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At least 19 recordsLinked to original sources
PubMed1977

Involvement of cytochrome b5 in the oxidative desaturation of linoleic acid to gamma-linolenic acid in rat liver microsomes.

The effects of antibodies against microsomal electron-transport components on the in vitro activity of delta6-desaturation of linoleic acid to gamma-linolenic acid have been studied in intact microsomal membranes of rat liver. Reduced nicotinamide adenine dinucleotide (NADH) or reduced nicotinamide adenine dinucleotide phosphate (NADPH) (0.87 mM) served as electron donors, and effectively prompted the delta6-desaturase activities with yields of about 1.1 to 1.3 nmol per mg of protein in 10 min. Of the two antibodies studied under the same in vitro conditions, i.e., rabbit antisera preparations against rat liver microsomal hydrophilic parts of cytochrome b5 and NADPH-cytochrome c reductase, only the antibody against cytochrome b5 demonstrated a marked ability to inhibit the delta6-desaturase activity. This evidence supports a participation of cytochrome b5 in the delta6-desaturation of linoleic acid and suggests a pathway analogous to the delta9-desaturation of stearyl-CoA.

Animals↗
PubMed1978

[Effect of dietary alpha-linolenic acid on the conversion of linoleic and gamma-linolenic acids (1-14C) into arachidonates in rats in vivo].

The effects of alpha-linolenic acid (9-12-15 octadecadienoic) upon the conversion in vivo of [1-14C] linoleic acid and of [1-14C] gamma-linolenic acid into arachidonate have been studied in adult rats. The two tracers have been administered by stomach tubing and the amounts of [14C]-radioactivity incorporated into arachidonate in the liver, kidneys and whole rat have been measured 48 h later. Three experiments have been carried out on rats fed on alpha-linolenic acid containing diets prior to the radioactive tubing. In these diets, alpha-linolenic acid was brought either as ethyl ester or in the form of Primor oil (erucic acid free rapeseed oil). In all of them, the ratio alpha-linolenic acid: linoleic acid did not exceed 0.45. Control animals were fed, in the same conditions, ethyl oleate or peanut oil respectively. Comparing the alpha-linolenic acid fed-rats to the control animals, we were able to observe the following results: (1) The exogenous supplies of alpha-linolenic acid used in the diets have not brought about any significant alteration in the amounts (weights) of arachidonic acid present in the liver, kidneys and whole animal. (2) Using [1-14C] linoleic acid as a precursor, the amounts of [14C]-radioactivity incorporated into arachidonate in the same organs as well as in the whole rat have been significantly lowered by dietary alpha-linolenate. (3) alpha-Linolenate, on the contrary, had no significant effect upon the amounts of radioactivity incorporated into hepatic, renal and whole body arachidonate following the administration of [1-14C] gamma-linolenic acid. These results lead to the conclusion that alpha-linolenic acid, when present in the diet of rats at a limited, phyisological level, partly inhibits the desaturation of linoleic acid in vivo but does not affect the subsequent reactions in the biosynthesis of arachidonic acid.

Animals↗
PubMed1979

The nutritional regulation of T lymphocyte function.

Prostaglandin (PG) E1 plays a major role in the regulation of thymus development and T lymphocyte function and the evidence for this is reviewed. The production of PGE1 is dependent on nutritional factors with linoleic acid, gamma-linolenic acid, pyridoxine, zinc and vitamin C playing key roles. Inadequate intake of any one of these will lead to inadequate PGE1 formation and defective T lymphocyte function. Megadoses of any one are likely to be only minimally effective in the absence of adequate intakes of the others. By careful attention to diet it should be possible to activate T lymphocyte function in the large number of diseases including rheumatoid arthritis, various auto-immune diseases, multiple sclerosis, and cancer in which such function is defective. It is possible that T lymphocytes may require both endogenous and exogenous PGE1 in order to function adequately. It is therefore of particular interest that many cancer cells and virally infected cells are unable to make PGE1 because they cannot convert linoleic acid to gamma-linolenic acid. The direct provision of gamma-linolenic or dihomo-gammalinolenic acids in these situations is worthy of full investigation.

Animals↗
PubMed1976

Comparative effect of glucagon, dibutyryl cyclic AMP, and epinephrine on the desaturation and elongation of linoleic acid by rat liver microsomes.

The effect of glucagon, dibutyryl cyclic adenosine 3',5'-monophosphate, and epinephrine on the biosynthesis of polyunsaturated fatty acids of the linoleic acid family was studied. The incubations were performed with rat liver microsomes and labeled linoleic acid under desaturating and elongating conditions. Under desaturating conditions linoleic acid was converted to gamma-linolenic acid, whereas under elongating conditions it was converted to 20:2omega6. Glucagon, dibutyryl cyclic AMP, and epinephrine decreased the oxidative desaturation of linoleic acid to gamma-linolenic acid while the elongating reaction was not modified in the experimental conditions tested. Consequently, the results support the hypothesis that the oxidative desaturation of linoleic acid to gamma-linolenic acid is the main controllable step in the biosynthesis of polyunsaturated fatty acids of the linoleic acid family in the microsomes.

