Competitive inhibitions in the metabolism of polyunsaturated fatty acids studied via the composition of phospholipids, triglycerides and cholesteryl esters of rat tissues

Male rats which had been kept on fat-free diet and which were deficient in essential fatty acids were divided into ten groups. All ten groups received 0.8% of calories of linolenate, and nine received one of three levels of either linoleate, γ-linolenate or arachidonate for a period of six days. The rats were sacrificed, the livers, kidneys and testes were extracted, and the phospholipids, triglycerides and cholesteryl esters were separated by thin-layer chromatography. The fatty acid composition of each was determined by gas-liquid chromatography. The inhibition of the metabolism of linolenic acid by linoleate, γ-linolenate and arachidonate was evidenced in all three lipid classes and in all tissues. The activities in suppressing linolenate metabolism were in the order 20:4 >18:3 >18:2.