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Effect of gamma-butyrobetaine on fatty liver in juvenile visceral steatosis mice.

We pharmacokinetically examined the effect of gamma-butyrobetaine, a precursor of L-carnitine, on the change of fatty acid metabolism in juvenile visceral steatosis (JVS) mice, which have systemic L-carnitine deficiency due to lack of L-carnitine transporter activity. The concentrations of total free fatty acid (FFA), palmitic acid and stearic acid in the liver of JVS mice were significantly higher than those in wild-type mice. After intravenous administration of gamma-butyrobetaine (50 mg kg(-1)), the concentration of L-carnitine in the plasma of JVS mice reached about twice that of the control level and levels in the brain, liver and kidney were also significantly increased, whereas those in wild-type mice hardly changed. Although the plasma concentrations of FFA in both types of mice were unchanged after administration of gamma-butyrobetaine, the concentrations of palmitic acid and stearic acid were significantly decreased. In particular, the liver concentration of FFA in JVS mice was decreased to the wild-type control level, accompanied by significant decreases in long-chain fatty acids, palmitic acid and stearic acid, whereas those in wild-type mice were not changed. These results suggest that gamma-butyrobetaine can be taken up into organs, including the liver, of JVS mice, and transformed to L-carnitine. Consequently, administration of gamma-butyrobetaine may be more useful than that of L-carnitine itself for treatment of primary deficiency of carnitine due to a functional defect of the carnitine transporter.

Animals↗

Phosphatidylcholine synthesis in human spermatozoa.

To clarify the mechanism of phospholipid synthesis in spermatozoa, fresh human spermatozoa were incubated with labeled fatty acids and 1-acyl-lysophosphatidyl choline (LPC) in the presence or absence of coenzyme A (CoASH). Both docosahexaenoic acid and palmitic acid were incorporated into phosphatidylcholine; however, this reaction was absolutely dependent upon the presence of CoASH in the incubation medium. The rate of incorporation of docosahexaenoic acid was 2.7-fold higher than that of palmitic acid, but more palmitic acid was incorporated into phosphatidylcholine in the absence of LPC. These data provide direct evidence for acyl transferase activity in human spermatozoa and may furnish a mechanism for phospholipid remodeling in sperm membranes. The different incorporation rates of these fatty acids into phosphatidylcholine may be due to the kinetics of the activation step, long chain fatty acid:CoASH ligase (AMP), or the substrate specificity of the acyl transferase.

Coenzyme A↗

Tetradecylthioacetic acid (a 3-thia fatty acid) decreases triacylglycerol secretion in CaCo-2 cells.

The effects of the hypolipidemic fatty acid analogue tetradecylthioacetic acid (TTA) on synthesis and secretion of lipoproteins in CaCo-2 cells were studied. Radiolabeled tetradecylthioacetic acid was absorbed and metabolized as efficiently as oleic acid, although a discrepancy in the metabolic fate was evident. Whereas tetradecylthioacetic acid was incorporated into cell-associated triacylglycerol to the same extent as normal fatty acids (e.g., oleic acid and palmitic acid), the amount of triacylglycerol secreted from cells incubated with tetradecylthioacetic acid was 8 to 10 times lower than the amount secreted from cells incubated with palmitic acid and oleic acid, respectively. On the other hand, there was an enhanced incorporation of tetradecylthioacetic acid into cell-associated and secreted phospholipids. Despite incorporation of tetradecylthioacetic acid into cellular triacylglycerol, unlike oleic acid, tetradecylthioacetic acid did not stimulate production of triacylglycerol-rich particles. Ultracentrifugation of basolateral media from cells incubated with tetradecylthioacetic acid revealed low amounts of triacylglycerol in the triacylglycerol-rich fraction (p < 1.006 g/ml), suggesting secretion of lipoproteins with a higher density than chylomicrons. However, the present study shows that the stimulated triacylglycerol secretion caused by oleic acid was inhibited in the presence of TTA. The decreased rate of triacylglycerol secretion from these cells was not accompanied by a stimulation of fatty acid oxidation. Based on these findings, we therefore suggest that tetradecylthioacetic acid mainly affects secretion of lipoproteins in CaCo-2 cells.

