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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 activating 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 (less than 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.

The combination of a consecutive double capillary column gas chromatographic system (Deans type) with a fully automatic injection device was developed to determine quantitatively the fatty acid fraction of serum extracts, without prior removal of the other lipids. A major difficulty arose through ghosting (memory), via reaction of methylating reagents with lipid deposits, mainly in the injection port. Use of diazomethane circumvented this, as the reagent was easily removed prior to analysis. The combination methyl iodide--potassium carbonate, convenient handling of which requires coinjection of methyl iodide, proved to be less than completely dependable. Dimethylformamide dimethylacetal is completely out of the question as a coinjectant. Lipid deposits in the injection port produced peak area drifts which could, however, be counteracted. The apparatus is capable of analyzing samples completely unattended for at least 20 hours (80 samples). It has been operated non-stop, day and night, for between 4 and 7 days with occasional reloading and servicing.