Suppression of arachidonic acid in lipids of rat tissues by dietary mixed isomeric cis and trans octadecenoates.

The influence of dietary isomeric cis and trans octadecenoic fatty acids (ICTO) on the metabolism of polyunsaturated fatty acids in rat tissues was studied by feeding a defined diet rich in partially hydrogenated soybean oil. Experimental and control animals received equal and more than adequate amounts of linoleic and linolenic acids. The total phospholipid (PL) fatty acids of liver, heart, testis, brain and sciatic nerve, and the fatty acids of liver triacylglyceride, cholesteryl ester and individual PL classes were analyzed by capillary gas chromatography. The content of arachidonic acid in the total fatty acids of liver lipids of ICTO-fed rats was found to be lower than those from control rats by the following amounts (in percent): total PL, 35; phosphatidylcholine, 50; phosphatidylinositol, 35; phosphatidylserine 26; phosphatidylethanolamine, 12; cholesteryl ester, 55; and tryglyceride 75. PL 18:2 omega 6 and 20:3 omega 6 levels were elevated, suggesting inhibition of the desaturase-elongase enzymes involved in synthesis of arachidonic acid. Synthesis of 20:5 omega 3 and 20:3 omega 9 was accentuated by the ICTO diet, suggesting an omega 6 series-specific inhibition. A nearly perfect negative correlation between cis 12-18:1 and arachidonic acid was found in liver PL.