Tissue culture of cocoa bean (Theobroma cacao L.): Incorporation of fatty acids into lipids of cultured cells

Suspension cell cultures of cocoa bean rapidly incorporated palmitic, stearic, oleic and linoleic acids into cellular lipids. Thus, 75 and 20% of [1-¹⁴C] palmitic acid was incorporated into polar lipids and triglycerides, respectively, after 48 hr. When [1-¹⁴C] oleic and [1-¹⁴C] linoleic acid were added separately, polar lipids consistently contained most of the radioactive fatty acids. Ca. 60% of the stearic acid accumulated as unesterified fatty acid in the cells. Palmitic and stearic acid were not desaturated, but oleic acid and linoleic acid were further desaturated. The kinetics of conversion of oleic acid and linoleic acid suggested a sequential desaturation pathway of 18∶1→18∶2→18∶3 in cocoa bean cell suspensions.     

Oxidative desaturation of α-linolenic,linoleic, and stearic acids by human liver microsomes

The desaturation of stearic, linoleic, and α-linolenic acids by human liver microsomes were studied. The microsomes were isolated from liver biopsies obtained during operations. It was shown that human liver microsomes are able to desaturate 1-¹⁴C-α-linolenic acid to octadeca-6,9,12,15-tetraenoic acid; 1-¹⁴C-linoleic acid to γ-linolenic acid; and 1-¹⁴C-stearic acid to oleic acid in the same system described in the rat. However, the desaturation activity obtained was low compared to other mammals. This effect was attributed to fasting, premedication, or the anaesthesia.     

Lipid products formed during desaturation of [1-14C] stearyl CoA by hen liver microsomes

A number of lipid products are formed during the desaturation of stearyl CoA by hen liver microsomes. This article presents an analysis of the products formed when [1-¹⁴C] stearyl CoA is incubated with hen liver microsomes for various time periods. [1-¹⁴C] Oleyl CoA was the first radioactive unsaturated product formed. Synthesis of phospholipids containing [1-¹⁴C] oleic acid occurs only after the desaturase activity has begun to decline. The specific radioactivity of [1-¹⁴C] oleyl CoA was similar to the specific radioactivity of [1-¹⁴C] stearyl CoA at all time periods tested. The specific radioactivities of [1-¹⁴C] oleic acid and phospholipids containing [1-¹⁴C] oleic acid were much lower than that of the [1-¹⁴C] stearyl CoA.     

The absorption of fatty acids by functional bovine mammary cells

Freshly dispersed bovine mammary cells rapidly absorbed long chain fatty acids from the culture medium. Differences in the rates of absorption were observed, i.e., palmitic > stearic > oleic > myristic > linoleic acid. The preponderance of the fatty acids absorbed were esterified into triglycerides (>75%) and the remainder were mostly incorporated into phospholipids. The cells secreted triglycerides into the culture medium. Of the phospholipid classes, phosphatidylcholine always contained most of the radioactivity in all experiments with labeled fatty acids. These observations are related to the metabolism of mammary cells in vivo.     

Tissue culture of cocoa beans (Theobroma cacao L.): Incorporation of acetate and laurate into lipids of cultured cells

Suspension cultures of cocoa bean tissue readily incorporated exogenous acetate into lipids. The distribution of radioactivity from acetate in individual lipid classes after 48 hr was 20, 5, 1, 15, 25, and 35% in triglycerides, diglycerides, free fatty acids, sterol esters, sterols and polar lipids, respectively. The labeled acetate was rapidly incorporated into various fatty acids within 2 hr. The [1-¹⁴C] saturated fatty acids declined slightly after 4 hr, whereas [1-¹⁴C] oleate declined significantly after 2 hr. There was a concomitant increase in [1-¹⁴C] linoleate. The radioactivity associated with linolenate was relatively high up to 4 hr, declined by 24 hr, and then increased again. The kinetics of fatty acid labeling suggested that biosynthesis of linolenic acid in cocoa bean suspension culture may occur via the desaturation of linoleic acid and the chain elongation of dodecatrienoic acid. The patterns of fatty acid radiolabeling following incubation of cells with [1-¹⁴C] laurate was consistent with this mechanism.     

