Recent advances in the research concerning chemical mediators of inflammatory and allergic reactions have implicated two profoundly active lipids, viz. platelet activating factor and members of the leukotriene family. These lipids have strikingly similar pharmacological actions and evidence suggest a close biochemical interaction between these substances. While there are assays for the LTs based on biological activity, RIA, UV and HPLC properties, there exists only biological assays for PAF. Detailed studies of AGEPC (acetyl glycerol ether phosphocholine) which has been described as the structure of PAF, have been hampered without a specific, sensitive method of analysis. Such analytical capability is important to more fully evaluate the physiological role for AGEPC in health and disease. We propose to develop physico-chemical methods of quantitative analysis of PAF, its lyso-analogs, alkyl-acyl diglyceride, and acyl, ether phosphatidylcholine based on fast atom bombardment mass spectrometry and GC/MS using stable isotope techniques. These techniques will add to the existing analytical armamentorium to investigate each intermediate in our proposed acetyl ether PC cycle. This cycle is postulated to operate in certain cells leading to the synthesis of prostanoids, leukotrienes and/or PAF upon biological stimulation. We propose to investigate in detail precursor-product relationships between 1-0-hexadecyl-2-arachidonyl-glycerophosphocholine and eicosanoids using stable isotope and radioisotope tracer techniques. The metabolism of PAF, lyso PAF and 1-0-hexadecyl-2-arachidonyl-GPC will be carried out in cells including polymorphonuclear leukocytes, macrophages, monocytes and pulmonary endothelial cells. Basic information as to the turnover of arachidonic acid-containing lipids will be obtained in the cells under study. Furthermore, it is anticipated that potential pools for prostanoids and lipoxygenase products will be identified. Finally, various inhibitors of the biosynthesis of prostaglandins, leukotrienes and phospholipids will be employed to study the biochemical interrelationships between mediator synthesis. It is by understanding the specific biochemical events surrounding PAF and leukotrienes that development of specific pharmacologic agents, antagonists to these mediators, may be possible.
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