Modulation of mitochondrial nitric oxide synthase and energy expenditure in rats during cold acclimation.
To preserve thermoneutrality, cold exposure is followed by changes in energy expenditure and basal metabolic rate (BMR). Because nitric oxide (NO) modulates mitochondrial O(2) uptake and energy levels, we analyzed cold effects (30 days at 4 degrees C) on rat liver and skeletal muscle mitochondrial NO synthases (mtNOS) and their putative impact on BMR. Cold exposure delimited two periods: A (days 1-10), with high systemic O(2) uptake and weight loss, and B (days 10-30), with lower O(2) uptake and fat deposition. mtNOS activity and expression decreased in period A and then increased in period B by 60-100% in liver and skeletal muscle (P < 0.05). Conversely, mitochondrial O(2) uptake remained initially high in the presence of l-arginine and later fell by 30-50% (P < 0.05). On this basis, the estimated fractional contribution of liver plus muscle to total BMR varied from 40% in period A to 25% in period B. The transitional modulation of mtNOS in rat cold acclimation could participate in adaptive responses that favor calorigenesis or conservative energy-saving mechanisms.
Peralta
Jorge Guillermo
JG
Laboratory of Oxygen Metabolism, University Hospital, University of Buenos Aires, Argentina. jpoderos@fmed.uba.ar
Finocchietto
Paola V
PV
Converso
Daniela
D
Schöpfer
Francisco
F
Carreras
María Cecilia
MC
Poderoso
Juan José
JJ
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001481:Basal Metabolism / Q000502:physiology; D015153:Blotting, Western; D001835:Body Weight / Q000502:physiology; D003080:Cold Temperature; D004734:Energy Metabolism / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005247:Feeding Behavior / Q000502:physiology; D005260:Female; D008929:Mitochondria, Heart / Q000201:enzymology* / Q000502:physiology*; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D005230:Fatty Acids, Nonesterified; D001120:Arginine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine