Characterization of the total lipid and fatty acid composition of rat olfactory mucosa

Phospholipid accounted for 81% (by weight) of the total lipid of rat olfactory mucosa. Phosphatidylcholine (46% of total phospholipids) and phosphatidylethanolamine (26%) were the predominant phospholipids. Phosphatidylinositol (8%), sphingomyelin (6%), and phosphatidylserine (7%) were the next most abundant phospholipids, with cardiolipin (4%) and phosphatidic acid (1%) present in lesser amounts. Only trace amounts of the polyphosphoinositides, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate were detected. Sterol was the major neutral lipid present (83% of the total neutral lipid mass) with lesser amounts of triacylglycerols (7%), steryl esters (6%), free fatty acids (4%), and diacylglycerols (1%). Monoacylglycerols were detected only in trace amounts. The sterol to phospholipid ratio was 0.39:1. Most of the phospholipids of the olfactory mucosa showed a high polyunsaturated fatty acid content, with the arachidonic acid (20:4) and docosahexaenoic acid (22:6) residues predominating. The fatty acids in sphingomyelin, however, were almost totally saturated and included the 24:0 and 24:1 residues, which were not detected in other phospholipids. Polyunsaturated fatty acids accounted for less than 25% of the total fatty acid of any individual neutral lipid and comprised largely linoleic and arachidonic acids. The results are discussed in relation to the putative role of lipids in olfactory signal transduction.