. D.
, Couture
P.
, Hulbert
A. J.
(1994
). Liposomes from mammalian liver mitochondria are more polyunsaturated and leakier to protons than those from reptiles
. Comp. Biochem. Physiol
108
, 181
–.Brand
M. D.
, Murphy
M. P.
(1987
). Control of electron flux through the respiratory chain in mitochondria and cells
. Biol. Rev
62
, 141
–.Brookes
P. S.
, Buckingham
J. A.
, Tenreiro
A. M.
, Hulbert
A. J.
, Brand
M. D.
(1998
). The proton permeability of the inner membrane of liver mitochondria from ectothermic and endothermic vertebrates and from obese rats: correlations with standard metabolic rate and phospholipid fatty acid composition
. Comp. Biochem. Physiol
119
, 325
–.Brookes
P. S.
, Hulbert
A. J.
, Brand
M. D.
(1997
). The proton permeability of liposomes made from mitochondrial inner membrane phospholipids: no effect of fatty acid composition
. Biochim. Biophys. Acta
1330
, 157
–.Brookes
P. S.
, Rolfe
D. F. S.
, Brand
M. D.
(1997
). The proton permeability of liposomes made from mitochondrial inner membrane phospholipids: comparison with isolated mitochondria
. J. Membr. Biol
155
, 167
–.Brooks
S. P. J.
, Storey
K. B.
(1997
). Glycolytic controls in estivation and anoxia: a comparison of metabolic arrest in land and marine molluscs
. Comp. Biochem. Physiol
118
, 1103
–.Brustovetsky
N. N.
, Amerkhanov
Z. G.
, Popova
E. Y.
, Konstantinov
(1990
). Reversible inhibition of electron transfer in the ubiquinol cytochrome c reductase segment of the mitochondrial respiratory chain in hibernating ground squirrels
. FEBS Lett
263
, 73
–.Brustovetsky
N. N.
, Egorova
M. V.
, Iljasova
E. N.
, Bakeeva
L. E.
(1993
). Relationship between structure and function of liver mitochondria from hibernating and active ground squirrels, Citellus undulatus
. Comp. Biochem. Physiol
106
, 125
–.Brustovetsky
N. N.
, Mayevsky
E. I.
, Grishina
E. V.
, Gogvadze
V. G.
, Amerkhanov
Z. G.
(1989
). Regulation of the rate of respiration and oxidative phosphorylation in liver mitochondria from hibernating ground squirrels, Citellus undulatus
. Comp. Biochem. Physiol
94
, 537
–.Canton
M.
, Luvisetto
S.
, Schmehl
I.
, Azzone
G. F.
(1995
). The nature of mitochondrial respiration and discrimination between membrane and pump properties
. Biochem. J
310
, 477
–.Donohoe
P. H.
, Boutilier
R. G.
(1998
). The protective effects of metabolic rate depression in hypoxic cold submerged frogs
. Respir. Physiol
111
, 325
–.Donohoe
P. H.
, West
T. G.
, Boutilier
R. G.
(1998
). Respiratory, metabolic and acid—base correlates of aerobic metabolic rate reduction in overwintering frogs
. Am. J. Physiol
43
, 704
–.Dufour
S.
, Rousse
N.
, Canioni
P.
, Diolez
P.
(1996
). Top-down control analysis of temperature effect on oxidative phosphorylation
. Biochem. J
314
, 743
–.Gehnrich
S. C.
, Aprille
J. R.
(1988
). Hepatic gluconeogenesis and mitochondrial function during hibernation
. Comp. Biochem. Physiol
91
, 11
–.Gornall
A. G.
, Bardawill
C. J.
, David
M. M. J.
(1949
). Determination of serum proteins by means of the biuret reaction
. J. Biol. Chem
177
, 751
–.Guppy
M.
, Fuery
C. J.
, Flanigan
J. E.
(1994
). Biochemical principles of metabolic depression
. Comp. Biochem. Physiol
109
, 175
–.Guppy
M.
, Withers
P.
