Incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids in phospholipid classes in cultured rainbow trout (Salmo gairdneri) cells

Abstract

The incorporation and metabolism of various (n-3) and (n-6) polyunsaturated fatty acids supplemented to the culture medium was investigated in the rainbow trout cell line, RTG-2. The distribution, and the occurrence and relative extent of further desaturation and elongation of the incorporated acids was determined in individual phospholipid classes by analysis of the fatty acid compositions. RTG-2 cells exhibited Δ6 and Δ5 desaturase activities whereas Δ4 desaturase activity was almost totally absent. The percentage of precursor acids was greatest in the phosphatidic acid/cardiolipin fraction (PA/CL), suggesting a role for possibly PA in the initial incorporation of these acids into the phospholipid pool. The compositional data indicated that individual intermediates and products of the desaturation pathways were associated with specific phospholipid classes probably via mechanisms depending upon the specificities of the acylating enzymes. The composition of phosphatidylinositol (PI) and the tightly controlled mechanisms for generating/maintaining it are consistent with a role for this phospholipid in providing precursor fatty acid for eicosanoid synthesis.

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

“…The specific incorporation and retention of AA in PI in juvenile sea bream is in agreement with previous analytical studies in both marine (Bell et al 1983;Tocher and Sargent 1984) and freshwater fish tissues (Henderson and Tocher 1987), and incorporation studies including injection of turbot in vivo (Linares and Henderson 1991) and in vitro studies on plaice, Pleuronectes platessa, neutrophils (Tocher and Sargent 1986), rainbow trout, Oncorhynchus mykiss, astrocytes (Tocher and Sargent 1990a) and mixed brain cells , and various fish cell lines (Tocher 1990;Tocher and Dick 1990;Tocher and Mackinlay 1990). In mammals, AA is the precursor of a wide range of highly biologically active derivatives collectively termed eicosaniods (Smith 1989).…”

Lipid and fatty acid compositions of cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and halibut (Hippoglossus hippoglossus)

“…The percentage of ArA was the highest in phosphatidyleinositol. These results agreed well with those previously reported on dogfish, Scyliorhinus canicula, cod, Gadus morhua (Bell et al, 1983;Bell and Tocher, 1990) and rainbow trout, Salmo gairdneri (Tocher, 1993). The relatively constant phospholipid composition in fish tissue indicates that phospholipids play a key role in the maintenance of metabolic and structural function in fish (Sargent et al, 1989, Tocher et al, 2008.…”

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“…As above, this is consistent with these agents inhibiting the conversion of 18:2n-6 to 20:4n-6, as it has been shown in many fish cell cultures that PE is the major phospholipid class that incorporates the greatest proportion of 18:2n-6, whereas the greatest proportion of 20:4n-6 is always incorporated into PI (Tocher 1990;Tocher and Mackinley 1990;Tocher and Dick 1990). The metabolism of 18:3n-3 by desaturation/elongation was less affected by dichlorvos and formalin and this was reflected in little effect on the phospholipid class distribution.…”

“…The fatty acid composition of these phospholipid classes are enriched in 18:0 in fish tissues and cells (Tocher 1995) including rainbow trout cell cultures (Tocher et al 1988;Tocher 1990). The proportion of radioactivity incorporated into PS and PE in [1-14 C]18:0 labelled cultures was increased by treatment with both dichlorvos and formalin.…”