Fatty acid composition of tissue lipids of captive and wild brown lemmings

Abstract

1. 1. The fatty acid composition of the lipids of white adipose tissue (WAT), brown adipose tissue (BAT), skeletal muscle (MUS) and liver was determined from brown lemmings ( Lemmus trimucronatus Merriam = L. sibiricus Kerr) subjected to different conditions of captivity and from wild lemmings caught in the field at Barrow, Alaska. 2. 2. The slight changes in the fatty acid composition of WAT, BAT or MUS of captive lemmings acclimated to two different diets, two ambient temperatures (5 and 20°C) and two photoperiods (16 and 0 hr of light/24 hr) were not statistically significant. 3. 3. The fatty acid composition of the livers of captives differed with diet and with acclimation temperature becoming more unsaturated in the cold. 4. 4. There were marked seasonal differences in the fatty acid composition of WAT, BAT and liver of wild caught lemmings. Muscle was not analyzed. High amounts of linolenic acid in summer and of linoleic acid in winter may have been correlated with diet. 5. 5. There was an increase in the percentage unsaturation of the fatty acids in WAT and BAT during winter but not of those in liver. The double-bond index, indicating the degree of unsaturation, was also high in winter but remained high in summer due to large amounts of linolenic acid in the tissues.