Fatty acid biosynthesis and incorporation into lipid classes in seeds and seed tissues of flax

Fatty acid metabolism in developing flaxseeds was studied by incubating whole seeds or isolated seed tissues in buffered solutions of 1-¹⁴C-acetate, 2-¹⁴C-malonate and¹⁴CO₂. Lipid classes were separated by thin layer chromatography, and fatty acid labeling in phospholipids, diglycerides and triglycerides was determined by combined thin layer and gas liquid chromatographic techniques. Incorporation of¹⁴C from acetate into embryo lipids was very rapid with phospholipids and 1,2-diglycerides becoming highly labeled in treatment times as short as 5 min. Triglycerides were labeled more slowly. Phospholipid radioactivity was largely associated with the phosphatidyl choline fraction. Oleic acid had the highest specific activity of all major fatty acids in short treatment periods. This was followed in decreasing order of activity by palmitic, linoleic, stearic and linolenic acids. As the treatment period was lengthened to 90 min or longer, linoleic and linolenic activities were markedly increased. Use of malonate or CO₂ rather than acetate as the substrate increased the labeling of the saturated acids. Incorporation of¹⁴C from acetate into lipids of endosperm tissues and whole flax seeds was slower than incorporation into embryo lipids. Stearate had the highest specific activity of the fatty acids in endosperm and whole seeds. Presented in part at the AOCS Meeting in New York, October 1968.     

Polyenoic acid metabolism in cultured human skin fibroblasts

The incorporation of [1-¹⁴C]linoleic acid, and [1-¹⁴C]linoleic acid into cellular lipids of cultured human skin fibroblasts was studied. Cultured cells took up both labeled fatty acids at nearly the same rate and incorporated them into a variety of lipid classes. At the end of 1 hr incubation with [1-¹⁴C]linoleic acid, radioactivity was found in the triacylglycerol (TG) and choline phosphoglyceride (CPG) pools preferentially. Incorporation into the TG fraction decreased rapidly, while the uptake into CPG, serine phosphoglyceride (SPG), and ethanolamine phosphoglyceride (EPG) fractions increased progressively with longer incubation times. Similar results were obtained with [1-¹⁴C]linoleic acid as precursor. At the end of 24 hr, desaturation and chain elongation of 18∶3 n−3 was more extensive than conversion of 18∶2 n−6 to higher polyenoic acids. During pulse-chase experiments with either fatty acid precursor, the incorporated radioactivity was progressively lost from cellular lipids, particularly from the TG and CPG fractions, but continued to increase in the SPG and EPG pools. The similar labeling pattern of cellular phospholipids with linoleic or linolenic acids, and data from pulse-chase studies suggest that a direct transfer of fatty acids from CPG to EPG is a likely pathway in fibroblast cultures. Incorporation into the EPG pool during the pulse-chase experiments paralleled extensive desaturation and elongation of linoleic acid into 20∶4 n−6, and 22∶4 n−6; and of linolenic acid into 22∶5 n−3 and 22∶6 n−3.     

The biosynthesis of polyunsaturated fatty acids in plants

This paper is a review of some of the work being done at the author's laboratory. The phospholipids and glycolipids of the alga,Chlorella vulgaris, have been implicated in fatty acid transformations such as chain elongation and desaturation. Labeling studies with [¹⁴C] acetate have shown that newly synthesized galactosyl glycerides have mainly saturated fatty acids. Subsequent to de novo synthesis, a series of alterations of fatty acid structure takes place within the same glycolipid molecules. The specific incorporation of [¹⁴C] oleic acid intoChlorella phosphatidyl choline provides a convenient model system for studying the lipid dependent desaturation of oleic to linoleic acid. The inhibitor of fatty acid desaturation, sterculic acid, only inhibits the conversion of oleate into linoleate if added before the precursor fatty acid has been incorporated into a complex lipid. Studies with isomeric monoenoic fatty acids have suggested that there are two enzymes which catalyze the formation of linoleic from oleic acid. One measures the position of the second double bond from the carboxyl group, the other, from the methyl end of the chain. The latter enzyme probably requires the complex lipid substrate.     

Early steps on the in vivo incorporation of 1-14C-linoleic acid into liver lipids from normal and essential fatty acid deficient rats

Essential fatty acid (EFA) deficient rats were injected intraportally with a solution of 1-¹⁴C-linoleic acid during a 1 min period. Livers were quickly frozen, pulverized, and the lipids extracted and fractioned by thin layer chromatography. The incorporation of 1-¹⁴C-linoleic acid into liver lipids was measured. The results were compared with those previously obtained from normal rats. No significant differences were observed in the total radioactivity recovered from lipid extracts. While the distribution of radioactivity into the 1–2 diacylglycerol fraction remained unchanged in both groups of rats, in the EFA deficient rats the 1-¹⁴C-linoleic acid incorporation was actually directed to the phospholipid fractions instead of to the triacylglycerol fractions as was observed in the normal rats.     

