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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Brown fat mitochondria obtained from a hibernator, the golden hamster, were investigated in order to elucidate the significance of membrane permeability for metabolic functioning at different temperatures. The mitochondria were shown to have active permeases for phosphate and pyruvate, but very poorly developed permeases for di- and tricarboxylate substrate anions. This was shown with both osmotic swelling techniques and respiration-driven uptake studies. It was shown that the very limited malate permeation observed was compatible with it being a non-carrier-mediated diffusion process. The role of malate transport in supporting fatty-acid oxidation in vitro as a function of temperature was studied in detail. The results support our earlier suggestion that physiologically pyruvate carboxylase probably functions to generate oxaloacetate when high concentrations of condensing partner are needed during thermogenesis. They may also explain earlier observations that acetate was produced from palmitoyl-carnitine at low temperatures even when malate was present; this is here shown to be due to the limited malate permeability at these low temperatures. Thus, even at the body temperature of the hibernating hamster (4-5 degrees C), brown fat is probably able to combust fatty acids totally.
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PMID:Metabolic consequences of limited substrate anion permeability in brown fat mitochondria from a hibernator, the golden hamster. 646 55

Brown-adipose tissue mitochondria of hamster and rat contain phosphoenolpyruvate carboxykinase (EC 4.1.1.32). In the presence of ketoglutarate and malate, phosphoenolpyruvate is formed and exported from mitochondria. Phosphoenolpyruvate formation is inhibited by 1,2,3-benzenetricarboxylate. It is proposed that phosphoenolpyruvate carboxykinase together with pyruvate carboxylase and pyruvate kinase forms a phosphoenolpyruvate shuttle through which energy produced by the Krebs cycle in mitochondria may be exported to cytosol.
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PMID:Phosphoenolpyruvate shuttle--transport of energy from mitochondria to cytosol. 686 29