Increased purine nucleotide binding, altered polypeptide composition, and thermogenesis in brown adipose tissue mitochondria of cold-acclimated rats.

Rapid increases in atractyloside-insensitive binding of purine nucleotides (ADP or GDP) and in a polypeptide of 32 000 occur in brown adipose tissue mitochondria of the rat during acclimation to cold. The increased binding is apparent within 1 h and reaches a maximum after 3--7 days of exposure to 4 degrees C. The increase in the 32 000 peptide occurs more slowly and reaches a maximum after 2--3 weeks. There is a simultaneous decrease in a polypeptide of 96 000, apparent after 1 day and reaching a maximum after 1--2 weeks. Results are interpreted in terms of the appearance of an increased amount of the purine nucleotide-sensitive proton conductance pathway in association with the development of an enhanced thermogenic capacity of brown adipose tissue mitochondria during acclimation of the rat to cold.