Seasonal variation of the composition of membrane lipids in liver mitochondria of the hibernator cricetus cricetus relation to intramitochondrial intermembranal protein movement

1.1. European hamster (Cricetus cricetus) raised under constant temperature conditions show a seasonal variation in the profiles of the structural fatty acids of the liver mitochondrial membrane. In these animals there are but small differences between sleeping and aroused animals in winter.2.2. The most important variation in lipid composition occurs in the prehibernating phase—at the end of summer and the beginning of autumn.3.3. However, there is no apparent coordinated relation between the seasonal variation of the composition of the fatty acids and the membrane “fluidity” as expressed by the break in the Arrhenius curve for protein release in intermembranal space of the liver mitochondria.4.4. This break occurred at a higher temperature in active animals in winter (arousedl than in summer.5.5. No general correlation could be found between the breaks in the Arrhenius curves and the variations of the different fatty acid species during the seasonal cycle, except for the most polyunsaturated fatty acid (docosahexanoic acid) where an excellent inverse correlation was observed.6.6. Our results suggest that the more fluid parts of the lipidic leaflet of the mitochondrial membrane are those more specifically involved in such phenomena as succinate induced intramitochondrial protein movement and that the changes in composition of the mitochondrial lipids are a possible adaptative advantages for the hibernator.