Lipids of cultured hepatoma cells: VI. Glycerolipid and monoenoic fatty acid biosynthesis in minimal deviation hepatoma 7288C

1-14C-Acetic, 1-14C-palmitic, or 1-14C-stearic acid was incubated with minimal deviation hepatoma 7288C cells grown in culture to assess: de novo fatty acid synthesis, oxidation, desaturation, and elongation of saturated fatty acids, as well as the ability of media fatty acids to serve as precursors of cellular glycerolipids. Distribution of radioactivity in the individual lipid classes and the various fatty acids of triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine was determined. The radioactivity among the monoenoic acid isomers derived from triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine was analyzed by reductive ozonolysis. Only small amounts of the labeled substrates were oxidized to carbon dioxide. Except for labeled stearic acid, which also was incorporated heavily into phosphatidyl inositol and phosphatidyl serine, most radioactivity was recovered in triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine. Synthesis of cholesterol and long chain fatty acids from labeled acetic acid demonstrated that these cells can perform de novo synthesis of fatty acids and cholesterol. Both labeled palmitic and stearic acids were desaturated to the corresponding delta9 monoenes, and palmitic and palmitoleic acids were elongated. The nexadecenoic acid fraction isolated from triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine, when acetic or palmitic acid was the labeled substrate, showed that greater than 70 percent of the labeled acids were the delta9 isomer. Radioactivity of the octadecenoic acid fraction derived from labeled acetic or palmitic acids was nearly equally divided between the delta9 isomer, oleic acid, and the delta11 isomer, vaccenic acid. Desaturation of labeled stearic acid produced only oleic acid. These data demonstrate that the biosynthesis of vaccenic acid in these cultured neoplastic cells proceeds via the elongation of palmitoleic acid. The relatively high level of vaccenic acid synthesis in these cells suggests that the reported elevation of "oleic acid" in many neoplasms may result from increased concentration of vaccenic acid.     

Incorporation of [1-14C] acetate into lipids of soybean cell suspensions

Suspension cultures of soybean cells incorporated [1-¹⁴C] acetate very rapidly into the fatty acid moieties of phospholipids and glycolipids when incubated at 26 C for up to 22 hr. The most rapidly labeled lipid was 3-sn-phosphatidylcholine, which contained 58% of the total fatty acid radioactivity after 16 min; more than 75% of this label was found to be in the oleic acid of the phosphatidylcholine. After longer periods of incubation, the proportion of¹⁴C label decreased exponentially in phosphatidylcholine and increased markedly in an unidentified phospholipid (tentatively,bis-phosphatidic acid), di- and triacylglycerols, and glycolipids. The proportion of radioactivity in oleic acid also decreased exponentially, accompanied by increases in linoleic acid first and then in linolenic acid. Most of the labeled linolenic acid at 22 hr was found in the unidentified phospholipid, di- and triacylglycerols, and the glycolipid fraction. Contribution no. 537, Ottawa Research Station, Agriculture Canada. A preliminary report was presented at the 20th International Conference on the Biochemistry of Lipids at Aberdeen, Scotland, September 1977.     

Positional specificity oftrans fatty acids in fetal lecithin

Differences in the positional incorporation of 9-trans[1-¹⁴C] octadecenoic (elaidic) and 9-trans,12-trans[1-¹⁴C] octadecadienoic (linoelaidic) acids in fetal lecithin of rats were demonstrated. On the 20th day of gestation, a¹⁴C-labeled albumin complex of elaidic or linoelaidic acid was injected into the jugular vein of pregnant rats. For comparative purposes, 9-cis[1-¹⁴C] octadecenoic (oleic) or 9-cis,12-cis[1-¹⁴C] octadecadienoic (linoleic acid) was injected into the maternal circulation of rats. Animals were killed 6 hr later. Distribution of label in total lipids and phospholipids (PL) of fetal tissue was measured by TLC. Irrespective of the label, the highest percentage of total radioactivity was associated with PL-59 to 67%. Within PL, the major portion of radioactivity was found in choline phosphoglycerides (CPG)-53 to 67%, and in ethanolamine phosphoglycerides (EPG)-18 to 33%. While linoelaidic acid was predominantly esterified in the 2-position of CPG, elaidic acid was nearly equally distributed between positions 1 and 2 of lecithin. Distribution of radioactivity within fatty acid methyl esters (FAME) of CPG measured by radio-GLC suggested that oleic and possibly linoleic acids may be converted to nervonic and arachidonic acid, respectively, in the rat by the 20th day of gestation. Following injection of elaidate, radioactivity of FAME was distributed between palmitate and elaidic acid indicating that rat fetal tissue may metabolize elaidic acid via β-oxidation. In contrast, following injection of linoelaidate, radioactivity of FAME was primarily associated withtt-18∶2, suggesting little biotransformation to other fatty acids by fetal tissues.     

