Comparative studies on lipid metabolism in various salt transporting organs of the European eel (Anguilla anguilla). Mono-unsaturated phosphatidylethanolamine as a key substance

Abstract

1. Incorporation in vivo into tissue lipids of (1-14C)acetate added to the water in the incubation tank showed the same relative distribution pattern of 14C-activity among various phospholipids in the gills, the esophagus and the intestine, when the eel was incubated in sea-water; in fresh water this pattern was found only in the intestine, while both the gills and the esophagus showed a relative excess of 14C-label in phosphatidylethanolamine (PE). 2. Similar studies with (32P)phosphate also showed a relative excess of (32P)PE in both the gills and esophagus in fresh water compared to sea-water, and no such difference in the intestine. 3. As long as the labelled precursors were added to the water in the incubation tank both (14C)PE and (32P)PE were not identical to unlabelled PE on thin-layer chromatograms, and the 14C-labelled lipids contained predominantly C16:1 and C18:1 fatty acids. 4. However, when the two precursors were injected directly into the eel there was no longer any marked difference between the distribution patterns of radioactivity among gill phospholipids in fresh water and sea-water; there was no longer any difference between labelled and unlabelled PE on thin-layer chromatograms, and the 14C-labelled gill lipids contained predominantly C16:0 and C18:0 fatty acids. 5. The corresponding liver lipids were affected neither by a change in environmental salinity nor in precursor application.