The comparative effects of dietary alpha-linolenic acid and fish oil on 4- and 5-series leukotriene formation in vivo.

The comparative effects of dietary alpha-linolenic acid and fish oil on eicosanoid metabolism was studied in vivo. Resident murine peritoneal cells were stimulated in vivo with opsonized zymosan in animals maintained on diets containing increasing amounts of alpha-linolenic acid or fish oil concentrate with projected n-3/n-6 ratios of 0.2, 0.4 and 1.0. While fish oil feeding resulted in significant changes in eicosapentaenoate tissue levels, alpha-linolenic acid was preferentially metabolized to docosahexaenoate. High performance liquid chromatographic analysis revealed the formation of leukotriene E5 (LTE5) in all the fish oil groups (19.8 +/- 3.5 ng/mouse to 83.3 +/- 13 ng/mouse), but only in the highest linolenic acid group (6.0 +/- 3.2 ng/mouse). Concomitantly, the 4-series sulfidopeptide leukotrienes and PGI2 were significantly reduced in the two highest fish oil containing dietary groups. Similar reductions were observed in the highest linolenic acid group, but the changes were not statistically different from the control values. In summary, this paper reports the de novo synthesis of 5-series sulfidopeptide leukotrienes in animals consuming alpha-linolenic acid. It also reveals that dietary fish oil is 2.5 to 5 times more effective than alpha-linolenic acid in modulating eicosanoid metabolism and altering tissue phospholipid fatty acid composition.