Ghioni C, Tocher D R, Bell M V, Dick J R, Sargent J R
Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK.
Biochim Biophys Acta. 1999 Feb 25;1437(2):170-81. doi: 10.1016/s1388-1981(99)00010-4.
The TF cell line, derived from a top predatory, carnivorous marine teleost, the turbot (Scophthalmus maximus), is known to have a limited conversion of C18 to C20 polyunsaturated fatty acids (PUFA). To illuminate the underlying processes, we studied the conversions of stearidonic acid, 18:4(n-3), and its elongation product, 20:4(n-3), in TF cells and also in a cell line, AS, derived from Atlantic salmon (Salmo salar), by adding unlabelled (25 microM), U-14C (1 microM) or deuterated (d5; 25 microM) fatty acids. Stearidonic acid, 18:4(n-3), was metabolised to 20:5(n-3) in both cells lines, but more so in AS than in TF cells. Delta5 desaturation was more active in TF cells than in AS cells, whereas C18 to C20 elongation was much reduced in TF as compared to AS cells. Only small amounts of docosahexaenoic acid (22:6(n-3)) were produced by both cell lines, although there was significant production of 22:5(n-3) in both cultures, especially when 20:4(n-3) was supplemented. We conclude that limited elongation of C18 to C20 fatty acids rather than limited fatty acyl Delta5 desaturation accounts for the limited rate of conversion of 18:3(n-3) to 20:5(n-3) in the turbot cell line, as compared to the Atlantic salmon cell line. The results can account for the known differences in conversions of C18 to C20 PUFA by the turbot and the Atlantic salmon in vivo.
TF细胞系源自一种顶级掠食性肉食性海洋硬骨鱼——大菱鲆（Scophthalmus maximus），已知其将C18多不饱和脂肪酸（PUFA）转化为C20多不饱和脂肪酸的能力有限。为了阐明潜在机制，我们通过添加未标记的（25微摩尔）、U-14C标记的（1微摩尔）或氘代的（d5；25微摩尔）脂肪酸，研究了硬脂酸（18:4(n-3)）及其延长产物20:4(n-3)在TF细胞以及源自大西洋鲑（Salmo salar）的AS细胞系中的转化情况。在这两种细胞系中，硬脂酸（18:4(n-3)）均被代谢为20:5(n-3)，但在AS细胞中的代谢程度高于TF细胞。Δ5去饱和在TF细胞中比在AS细胞中更活跃，而与AS细胞相比，TF细胞中C18到C20的延长则大大减少。尽管两种培养物中均有大量22:5(n-3)生成，尤其是在补充20:4(n-3)时，但两种细胞系产生的二十二碳六烯酸（22:6(n-3)）都很少。我们得出结论，与大西洋鲑细胞系相比，大菱鲆细胞系中18:3(n-3)向20:5(n-3)转化速率有限的原因是C18到C20脂肪酸的延长受限，而非脂肪酰基Δ5去饱和受限。这些结果可以解释大菱鲆和大西洋鲑在体内C18到C20 PUFA转化方面已知的差异。