Cell Line↗

Effects of diets enriched in lauric, palmitic or oleic acids on blood coagulation and fibrinolysis.

In this study we compared the effects of specific saturated fatty acids (lauric acid and palmitic acid) with those of a monounsaturated fatty acid (oleic acid) on coagulation and fibrinolytic parameters in healthy women and men. Eighteen women and fourteen men consumed, in random order, three experimental diets, each for six weeks. The diets consisted of solid foods and approximately 70% [28 percent of energy (En%)] of the fat calories was supplied. As determined from duplicate portions, in the lauric acid diet 7.3 En% and in the palmitic acid diet 6.1 En% of oleic acid were exchanged for lauric or palmitic acid, respectively. The lauric acid diet also contained some (average 1.8 En%) more myristic acid. Compared with the oleic acid diet, factor VIIam in the female subjects was 9% higher with the lauric acid diet (P = 0.0036; 95% CI, 3 to 14%) and 10% higher with the palmitic acid diet (P = 0.0011; 95% CI, 5 to 16%). Changes in men were not significant. Plasminogen Activator Inhibitor (PAI-1) activity was higher on the palmitic acid compared with the oleic acid diet (difference between diets of 2.3 U/ml; P = 0.0098; 95% CI, 0.4 to 4.3 U/ml) and the lauric acid diet (difference between diets of 2.2 U/ml; P = 0.0123; 95% CI, 0.2 to 4.1 U/ml). No significant differences between diets were observed for antithrombin III activity, fibrinogen concentrations, fragment 1+2 concentrations, plasminogen or alpha2-antiplasmin activity. From this study, we conclude that diets rich in lauric or palmitic acid, compared with a diet rich in oleic acid, unfavourably influence factor VIIam activity, in a gender specific manner. In addition, the plasminogen activator inhibiting capacity of the plasma is impaired with a palmitic acid rich diet compared with an oleic or lauric acid rich diet.

Adult↗

De novo fatty acid synthesis and elongation of fatty acids by subcellular fractions of lung.

Fatty acid synthesis by subcellular fractions of rabbit lung was studied by measuring the incorporation of either radioactive acetyl coenzyme A or malonyl coenzyme A into long-chain fatty acids. Evidence is presented to support the conclusions that the 95,000 g-supernatant fraction contains the enzymes, i.e., fatty acid synthetase and acetyl coenzyme A carboxylase, necessary for de novo fatty acid synthesis and is capable of synthesizing long-chain fatty acids, probably palmitic acid, under the appropriate conditions. The mitochondrial fraction incorporates the short-chain coenzyme A derivatives into fatty acids predominantly by the elongation pathway. It is suggested that the palmitic acid synthesized in vivo by the de novo fatty acid synthetic pathway, demonstrated in vitro in rabbit lung, may be a source of the lecithin palmitic acid utilized in the synthesis of pulmonary surfactant.

Adenosine Triphosphate↗

Conversion of alpha-linolenic acid to palmitic, palmitoleic, stearic and oleic acids in men and women.

The purpose of this study was to determine whether adult humans can recycle carbon from alpha-linolenic acid (18:3n-3) into saturated (SFA) and monounsaturated (MUFA) fatty acids. Six men and six women consumed 700 mg [U-13C]-18:3n-3. Blood was collected over 21 days and breath over 24h. [13C]-labelled SFA and MUFA were detected in plasma phosphatidylcholine (PC) and triacylglycerol (TAG). Total labelled fatty acid incorporation into SFA and MUFA was five- and 25-fold greater in PC than TAG in men and women, respectively. [13C]-16:0 was the major labelled fatty acid in both fractions. Total [13C] incorporation into SFA and MUFA was 20% greater in men than women, and related positively (r(2) = 0.35, P<0.05) to the fractional recovery of labelled 18:3n-3 as 13CO2 on breath. These results suggest that the extent of partitioning towards beta-oxidation and carbon recycling may regulate the availability of 18:3n-3 for conversion to longer-chain fatty acids.

