Phospholipids of the cone-rich chicken retina and its photoreceptor outer segment membranes

Abstract

The lipid compositions of the cone-rich chicken retina and its outer segment membranes have been determined. The whole retina contained 25.1% lipid by weight, 26.0% of which were neutral lipids. Isolated outer segments contained 31.5% lipid by weight, 24.1% of which were neutral lipids. Total cholesterol represented 37.3 and 91.6% of the neutral lipid fractions from whole retina and isolated outer segments, respectively. The major phospholipids of the whole retina and outer segment membranes were phosphatidylcholine and phosphatidylethanolamine which represent, respectively, 41.8 and 33.5% of the total phospholipid of the whole retina and 44.9 and 34.9% of the phospholipids of the outer segment membranes. Phosphatidylserine was present as only 3.9 and 1.7% of the total phospholipids of whole retina and outer segment membranes, respectively. Sphingomyelin was present in relatively high concentration (9.1%) in whole retinal phospholipids and was enriched (11.0%) in the isolated outer segment membrane phospholipids. Palmitic (16:0), stearic (18:0), oleic (18:1), arachidonic (20:4) and docosahexanoic (22:6) acids account for most (80%) of the fatty acid of whole retinal phospholipids. Concentrations of arachidonic and docosahexanoic acid were highest in the serine and ethanolamine phosphatides from whole retina. There was little enrichment of these acids in any of the phospholipids of the outer segment membranes; instead, they were very high in linoleic acid.