Lipids of cultured hepatoma cells: III. Triglyceride and phosphoglyceride biosynthesis in minimal deviation hepatoma 7288C

Minimal deviation hepatoma 7288 C cells were cultured on media containing 25% serum to the confluent stage. The growth media was replaced with serumfree media containing 1-¹⁴C-palmitate, and incubations were continued for 0.75, 1.5, 3, 6, 12, and 24 hr. The distribution of radioactivity among the major neutral lipids and phosphoglycerides was determined for cells and culture media. Radioactivity in individual fatty acids of cellular triglyceride, phosphatidylcholine, and phosphatidylethanolamine also was determined. After 24 hr, more than 95% of the administered radioactivity was recovered in neutral and phosphoglycerides, indicating that only a small amount of the fatty acid was oxidized. At any time period examined, over 80% of the incorporated radioactivity was found in triglyceride, phosphatidylcholine, and phosphatidylethanolamine. Incorporation of the label into cellular triglyceride and phosphatidylcholine plateaued at 12 hr, whereas incorporation of radioactivity into phosphatidylethanolamine still was increasing at 24 hr. In contrast, during the entire incubation period the relative distribution of¹⁴C among esterified lipid classes in the culture media remained constant. Elongation of palmitic acid to stearic acid and its subsequent desaturation to oleic acid suggests that these cells possess an active elongation and monoenoic desaturation system. Labeled glycerol ether diesters were not detected in the cells or culture media. Positional distribution of the¹⁴C label in the triglyceride and phosphatidylcholine suggests that minimal deviation hepatoma cells do not exhibit diglyceride selectivity in the biosynthesis of these two lipid classes.     

Short term essential fatty acid deficiency in rats. Influence of dietary carbohydrates

The effects of long term (8–14 wk) essential fatty acid (EFA)-deprived diets in rats are well documented. In the present study, we compared, in weanling rats, the effect of a short term (two wk) hydrogenated coconut oil, EFA-deprived, diet (D) with that of a corn oil, EFA-adequate, diet (A), using either sucrose (SU) or starch (ST) as carbohydrate. After two wk, rats fed the sucrose/hydrogenated coconut oil diet developed some characteristic features of EFA deprivation: slower growth rate, decreases in linoleic and arachidonic acid of plasma phospholipids and an increase in n−9 eicosatrienoic acid of plasma phospholipids. When rats ate the starch/hydrogenated coconut oil diet, there was a similar decrease in linoleic acid of plasma phospholipids, but only a small effect on growth rate and no change in the arachidonic acid content of plasma phospholipids. EFA deprivation and sucrose had opposite effects on plasma triglyceride (TG) levels: deprivation induced a decrease, whereas the sucrose induced an increase in very low density lipoprotein (VLDL) triglycerides. The observed decrease in plasma triglyceride during EFA deporivation might result from an activation of lipoprotein lipase during the early stages of deprivation.     

Lipid metabolism in plasma,liver, and adipose tissue of rats with experimental chronic nephrotic syndrome

Plasma, liver, and adipose tissue lipid composition and synthesis from [1-¹⁴C] acetate were studied three months following induction of nephrotic syndrome in rats by injection of antiglomerular basement membrane protein. Plasma triglyceride concentrations and specific radioactivities were elevated, and the triglycerides contained increased proportions of oleic acid. Plasma cholesterol and phospholipid concentrations were also increased, but free fatty acid levels were not. Liver triglyceride concentrations were decreased and incorporation of [1-¹⁴] acetate into liver triglycerides was also depressed below that of normal controls. Nephrotic rat liver triglycerides contained a higher proportion of oleic acid and lower arachidonic acid than did controls. Incorporation of [1-¹⁴C] acetate into adipose tissue lipids of the nephrotic rats was increased, and the proportion of palmitic acid was decreased. In the chronic nephrotic rat, the major source of the increased plasma triglycerides may be fatty acids mobilized from adipose tissue stores.     

