The acute regulation of mitochondrial proton conductance in cells and mitochondria from the brown fat of cold-adapted and warm-adapted guinea pigs.
Cells and mitochondria were prepared from the brown adipose tissue of adult guinea-pigs adapted to either 4-7 degrees C or 22-25 degrees C. The cold-adapted cells displayed noradrenaline-stimulated, propranolol-sensitive respiration, but noradrenaline failed to increase the respiration of the warm-adapted cells. Purine-nucleotide-sensitive proton conductance was greater in cold-adapted mitochondria than in warm-adapted controls. At the same time cold-adapted mitochondria were extremely sensitive to the uncoupling effect of endogenous and infused fatty acids, and resembled the mitochondria from the brown adipose tissue of cold-adapted hamsters. Warm-adapted mitochondria were ninefold less sensitive, and resembled liver mitochondria. With cold-adapted, but not warm-adapted mitochondria, respiration increased proportionately to the rate of fatty acid infusion. It is concluded that the presence of the 32000-Mr proton conductance pathway is necessary for the expression of a high sensitivity to fatty acid uncoupling, suggesting that the fatty acids interact directly with this protein to modulate the proton conductance during the acute regulation of thermogenesis.
D000064:Acclimatization; D002001:Adipose Tissue, Brown / Q000502:physiology*; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects; D003080:Cold Temperature; D004553:Electric Conductivity; D005227:Fatty Acids / Q000494:pharmacology / Q000502:physiology*; D006168:Guinea Pigs; D006358:Hot Temperature; D066298:In Vitro Techniques; D008928:Mitochondria / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D011522:Protons
D005227:Fatty Acids; D011522:Protons; D009638:Norepinephrine