Adult↗

Myristic acid, a rare fatty acid, is the lipid attached to the transforming protein of Rous sarcoma virus and its cellular homolog.

The lipid bound to p60src, the transforming protein of Rous sarcoma virus, has been identified by gas and thin-layer chromatography as the 14-carbon saturated fatty acid, myristic acid. The protein can be labeled biosynthetically with either [3H]myristic acid or [3H]palmitic acid. Incorporation of [3H]myristic acid was noticeably greater than incorporation of [3H]palmitic acid. All of the [3H]myristic acid-derived label in p60src was present as myristic acid. In contrast, none of the radioactivity derived from [3H]palmitic acid was recovered as palmitic acid. Instead, all 3H incorporated into p60src from [3H]palmitic acid arose by metabolism to myristic acid. The cellular tyrosine kinase, p60c-src also contains myristic acid. By comparison of the extent of myristylation of p60v-src with that of the Moloney murine leukemia virus structural protein precursor, Pr65gag, we estimate that greater than 80% of the molecules of p60v-src contain one molecule of this fatty acid. Myristylation is a rare form of protein modification. p60v-src contains 10 to 40% of the myristic acid bound to protein in cells transformed by Rous sarcoma virus and is easily identified in total cell lysates when [3H]myristic acid-labeled proteins are separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Comparison of the amount of [3H]myristic acid-labeled p60src in total cell lysates and in immunoprecipitates suggests that immunoprecipitation with rabbit anti-Rous sarcoma virus tumor sera detects ca. 25% of the p60src present in cells.

Animals↗

Effects of diet and simvastatin on fatty acid composition in hypercholesterolemic men: a randomized controlled trial.

OBJECTIVE: To explore the separate and combined effects of simvastatin and a low-saturated diet rich in alpha-linolenic acid on serum fatty acids. METHODS AND RESULTS: 120 hypercholesterolemic men were randomly allocated to a habitual diet or dietary treatment group and to receive, in random order, simvastatin 20 mg/d or placebo, each for 12 weeks, in a double-blind manner. Dietary treatment decreased proportions from total fatty acids of palmitic acid (C16:0) by 3.3% (P<0.05), stearic acid (C18:0) by 3.7% (P<0.05) and increased proportions of oleic acid (C18:1n-9) by 4.2% (P<0.01), and alpha-linolenic acid (C18:3n-3) by 29.8% (P<0.001). Simvastatin decreased proportions from total fatty acids of palmitic acid by 2.0% (P<0.01), linoleic acid (C18:2n-6) by 5.3% (P<0.001), and alpha-linolenic acid by 6.8% (P<0.05), and increased proportions of gamma-linolenic acid (C18:3n-6) by 11.1% (P<0.001), dihomo-gamma-linolenic acid (C20:3n-6) by 4.2% (P<0.01), arachidonic acid (C20:4n-6) by 14.2% (P<0.001), and the sum of long-chain polyunsaturated fatty acids (C20-22) by 9.0% (P<0.001). Simvastatin increased ratios of stearic to palmitic, gamma-linolenic to linoleic, and arachidonic to dihomo-gamma-linolenic acid by 7.6%, 17.0%, and 10.0% (P<0.001 for all), respectively, suggesting increased fatty acid elongase and Delta6- and Delta5-desaturase enzyme activities. CONCLUSIONS: Increased formation of long-chain polyunsaturated fatty acids and their metabolites may contribute a substantial part of the pleiotropic effects of simvastatin.

