Dietary long-chain polyunsaturated fatty acids influence tissue fatty acid composition in rats at weaning.

We studied the fatty acid composition of plasma, plasma phospholipids, erythrocyte membrane lipids, liver microsomal phospholipids and brain lipids in rats fed three different diets varying in their (n-3) and (n-6) long-chain polyunsaturated fatty acid (LCP) concentrations for 0, 2 and 4 wk after weaning. The three diets contained 10% fat; diet HO had a high-oleic acid proportion; diet FO was enriched in n-3 LCP provided by fish oil; and diet FO + BPL contained n-3 and n-6 LCP supplied by fish oil and a brain phospholipid concentrate. At 2 and 4 wk after weaning the proportions of oleic acid in all tissues, except in liver microsomes of the FO + BPL group, were significantly higher than in weanling rats. The absence of (n-3) LCP intake resulted in significantly lower levels of docosapentaenoic [20:5(n-3)] and 22:6(n-3) acids in plasma, plasma phospholipids, erythrocyte membrane lipids and liver microsomal phospholipids but not in brain lipids compared with rats at weaning. Dietary supplementation with (n-3) LCP (FO and FO + BPL groups) for 4 wk led to higher levels of 22:6(n-3) in all tissues compared with rats fed the HO fat. The proportions of 20:4(n-6) and total (n-6) LCP were significantly lower in all tissues from rats fed the FO diet than in rats at weaning and rats fed the HO diet. After 2 and 4 wk, rats fed the FO + BPL diet had significantly higher levels of 20:4(n-6) and total (n-6) LCP in plasma, plasma phospholipids, erythrocyte lipids and liver microsomal phospholipids; the brain also showed a higher content of those fatty acids after 4 wk. Our results suggest that dietary supplementation with 20:4(n-6) and 22:6(n-3) influences the concentration of 20:4-(n-6) and 22:6(n-3) in body tissues of rats after weaning.