Incorporation of ¹⁴C‐labelled polyunsaturated fatty acids by juvenile turbot, Scophthalmus maximus (L.) in vivo

Abstract

The ability of juvenile turbot, Scophthalmus maximus (L.), to elongate and desaturate various polyunsaturated fatty acids (PUFA) was examined in relation to their lipid composition. Triacylglycerols were the most abundant lipid class present in the fish and phosphatidylcholine was the predominant phospholipid. In all lipid classes examined the levels of (n-3) PUFA exceeded that of (n-6) PUFA. 18C PUFA were minor components in comparison with 20:5(n-3) and 226(n-3). 20:4(n-6) was present in highest concentration in phosphatidylinositol in which it accounted for 16.9% of the fatty acids. When the fish were injected with either i4C-labelled 18:2(n-6), 18:3(n-3), 20:4(n-6), 20:5(n-3) or 22:6(n-3) the highest percentage recovery of radioactivity (69%) in body lipid was observed with 22:6(n-3). With all labelled substrates free fatty acids contained only a small proportion of the total recovered radioactivity whereas triacylglycerols were highly labelled. Phosphatidylcholine/sphingomyelin was the most highly labelled polar lipid fraction. With W-20:4(n-6) as injected substrate, 23.2% of the radioactivity recovered in total lipid was present in phosphatidylinositol in comparison with less than 6% with the other substrates. Only small proportions of radioactivity from "CC-18:2(n-6) and '%-18:3(n-3) were recovered in the 20 and 22C fatty acids of triacylglycerols and total polar lipid. With I4C-20:5(n-3) as substrate, 27 and 33% of the total radioactivity recovered in the fatty acids of triacylglycerols and polar lipids respectively was present in 22C fatty acids. The corresponding values for '%-204(n-6) as substrate were 19 and 18%. The results confirm the limited capacity of turbot to convert 18C PUFA to longer chain PUFA but demonstrate their ability to synthesize 22C PUFA from 20C PUFA. They also suggest a small but specific requirement for 20:4(n-6).

Arachidonic acid reduces the stress response of gilthead seabream Sparus aurata L.

“…ArA is deposited mainly into the polar lipids, especially at lower dietary levels. Hence, the increase in ArA concentration in kidney tissues apparently reflects changes in the polar lipid fraction, which are more rapid than in the neutral lipid pool (Linares and Henderson, 1991;Fountoulaki et al, 2003). Changes in the fatty acid composition of fish muscle, on the other hand, are thought to result from a dilution effect on neutral lipid pools.…”

“…ArA is selectively incorporated into cellular phospholipids, especially phosphatidylinositol, despite the general abundance of n-3 PUFA in phospholipids of fish tissues (Linares and Henderson, 1991). While the structural contribution of ArA to the membrane appears to be limited, ArA can be rapidly converted into eicosanoids, which can function as endocrine, paracrine and/or autocrine modulators of secretory mechanisms in various organs (Bihoreau et al, 1990;Lands, 1991).…”

Incorporation and metabolism of 14C-labelled polyunsaturated fatty acids in juvenile gilthead sea bream Sparus aurata L. in vivo

“…It was previously established that radioactive fatty acids (3-5 1zCi), dissolved in a small volume of ethanol (5-20 1lA) can be injected into the intraperitoneal cavity of anaesthetized fish without apparent detrimental effects, yielding sufficient levels of radioactivity in the body lipids to permit subsequent analyses (Linares and Henderson 1991;Olsen and Ringo 1992). In the present study, six groups of three fish were starved for one week prior to injection to ensure no dietary input of C 20 and C 22 PUFA and to maximize the rate of bioconversion of the injected 1 4 C-labelled PUFA.…”

Fatty Acids Profile and Cholesterol Contents of Three Brazilian Brycon Freshwater Fishes

“…Freshwater "shes are also of interest because they seem to have a greater capacity than marine "shes to elongate and desaturate the shorter FA, synthesized by algae or plants, into the longer EPA and DHA (Bell et al, 1986;Henderson and Tocher, 1987;Linares and Henderson, 1991), to convert food of lower nutritional value into food of higher nutritional value.…”