Circadian rhythm of fatty acid desaturation in mouse liver

A study was made of the diurnal changes in liver microsomal desaturation of labeled stearic, linoleic and α-linolenic acids to oleic, γ-linolenic and octadeca-6,9,12,15-tetraenoic acids, respectively. C3H-S mice were used and were exposed to light-dark cycles. A circadian rhythm was observed for stearic acid desaturation, and a different one for linoleic acid. Linoleic and α-linolenic desaturation had similar responses in the day cycle. This would indicate that different mechanisms control the oxidative desaturations of the fatty acids in the 9 and 6 carbons. The fatty acid composition of the whole liver and liver microsomes also showed variations. Remarkable oscillations were observed for stearic and oleic acids. Neither the total protein synthesis nor the free fatty acid concentration in the microsomes followed a rhythm parallel to the desaturation of the studied fatty acids. The injection of cycloheximide 4 hr before measuring the desaturation modified the circadian variation of both the 9 and 6 desaturations. The modification induced by cycloheximide was considered to indicate that both variations are related to the synthesis of specific proteins but not to that of a degradative or inhibitory protein.     

Effect of ATP on the microsomal desaturation of unsaturated fatty acids

The effect of ATP on the microsomal desaturation of linoleic acid to γ-linolenic acid was studied in a system in vitro with the following results: (1) preincubation of rat liver microsomes with ATP alone in N₂ or in the presence of CoA and Mg⁺⁺ followed by subsequent incubation with 1-¹⁴C-linoleic acid plus NADH in O₂ resulted in enhancement of 1-¹⁴C-linoleic acid desaturation when compared with control samples in which no preincubation was performed; (2) the preincubation of the microsomes with ATP, Mg⁺⁺ and CoA in the presence of 1-¹⁴C-linoleic acid decreased the desaturation of the labeled acid to γ-linolenic acid upon subsequent incubation with NADH, as a consequence of incorporation of the acid into the microsomal lipids; (3) the increase of linoleic acid desaturation depended on the ATP concentration during preincubation and followed a sigmoidal curve. It was specific for ATP, and neither GTP, CTP, ADP nor AMP produced a similar effec. However, GTP or CTP could replace ATP as a cofactor in the microsomal desaturation of free linoleic acid to γ-linolenic, suggesting that directly or indirectly they may activate conversion of the free acid to linoleyl-CoA; (4) preincubation of microsomes with ATP activated the acylation of CoA. However, this activation showed no quantitative correlation with enhancement of the desaturation reaction; (5) addition of ATP also stimulated conversion of linoleyl-CoA to γ-linolenic acid. This enhancement was not related to inhibition of the linoleyl-CoA hydrolase; (6) however, in spite of these results, preincubation with ATP did not increase the initial velocity of linoleic acid or linoleyl-CoA desaturation; (7) preincubation of microsomes with ATP also increased the 6-desaturation of oleic acid and α-linolenic acid but did not increase the 9-desaturation of plamitic and stearic acid.     

Influence of medium-chain triglycerides on lipid metabolism in the chick

The effect of corn oil, coconut oil, and medium-chain triglyceride (MCT, a glyceride mixture consisting almost exclusively of fatty acids of 8 and 10 carbons in length) ingestion on lipid metabolism was studied in chicks. In chicks fed cholesterol-free diets, MCT ingestion elevated plasma total lipids and cholesterol and depressed liver total lipids and cholesterol when compared to chicks receiving the corn oil diet. As a consequence of the opposite effects of MCT ingestion on plasma and liver cholesterol and total lipids, the plasma-liver cholesterol pool was not altered. When cholesterol was included in the diets, dietary MCT depressed liver and plasma total lipids and cholesterol as compared with corn oil, consequently also lowered the plasmaliver cholesterol pool. The in vitro cholesterol and fatty acid synthesis from acetate-1-¹⁴C was higher in liver slices from chicks fed MCT than in those from chicks fed corn oil. The percentage of radioactivity from acetate-1-¹⁴C incorporated into the carboxyl carbon of fatty acids by liver slices was not altered by MCT feeding, indicating that the increased acetate incorporation represented de novo fatty acid synthesis. The conversion of palmitate-1-¹⁴C to C₁₈ acids was increased in liver of chicks fed MCT, implying that fatty acid chain elongating activity was also increased. Studies on the conversion of stearate-2-¹⁴C to mono- and di-unsaturated C₁₈ acids showed that hepatic fatty acid desaturation activity was enhanced by MCT feeding. Data are presented on the plasma and liver fatty acid composition of chicks fed MCT-, corn oil-, or coconut oil-supplemented diets. The principles of laboratory animal care, as promulgated by the National Society for Medical Research, were observed.     