Animals↗
PubMed1979

Correlation between fluidity and fatty acid composition of phospholipid species in Tetrahymena pyriformis during temperature acclimation.

The correlation between the fluidity of phospholipids and their fatty acid composition was studied by spin label technique and gas-liquid chromatography for three major phospholipid species in Tetrahymena pyriformis during temperature acclimation. The fluidity of 2-aminoethylphosphonolipid increased within the first 10 h of the cold-acclimation when the content of gamma-linolenic acid in 2-aminoethylphosphonolipid was highest, and it then decreased up to 24 h. On the other hand, the fluidities of phosphatidylethanolamine and phosphatidylcholine showed a gradual decrease up to 24 h after the temperature shift, although gamma-linolenic acid contents were highest at 10 h after the temperature shift. Thus the fluidity changes of these two phospholipids were interpreted as resulting from the altered content of other fatty acids in addition to gamma-linolenic acid, since the gamma-linolenic acid content was smaller than that of 2-aminoethylphosphonolipid. The results suggest that the content of gamma-linolenic acid in 2-aminoethylphosphonolipid plays a role in regulating the thermal adaptation process.

Acclimatization↗
PubMed1977

Evidence for participation of cytochrome b5 in microsomal delta-6 desaturation of fatty acids.

The delta-6 desaturation of linoleic acid to gamma-linolenic acid and oleic acid to 6,9-octadecadienoic acid by rat liver microsomes was investigated. Using a specific antibody prepared against purified rat liver cytochrome b5, we demonstrated that cytochrome b5 participated in delta-6 desaturation of both fatty acids. The reaction products were identified as their methyl ester derivatives by argentation thin-layer chromatography, gas-liquid chromatography, and reductive ozonolysis followed by gas-liquid chromatography.

Animals↗
PubMed1975

Effects of glucagon and dibutyryl adenosine 3', 5'-cyclic monophosphate on oxidative desaturation of fatty acids in the rat.

The present work was undertaken to study the effect of anti-insulinic and glycogenolytic factors on the oxidative desaturation of fatty acids. The effects of glucagon and dibutyryl cyclic AMP on the desaturation of linoleic acid to gamma-linolenic acid, alpha-linolenic acid to octadeca-6,9,12,15-tetraenoic acid, stearic acid to oleic acid, and eicosa-8,11,14-trienoic acid to eicosa-5,8,11,14-tetraenoic acid by rat liver microsomal preparations were investigated. Fasted rats had low desaturating activity, but refeeding a fat-free diet enhanced the activity. Administration of glucagon or dibutyryl cyclic AMP abolished the increase of the 6-desaturase activity elicited by refeeding. However, a similar effect on the 9-desaturase and 5-desaturase activity was not observed. The relationship between these effects and glucose metabolism is discussed.

Animals↗
PubMed1976

Effect of epinephrine on the oxidative desaturation of fatty acids in the rat.

The effect of epinephrine on the oxidative desaturation of fatty acids by liver microsomal preparations of rats has been studied. Administration of epinephrine (1 mg/kg body weight) produced a significant decrease in desaturation of [l-14C]=linoleic acid to gamma-linolenic acid and of [L-14C]alpha-linolenic acid to actadeca-6,9,12,15-tetraenoic acid 12 hr after the infection. Lower doses produced a lesser effect on the delta6-desaturation activity. Epinephrine administration modified the V max of linoleic acid desaturation but not the K m. There was also a slight increase in palmityl desaturation activity. The effect of epinephrine on delta6-desaturation activity was postulated to be mediated through an enhancement of the intracellular cyclic AMP levels that lead to an increase of a glucose metabolite. This metabolite would inhibit delta6-desaturation activity.

Animals↗
PubMed1978

Effect of catecholamines and beta-blockers on linoleic acid desaturation activity.

The effect of catecholamines and adrenergic blocking agents on the oxidative desaturation of linoleic acid in rat liver microsomes was studied. Epinephrine (1 mg/kg/body weight) produced a significant decrease on the conversion of [1-14C]linoleic acid to gamma-linolenic acid. The effect of epinephrine was blocked by single injections of the beta blockers propranolol (10 mg/kg body weight) or dichloroisoproterenol 30 min before the hormone treatment. Isoproterenol (100 microgram/kg body weight) produced a significant decrease on the activity of the linoleyl-CoA desaturase. The effect of the catecholamines was postulated to be mediated through beta receptors by an enhancement of the intracellular levels of cyclic AMP.

