Modulation of prostaglandin synthesis in rat peritoneal macrophages with ω-3 fatty acids

In view of the findings that ω3 fatty acids inhibit the synthesis of prostaglandins (PG) from arachidonic acid (20∶4ω6) and that among immunologically active cells, the macrophage, is a major producer of PG, we undertook a study of the effect of dietary α-linolenic acid (18∶3ω3) on PG synthesis in the macrophage. Rats were fed purified diets containing either 10% corn oil (CO) or linseed oil (LO), providing either a low (1/32) or high (3.5/1) ratio of 18∶3ω3 to 18∶2ω6, respectively, for 6 weeks. Fatty acid analysis of macrophage phospholipids showed that there was an appreciable increase in the percentage of ω3 fatty acids and a decrease in the ω6 fatty acids in macrophages from rats fed the LO diet. The changes in fatty acid composition were associated with a significant decrease in the synthesis of prostaglandin E (PGE) by macrophages from rats fed the LO diet. Macrophages from rats fed the 2 dietary, oils did not differ in their ability to degrade PG, thus the difference in PG production appeared to be a consequence of decreased synthesis only. The dietarily induced changes in PGE synthesis were readily overcome in vitro by culturing macrophages with complexes of fat-free bovine serum albumin and either 20∶4ω6 or 20∶5ω3. Part of a dissertation submitted by Linda J. Magrum in partial fulfillment of the requirements for the Ph.D. degree in Nutritional Sciences. Honored Student Presentation at the AOCS 74th Annual Meeting, Chicago, 1983.