Ether lipid content and fatty acid distribution in rabbit polymorphonuclear neutrophil phospholipids

This study was undertaken to determine if rabbit neutrophils contain sufficient ether‐linked precursor for the synthesis of 1‐ O ‐alkyl‐2‐acetyl‐ sn ‐glycero‐3‐phosphocholine (platelet activatin factor) by a deacylation‐reacylation pathway. The phospholipids from rabbit peritoneal polymorphonuclear neutrophils were purified and quantitated, and the choline‐containing and ethanolamine‐containing phosphoglycerides were analyzed for ether lipid content. Choline‐containing phosphoglycerides (37%), ethanolamine‐containing phosphoglycerides (30%), and sphingomyelin (28%) were the predominant phospholipid classes, with smaller amounts of phosphatidylserine (5%) and phosphatidylinositol (<1%). The choline‐linked fraction contained high amounts of 1‐ O ‐alkyl‐2‐acyl‐(46%) and 1,2‐diacyl‐ sn ‐glycero‐3‐phosphocholine (54%), with a trace of the 1‐ O ‐alk‐1′‐enyl‐2‐acyl species. The ethanolamine‐linked fraction contained high amounts of 1‐ O ‐alk‐1′‐enyl‐2‐acyl‐(63%) and 1,2‐diacyl‐ sn ‐glycero‐3‐phosphoethanolamine (34%), and a low quantity of the 1‐ O ‐alkyl‐2‐acyl species (3%). The predominant 1‐ O ‐alkyl ether chains found in the sn ‐1 position of the choline‐linked fraction were 16∶0 (35%), 18∶0 (14%), 18∶1 (26%), 20∶0 (16%), and 22∶0 (9%). The major 1‐ O ‐alk‐1′‐enyl ether chains found in the sn ‐1 position of the ethanolamine‐linked fraction were 14∶0 (13%), 16∶0 (44%), 18∶0 (27%), 18∶1 (12%) and 18∶2 (3%). The major acyl groups in the sn ‐1 position of 1,2‐diacyl‐ sn ‐glycero‐3‐phosphocholine and 1,2‐diacyl‐ sn ‐glycero‐3‐phosphoethanolamine were 16∶0, 18∶0 and 18∶1. The most abundant acyl group in the sn ‐2 position of all classes of choline‐ and ethanolamine‐linked phosphoglycerides was 18⩺2. Although this work does not define the biosynthetic pathway for platelet activating factor, it does show that there is ample precursor present to support its synthesis by a deacylation‐reacylation pathway.