Hamster Brown‐Adipose‐Tissue Mitochondria

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Abstract
The specific ability of fatty acids to increase the proton conductance of the inner membrane of mitochondria from the liver and brown adipose tissue of cold-adapted hamsters was compared. The liver and brown-adipose-tissue mitochondria had their effective proton conductances increased by, respectively, 0.028 and 0.94 nmol H+ .cntdot. min-1.cntdot. (mV of proton electrochemical gradient)-1 for each nmol of palmitate bound. No difference could be detected between the abilities of liver and brown-adipose-tissue mitochondria to bind fatty acids. Purine nucleotides did not displace fatty acids from the brown-adipose-tissue mitochondria. The endogenous fatty acid content of hamster brown-adipose-tissue mitochondria prepared in the absence of albumin was equivalent to 17 .+-. 7 nmol of palmitate/mg protein. The fatty content was reduced to 1 nmol/mg after preincubation of the mitochondria with CoA, ATP and carnitine. No inert pool of fatty acids could be detected. The endogenous fatty acids of hamster liver mitochondria were less than 4 nmol of palmitate equivalent/mg protein. Some of the fatty acid associated with the brown-adipose-tissue mitochondria originates during preparation of the mitochondria. The physiological role of fatty acids in controlling the proton conductance of the brown-adipose-tissue mitochondrial inner membrane, and hence non-shivering thermogenesis, is re-evaluated.