Dietary arachidonic acid and hepatic desaturation of fatty acids in obese zucker rats

The effect of low levels of dietary arachidonic acid (20:4n-6) on Δ6 desaturation of linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3), and on Δ5 desaturation of dihomo-γ-linolenic acid (20:3n-6) were studied in liver microsomes of obese Zucker rats, in comparison with their lean littermates. Fatty acid composition of serum total lipids and of phospholipids from liver microsomes and from total heart and kidney was determined to see whether modifications of desaturation rate, if any, were reflected in the tissue fatty acid profiles. Animals fed for 12 wk on a balanced diet, containing 20:4n-6 and 18:2n-6, were compared to those fed 18:2n-6 only. The low amount of dietary 20:4n-6 greatly inhibited Δ6 desaturation of 18:2n-6 and Δ5 desaturation of 20:3n-6, whereas Δ6 desaturation of 18:3n-3 was slightly increased in obese rats. Inhibition of the biosynthesis of long-chain n-6 fatty acids by dietary arachidonic acid was only slightly reflected in the 20:4n-6 content of liver microsome phospholipids. On the contrary, the enrichment of serum total lipids and heart and kidney phospholipids in this fatty acid was pronounced, more in obese than in lean animals. Our results show that, although the desaturation rate of the n-6 fatty acids in liver microsomes was greatly decreased by the presence of arachidonic acid in the diet, the tissue phospholipid content in arachidonic acid was not depressed. The potentiality of synthesis of eicosanoids of the 2 family from this fatty acid is consequently not lower, especially in obese rats, in which certain tissues are deficient in arachidonic acid, in comparison with their lean littermates.     

Fatty acyl desaturation in isolated hepatocytes from Atlantic salmon (Salmo salar): Stimulation by dietary borage oil containing γ-linolenic acid

The effects of different dietary oils on the fatty acid compositions of liver phospholipids and the desaturation and elongation of [1-¹⁴C]18∶3n−3 and [1-¹⁴C]18∶2n−6 were investigated in isolated hepatocytes from Atlantic salmon. Atlantic salmon smolts were fed diets containing either a standard fish oil (FO) as a control diet, a 1∶1 blend of Southern Hemisphere marine oil and tuna orbital oil (MO/TO), sunflower oil (SO), borage oil (BO), or oliver oil (OO) for 12 wk. The SO and BO diets significantly increased the percentages of 18:2n−6, 18:3n−6, 20:2n−6, 20:3n−6, and total n-6 polyunsaturated fatty acids (PUFA) in salmon liver lipids in comparison with the FO diet. The BO diet also increased the percentage of 20:4n−6. Both the SO and BO diets significantly reduced the percentages of all n−3 PUFA in comparison with the FO diet. The OO diet significantly increased the percentages of 18:1n−9, 18:2n−6, total monoenes, and total n−6 PUFA in liver lipids compared to the FO diet, and the percentages of all n−3 PUFA were significantly reduced. With [1-¹⁴C]18:3n−3, the recovery of radioactivity in the products of Δ6 desaturation was significantly greater in the hepatocytes from salmon fed SO, BO, and OO in comparison with the FO diet. The BO diet also increased the recovery of radioactivity in the products of Δ5 desaturation. Only the BO diet significantly affected the desaturation of [1-¹⁴C]18:2n−6, increasing recovery of radioactivity in both Δ6- and Δ5-desaturation products. In conclusion, dietary BO, enriched in γ-linolenic acid (18:3n−6), significantly increased the proportions of both 20:3n−6 and 20:4n−6 in salmon liver phospholipids and also significantly increased the desaturation of both 18:2n−6 and 18:3n−3 in salmon hepatocytes. The possible relationships between dietary fatty acid composition, tissue phospholipid fatty acid composition, and desaturation/elongation activities are discussed.