Phospholipid and fatty acid composition of frog (Rana esculenta) liver—a circannual study

Liver lipid composition of the frog Rana esculenta was examined on a circannual basis. In particular, phospholipid and cholesterol content, relative phospholipid distribution, and fatty acid patterns have been studied. Seasonal acclimatization is associated with significant modifications of phospholipid content and of the relative proportion of phospholipid classes, while cholesterol level is unchanged throughout the year. In regard to the fatty acid composition of total phospholipids as well as of the four major phospholipid classes—phosphatidylcholine (PC); phosphatidylethanolamine (PE); sphingomyelin (SM); phosphatidylserine (PS)—it appears that the liver of “summer animals” is characterized by a higher unsaturation index due to a decrease of saturated fatty acids and to an increased content of n−3 and n−6 polyunsaturated fatty acids. The results suggest that relevant compositional changes occur mainly in spring and autumn: these changes could be interpreted as being the result of both a nutritionally‐ and thermally‐induced seasonal adaptation directed toward the preservation of membrane‐associated physiological activities that are linked to the transition from the active to the inactive state of the animal.