Circum-annual changes in triglyceride fatty acids of bat brown adipose tissue.

A circum-annual study of the fatty acids of brown adipose tissue triglycerides ofEptesicus fuscus has demonstrated a rhythmic pattern of change. This is seen as a reciprocal shift of the levels of oleic and linoleic acids. Oleic acid levels are lower during the summer months and higher in the winter months. Levels of palmitic and linoleic acids reach maximal values in midsummer and fall significantly during the winter.Homogenates of brown adipose tissue produce more(14)CO(2) from 1-(14)C-palmitic acid than from 1-(14)C-oleic acid when incubated at temperatures below 20C. The formation of(14)CO(2) from either substrate was maximal in the neighborhood of 30C, and the temperature effect was enhanced by stimulation with DL-carnitine.It is proposed that the rhythmic change in brown adipose tissue triglyceride composition is a reflection of the different rates of fatty acid oxidation and the absence of normal food intake for extended periods of time.