Adult↗

Distinct effects of saturated and monounsaturated fatty acids on beta-cell turnover and function.

Glucotoxicity and lipotoxicity contribute to the impaired beta-cell function observed in type 2 diabetes. Here we examine the effect of saturated and unsaturated fatty acids at different glucose concentrations on beta-cell proliferation and apoptosis. Adult rat pancreatic islets were cultured onto plates coated with extracellular matrix derived from bovine corneal endothelial cells. Exposure of islets to saturated fatty acid (0.5 mmol/l palmitic acid) in medium containing 5.5, 11.1, or 33.3 mmol/l glucose for 4 days resulted in a five- to ninefold increase of beta-cell DNA fragmentation. In contrast, monounsaturated palmitoleic acid alone (0.5 mmol/l) or in combination with palmitic acid (0.25 or 0.5 mmol/l each) did not affect DNA fragmentation. Increasing concentrations of glucose promoted beta-cell proliferation that was dramatically reduced by palmitic acid. Palmitoleic acid enhanced the proliferation activity in medium containing 5.5 mmol/l glucose but had no additional effect at higher glucose concentrations (11.1 and 33.3 mmol/l). The cell-permeable ceramide analog C2-ceramide mimicked both the palmitic acid-induced beta-cell apoptosis and decrease in proliferation. Moreover, the ceramide synthetase inhibitor fumonisin B1 blocked the deleterious effects of palmitic acid on beta-cell viability. Additionally, palmitic acid but not palmitoleic acid decreased the expression of the mitochondrial adenine nucleotide translocator and induced release of cytochrome c from the mitochondria into the cytosol. Finally, palmitoleic acid improved beta-cell-secretory function that was reduced by palmitic acid. Taken together, these results suggest that the lipotoxic effect of the saturated palmitic acid involves an increased apoptosis rate coupled with reduced proliferation capacity of beta-cells and impaired insulin secretion. The deleterious effect of palmitate on beta-cell turnover is mediated via formation of ceramide and activation of the apoptotic mitochondrial pathway. In contrast, the monounsaturated palmitoleic acid does not affect beta-cell apoptosis, yet it promotes beta-cell proliferation at low glucose concentrations, counteracting the negative effects of palmitic acid as well as improving beta-cell function.

Animals↗

Acylation of lysolecithin in the intestinal mucosa of rats.

1. The presence of an active acyl-CoA-lysolecithin (1-acylglycerophosphorylcholine) acyltransferase was demonstrated in rat intestinal mucosa. 2. ATP and CoA were necessary for the incorporation of free [1-(14)C]oleic acid into lecithin (phosphatidylcholine). 3. The reaction was about 20 times as fast with [1-(14)C]oleoyl-CoA as with free oleic acid, CoA and ATP. 4. With 1-acylglycerophosphorylcholine as the acceptor, both oleic acid and palmitic acid were incorporated into the beta-position of lecithin; the incorporation of palmitic acid was 60% of that of oleic acid. 5. Of the various analogues of lysolecithin tested as acyl acceptors from [1-(14)C]oleoyl CoA, a lysolecithin with a long-chain fatty acid at the 1-position was most efficient. 6. The enzyme was mostly present in the brush-border-free particulate fraction of the intestinal mucosa. 7. Of the various tissues of rats tested for the activity, intestinal mucosa was found to be the most active, with testes, liver, kidneys and spleen following it in decreasing order.

Acyltransferases↗

Effects of alpha lipoic acid, ascorbic acid-6-palmitate, and fish oil on the glutathione, malonaldehyde, and fatty acids levels in erythrocytes of streptozotocin induced diabetic male rats.