Adrenergic beta-Antagonists↗
PubMed1976

Effect of variou cultural conditions on the fatty acid and lipid composition of Choanephora cucurbitarum.

The fatty acid composition of the total and polar lipid fractions of Choanephora cucurbitarum grown under different cultural conditions were analyzed by thin-layer and gas-liquid chromatography. It was observed that temperature, age, pH, and light influenced the degree of unsaturation, this being due mainly to changes in the gamma-linolenic acid concentration. The conditions used in this study did not alter the qualitative profile of fatty acids normally present in the organism. Neither did these conditions stimulate the production of further long-chain fatty acids (C20-C26) beyond gamma-linolenic acid (C18:3) as reported earlier using growth media containing glutamic acid. The fatty acid pattern of lipid fractions though the same qualitatively, differed quantitatively. The polar lipid fractions, phosphatidyl choline, phosphatidyl ethanolamine, and diphosphatidyl glycerol showed an appreciable variation in gamma-linolenic acid content under different cultural conditions. The degree of unsaturation of the various lipid fractions decreased with increases in temperature, light intensity, and pH, but within each treatment the same pattern of decreasing degree of unsaturation with increasing age was observed. The significance of these observations is discussed.

Fatty Acids↗
PubMed1979

Modification of membrane lipids. Phenethyl alcohol-induced alteration of lipid composition in Tetrahymena membranes.

Tetrahymena pyriformis NT-I cells in the early-logarithmic phase were incubated with phenethyl alcohol (2-phenylethanol) and effects on the lipid composition were examined in various membranes. 1. There was a marked modification in phospholipid head, as well as fatty acyl group composition in pellicles, mitochondria and microsomes of the phenethyl alcohol-treated cells. Compared with membranes of the control cells, the membranes from phenethyl alcohol-treated cells were found to contain a higher level of phosphatidylcholine content with the compensating decrease in phosphatidylethanolamine, while 2-aminoethylphosphonolipid showed only a slight decrease in these membranes. The acyl group profile of membrane phospholipids in the presence of phenethyl alcohol was also modified so that a profound elevation of the content of polyunsaturated fatty acids, linoleic and gamma-linolenic acids. The major monounsaturate, palmitoleate decreased. Such lipid alteration is a reversible process, and therefore upon removal of phenethyl alcohol the modified lipid composition returned to normal. 2. By freeze-fracture electron microscopy in combination with temperature quenching, the outer alveolar membrane of the phenethyl alcohol-treated cell was observed to reveal less aggregation of intercalated-membrane particles, as compared with the control membrane. The quantitative analysis of the thermotropic lateral movement of membrane particles provided evidence that the membrane in the phenethyl alcohol-treated cell became more fluid. Such fluidizing effects may result from an increase in the acyl group unsaturation and also in the phosphatidylcholine content. 3. With regard to the mechanism responsible for the marked decrease in palmitoleate in membrane phospholipids, there was found a depressed conversion of the palmitate to palmitoleate in the phenethyl alcohol-treated cells. It was further suggested that the drug may have an inhibitory effect on the synthesis of palmitoyl-CoA desaturase involving the (16 : 0 leads to 16 : 1) conversion. Also, it was demonstrated that the increase in a precursor-product fashion of phosphatidylcholine with the corresponding decrease in phosphatidylethanolamine was not due to transformation of phosphatidylethanolamine to phosphatidylcholine through stepwise methylation.

Animals↗
PubMed1978

Polyunsaturated fatty acids in treatment of acute remitting multiple sclerosis.

One hundred and sixteen patients with acute remitting multiple sclerosis (MS) took part in a double-blind controlled trial of treatment with polyunsaturated fatty acids and were randomly allocated to one of four groups. Two groups received linoleic acid, one alone as a spread and one with gamma-linolenic acid in capsules (Naudicelle); and two control groups received oleic acid, one as a spread and one in capsules. Rates of clinical deterioration and frequencies of attacks were not significantly different between treated and control groups. Exacerbations were shorter and less severe in patients receiving a high dose of linoleic acid than in controls, but those receiving a lower dose--that is, Naudicelle--showed no such difference. Thus supplementing the diet with 20 g linoleic acid marginally affected the duration and severity of relapses of MS but had no effect on overall disability. The dose of Naudicelle used provided insufficient supplementation.

Adult↗
PubMed1978

Prostaglandin endoperoxides promote calcium release from a platelet membrane fraction in vitro.

