DIETARY FISH OIL MODULATION OF INVIVO PERITONEAL MACROPHAGE LEUKOTRIENE PRODUCTION AND PHAGOCYTOSIS

Dietary fish oils (FO) are generally considered to have anti-inflammatory properties, due in part to the competitive inhibition of macrophage arachidonic acid (20:4n-6) metabolism by n-3 fatty acids. To further determine how FO feeding may act to influence macrophage function, mice were fed complete diets containing either 9% by weight FO supplemented with 1% corn oil (CO) containing linoleic acid (18:2n-6), 10% CO, or 10% borage oil (BO) containing 18:2n-6 and gammalinolenic acid (18:3n-6). After 2 wks, an acute inflammatory episode was induced by injecting unopsonized zymosan into the peritoneal cavity 1 hr prior to sacrifice. Peritoneal exudates were subsequently analyzed for in vivo leukotriene E, production by combined solid phase extraction and reverse phase high performance liquid chromatography. In addition, phagocytosis of zymosan was determined by light and electron microscopy. Peritoneal exudates from CO and BO animals contained five times more LTE4 than FO exudates (BO, 37.5 +/- 5.3 and CO, 29.6 +/- 3.3 versus FO, 6.5 +/- 3.3 ng/mouse). The fraction of FO macrophages ingesting zymosan was 62.2% compared with 32.6% in BO- and 35.0% in CO-fed animals. The mean number of particles ingested per macrophage was also elevated in FO, 4.31 versus BO, 3.51 and CO, 3.57. These results indicate that dietary FO is capable of suppressing macrophage eicosanoid metabolism and enhancing zymosan phagocytosis in vivo.