Fatty acid dynamics in phospholipids and incorporation of radio-labelled fatty acids into phospholipid fractions were examined, using granulation tissue induced by the implantation of formalin-soaked filter paper in rats. The effects of anti-inflammatory drugs on lipid dynamics were also studied. Concomitant with the progress of granulomatous inflammation, an increase in polyunsaturated fatty acids (mainly 20:4 (ω-6)) content of phospholipids was observed. Differing from saturated fatty acids, labelled polyunsaturated fatty acids (20:3 (ω-6), 20:4 (ω-6) and 20:5 (ω-3)) were easily incorporated in vivo into phosphatidylinositol and phosphatidylethanolamine in addition to phosphatidylcholine of granulation tissue. Indomethacin, tenoxicam and dexamethasone administered p. o. inhibited the granuloma formation. Indomethacin and tenoxicam had no marked effect on the tissue lipid composition. However, in dexamethasonetreated rats, tissue lipids were almost exclusively composed of triglycerides. Indomethacin and tenoxicam slightly decreased the percentages of 18:2 (ω-6) and 20:4 (ω-6) in phospholipid fractions.
Thus, polyunsaturated fatty acids released by lipolysis from fat cells accumulated in local inflammatory tissue in the early stage may be transferred into membrane phospholipids of inflammatory cells of later stage of inflammation and influence their functions. Antiinflammatory drugs may cause functional changes in cells accumulated in granulation tissue by changing the fatty acid components of the phospholipids.