EFFECT OF DIETARY N-9 EICOSATRIENOIC ACID ON THE FATTY-ACID COMPOSITION OF PLASMA-LIPID FRACTIONS AND TISSUE PHOSPHOLIPIDS

n-9 Eicosatrienoic acid (ETrA), also known as Mead acid, is a minor fa tty acid in essential fatty acid (EFA)-sufficient healthy subjects but is found at increased levels in EFA deficiency. This study examined t he influence of dietary ETrA from a biological source on plasma and ti ssue ETrA. A synthetic fat-free diet was prepared to which was added M ut 48 oil which contains 19% ETrA (wt%) as well as other n-9 fatty aci ds. Blends of vegetable oils were used to achieve overall diets with 5 % fat (wt%) and varying amounts of ETrA at two different dietary level s of linoleic acid (LA), approximately 4.4 and 19% of total fatty acid s. These diets were fed to 5-week-old Dark Agouti rats for four weeks. Plasma lipid fractions and liver, spleen, and peritoneal exudate (PE) cells were analyzed for fatty acid composition. ETrA was present at u p to 20% total fatty acids in plasma triglyceride, cholesterol ester, and phospholipid fractions. ETrA also accumulated to substantial level s in phospholipids of liver and spleen (up to 15% of total fatty acids ) and PE cells (up to 11%). ETrA was found in plasma and tissue phosph olipids in proportion to the amount of ETrA present in the diet. The i ncorporation was reduced in diets with higher LA content compared to d iets containing similar amounts of ETrA but lower LA. All rats remaine d apparently healthy, and histological survey of major organs revealed no abnormality. While the long-term implications for health of ingest ion of diets rich in ETrA remain to be established, rats appear to tol erate high levels of dietary ETrA without adverse effects. Dietary enr ichment with ETrA warrants further investigation for possible benefici al effects in models of inflammation and autoimmunity, as well as in o ther conditions in which mediators derived from n-6 fatty acids can af fect homeostasis adversely.