A calcium sequestering platelet membrane fraction was prepared and the effect of arachidonic acid, PGG2 and PGH2 on calcium content evaluated. At 4 degrees C, 6.7--16.7 micrometers arachidonic acid caused significant release of calcium from preloaded vesicles. Such release was completely inhibited by aspirin pretreating the platelets from which the membrane fraction was prepared. Gamma-linolenic acid, not a substrate for prostaglandin synthesis, did not cause calcium release. At 37 degrees C, after a 5 minute calcium loading of the membrane vesicles, arachidonic acid, PGG2, and PGH2 caused release of calcium. Calcium release by the PGG2 and PGH2 was only slightly inhibited by aspirin. Imidazole, which prevented conversion of the prostaglandin endoperoxides to thromboxanes, also only slightly inhibited calcium release. Other prostaglandins including PGD2, PGE1, PGE2 and PGD2 had no effect on the calcium content of the vesicles. These studies suggest that PGG2 and PGH2 may exert their effects on platelets by mobilizing calcium from an internal membrane store to make it available to promote platelet activation.

Arachidonic Acids↗
PubMed1979

Positional distribution of fatty acids in the glycerophospholipids of Tetrahymena pyriformis.

The positional distributions of the fatty acids in the major glycerophospholipids of Tetrahymena pyriformis W were analyzed. A comparison was made of the acyl distributions in normal and ergosterol-grown cells. It was assumed that the positional arrangement of fatty acids would serve as an indicator of acyltransferase enzyme specificity. The acyltransferases in this protozoan have substrate specificities that direct unsaturated groups, particularly polyunsaturates, to the 2-carbon of the glycerophospholipids. An exception is gamma-linolenic acid, which represents a substantial proportion of the total acids at both carbons. Saturated and iso-acids are esterified primarily at the 1-carbon. The qualitative pattern of the fatty acyl distribution is the same in both normal and ergosterol-grown organisms. Sterol substitution produces quantitative differences in the acyl components at both the 1- and 2-carbons of the glycerophospholipids. These differences include a shortening of the average chain length and a decrease in total unsaturation at both the 1- and 2-positions. In addition, there is a modification at the 2-carbon in the relative amounts of the products of two pathways involved in the biosynthesis of fatty acids. The data are interpreted to indicate that the fatty acid transformations in the glycerophospholipids of organisms that contain ergosterol are not the result of altered acyltransferase specificities.

Acyltransferases↗
PubMed1979

Differential biosynthesis of polyunsaturated fatty acids by Tetrahymena supplemented with ergosterol.

Tetrahymena grown with foreign sterols such as ergosterol incorporate them into cellular membranes at the expense of the native compound, tetrahymanol. It is shown that cells grown with ergosterol have a lessened capacity to produce the polyunsaturated linoleic and gamma-linolenic acids from [14C]oleic acid. However, the same cells have normal capacities to introduce double bonds at C-6 into linoleate, alpha-linolenate, or cis-vaccenate. Thus, a presumed 12-desaturase is inhibited in the presence of ergosterol, while desaturation at C-6 is unaffected.

Ergosterol↗
PubMed1979

Studies on temperature adaptation in Tetrahymena. Positional distribution of fatty acids and species analysis of phosphatidylethanolamine from Tetrahymena pyriformis grown at different temperatures.

Phosphatidylethanolamine of 15 degrees C-grown Tetrahymena pyriformis (NT-I) cells contains more polyunsaturated fatty acids than 39.5 degrees C-grown cells. This increase in unsaturation is due to an increase in linoleic (C18 : 2) and linolenic (C18 : 3) acids, and a decrease in myristic (C14 : 0), palmitic (C16 : 0), palmitoleic (C16 : 1) and heptadecanoic (C17 : 0) acids. Compared with 39.5 degrees C-grown cells, the proportion of palmitic acid (C16 : 0) decreased in the 1-position as does at the 2-position in 15 degrees C-grown cells. On the contrary, there is a significant increase in linoleic (C18 : 2 delta 9, 12) and gamma-linolenic (gamma-C18 : 3) acids in the 1- and 2-positions, respectively. Phosphatidylethanolamine has been subfractionated into seven different diglyceride species. In 15 degrees C cells, the amounts of fractions 2 (1-linolenoyl-2-linoleoyl) and 3 (1-linolenoyl-2-palmitoleoyl, 1-linolenoyl-2-oleoyl) increased while there was a great decrease in subfraction 7 (1-myristoyl-2-palmitoleoyl, 1-palmitoyl-2-palmitoleoyl). Since subfractions 1 and 2 contain over 70% linoleic (C18 : 2) and linolenic (C18 : 3) acids, these fractions might be composed mainly of 1-linolenoyl-2-linolenoyl and 1-linolenoyl-2-linoleoyl molecular species at 15 degrees C. These data support evidence that phosphatidylethanolamine would play a principal role as an acceptor of acyl chains for temperature acclimation.

Adaptation, Physiological↗