(1999
). Metabolic depression in animals; physiological perspectives and biochemical generalizations
. Biol. Rev
74
, 1
–.Hafner
R. P.
, Brand
M. D.
(1991
). Effect of protonmotive force on the relative proton stoichiometries of the mitochondrial proton pumps
. Biochem. J
275
, 75
–.Hafner
R. P.
, Nobes
C. D.
, McGown
A. D.
, Brand
M. D.
(1988
). Altered relationship between protonmotive force and respiration rate in non-phosphorylating liver mitochondria isolated from rats of different thyroid hormone status
. Eur. J. Biochem
178
, 511
–.Hand
S. C.
, Hardewig
I.
(1996
). Downregulation of cellular metabolism during environmental stress: mechanisms and implications
. Annu. Rev. Physiol
58
, 539
–.Hochachka
P. W.
, Land
S. C.
, Buck
L. T.
(1997
). Oxygen sensing and signal transduction in metabolic defense against hypoxia: lessons from vertebrate facultative anaerobes
. Comp. Biochem. Physiol
118
, 23
–.Kwast
K. E.
, Hand
S. C.
(1996
). Acute depression of mitochondrial protein synthesis during anoxia: contributions of oxygen sensing, matrix acidification and redox state
. J. Biol. Chem
271
, 7313
–.Liu
C. C.
, Frehn
J. L.
, LaPorta
A. D.
(1969
). Liver and brown fat mitochondrial response to cold in hibernators and nonhibernators
. J. Appl. Physiol
27
, 83
–.Pehowich
D. J.
, Wang
L. C. H.
(1984
). Seasonal changes in mitochondrial succinate dehydrogenase activity in a hibernator, Spermophilus richardsonii
. J. Comp. Physiol
154
, 495
–.Porter
R. K.
, Brand
M. D.
(1993
). Body mass dependence of H+leak in mitochondria and its relevance to metabolic rate
. Nature
362
, 628
–.Porter
R. K.
, Hulbert
A. J.
, Brand
M. D.
(1996
). Allometry of mitochondrial proton leak: influence of membrane surface area and fatty acid composition
. Am. J. Physiol
271
, 1550
–.Ramsey
J. J.
, Johnson
D. E.
, Hossner
K. L.
, Johnson
K. A.
(1996
). Metabolic rate, organ mass and mitochondrial proton leak variations in lean and obese rats
. Comp. Biochem. Physiol
113
, 461
–.Rolfe
D. F. S.
, Brand
M. D.
(1996
). Contribution of mitochondrial proton leak to skeletal muscle respiration and to standard metabolic rate
. Am. J. Physiol
271
, 1380
–.Rolfe
D. F. S.
, Brown
G. C.
(1997
). Cellular energy utilization and molecular origin of standard metabolic rate in mammals
. Physiol. Rev
77
, 731
–.Rolfe
D. F. S.
, Hulbert
A. J.
, Brand
M. D.
(1994
). Characteristics of mitochondrial proton leak and control of oxidative phosphorylation in the major oxygen-consuming tissues of the rat
. Biochim. Biophys. Acta
1188
, 405
–.Rolfe
D. F. S.
, Newman
J. M. B.
, Buckingham
J. A.
, Clark
M. G.
, Brand
M. D.
(1999
). Contribution of mitochondrial proton leak to respiration rate in working skeletal muscle and liver and to SMR
. Am. J. Physiol
276
, 692
–.Staples
J. F.
, Hochachka
P. W.
(1997
). Liver energy metabolism during hibernation in the golden-mantled ground squirrel, Spermophilus lateralis
. Can. J. Zool
74
, 1059
–.Storey
K. B.
(1997
). Metabolic regulation in mammalian hibernation: enzyme and protein adaptations
. Comp. Biochem. Physiol
118
, 1115
–.Storey
K. B.
, Storey
J. M.
(1990
). Metabolic rate depression and biochemical adaptation in anaerobiosis, hibernation and estivation
. Q. Rev. Biol
65
, 145
–.Stuart
J. A.
, Gillis
T. E.
, Ballantyne
J. S.
(1998
). Compositional correlates of metabolic depression in the mitochondrial membrane of estivating snails
. Am. J. Physiol
44
, 1977
–.Stuart
J. A.
, Gillis
T. E.
, Ballantyne
J. S.
(1998
). Remodeling of phospholipid fatty acids in mitochondrial membranes of estivating snails
. Lipids
33
, 787
–.
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