Temperature mediated restructuring of phosphatidylethanoloamines in livers of freshwater fishes

Abstract

1. 1. Fatty acid composition of liver phospholipids of warm and cold adapted freshwater fishes, differing in feeding habit ( Cyprinus carpio, omnivorous; Hypophatalmithryx molitrix, phytoplankton feeder; Aristichtis nobilis, zooplankton feeder: Ctenophyryngodon idella, feeding higher plants and Esox lucius, carnivorous) were investigated. All the fishes accumulated higher amounts of long chain polyunsaturated fatty acids, to the cost of saturated fatty acids, when adapted to cold. 2. 2. Liver slices prelabeled with [1- 14C]palmitic acid at 22°C liberate label in the free fatty acid fraction when exposed to 5°C in the absence of label in the incubation medium. This was not seen when [1- 14C]arachidonic acid was used as a label. Cycloheximide counteracted the cold induced activation of phospholipase A. 3. 3. There is an increase in the level of oleic acid at the cost of stearic acid in position 1 of phosphatidylethanolamines and in some cases of phosphatidylcholines in livers of cold-adapted fish. Marine fish collected from North Atlantic water ( Clupea harengus) showed the same level as those inhabiting tropic seas ( Sardinella longiceps). 4. 4. Liver slices of carp preferred to direct [1- 14C]oleic-, versus [9- 3H]palmitic acid into the position 1 of phosphatidylethanolamines at 5°C. Cycloheximide counteracted the cold induced accumulation of oleci acid in phosphatidylethanolamines. 5. 5. The results are discussed in terms of reorganization of the molecular architecture of phosphatidylethanolamines in cold adapted fish.