In this research, it has been aimed to evaluate the improvement effects of alpha lipoic acid (ALA), ascorbic acid-6-palmitate (AA6P), fish oil (FO), and their combination (COM) on some biochemical properties in erythrocytes of streptozotocin (STZ)-induced diabetic male rats. According to experimental results, glutathione (GSH) level in erythrocytes decreased in diabetes (P < 0.01), D + ALA, and D + AA6P groups (P < 0.001). Malonaldehyde (MA) level increased in diabetes (P < 0.05), D + FO, and D + COM groups (P < 0.001), but its level in D + AA6P and D + ALA groups was lower in diabetes group (P < 0.01). Total lipid level in diabetes and diabetes plus antioxidant administered groups were higher than control. Total cholesterol level was high in diabetes and D + ALA groups (P < 0.05), but its level reduced in D + FO compared to control and diabetes groups, P < 0.05, < 0.001, respectively. Total triglyceride (TTG) level was high in the D + ALA (P < 0.05) and D + COM (P < 0.001) groups. In contrast, TTG level in blood of diabetes group was higher than diabetes plus antioxidant and FO administered groups (P < 0.001). According to gas chromatography analysis results, while the palmitic acid raised in diabetes group (P < 0.05), stearic acid in D + FO, D + ALA, and diabetes groups was lower than control (P < 0.05), oleic acid reduced in D + COM and D + FO groups, but its level raised in D + AA6P and D + ALA groups (P < 0.01). As the linoleic acid (LA) elevated in ALA + D, D + AA6P, and diabetes groups, linolenic acid level in diabetes, D + AA6P, and D + FO groups was lower than control (P < 0.001). Arachidonic acid (AA) decreased in D + ALA, D+ AA6P, and diabetes groups (P < 0.01), but its level in D + COM and D + FO was higher than control (P < 0.05). Docosahexaenoic acid (DHA) increased in D + AA6P and D + COM (P < 0.05). While the total saturated fatty acid level raised in diabetes group, its level reduced in D + ALA and D + FO groups (P < 0.05). In contrast, total unsaturated fatty acid level in D + ALA and D + FO groups was higher than control (P < 0.05). In conclusion, present data have confirmed that the combination of the ALA, AA6P, and FO have improvement effects on the recycling of GSSG to reduced GSH in erythrocytes of diabetic rats, and in addition to this, oxidative stress was suppressed by ALA and AA6P, and unsaturated fatty acid degree was raised by the effects of ALA and FO.

Animals↗

Thr268 in substrate binding and catalysis in P450BM-3.

Members of the gene superfamily of proteins called "P450" catalyze monooxygenation reactions that require an input of two electrons and a molecule of oxygen per catalytic cycle. These proteins are widely distributed among living organisms, from bacteria to human. P450BM-3, a soluble protein isolated from Bacillus megaterium, is self-sufficient, containing P450 and reductase domains on the same polypeptide. P450BM-3 catalyzes the hydroxylation of various fatty acids at omega-1, omega-2, and omega-3 positions, as well as epoxidations of double bonds. We have constructed the active-site mutant, T268A, and analyzed the effect on arachidonic acid and palmitic acid oxidation. Data indicate that the mutation changes the coupling (ratio of NADPH consumed versus product formed) for both arachidonic acid and palmitic acid oxidation. We have also analyzed cumene hydroperoxide-driven reactions and shown that they are unaffected by this mutation. These data, as well as fatty acid binding studies, support the hypothesis of a role of the I-helix residue, T268, in maintaining fatty acid substrates in the correct position for productive hydroxylation during the catalytic cycle of this enzyme.

Arachidonic Acid↗

Chemical analysis and nutritional assessment of the less known pulses, Vigna aconitifolia (Jacq.) Marechal and Vigna vexillata (L.) A. Rich.

The seeds of Vigna aconitifolia and Vigna vexillata were analysed for proximate composition, minerals, seed protein fractions, amino acids, fatty acids, and antinutritional factors. Both the pulses were found to be rich sources of proteins and minerals like Ca, Mg, Fe, Zn, and Mn. Vigna aconitifolia seeds exhibited fairly high levels of crude lipid. The most limiting essential amino acids in both the pulses were the sulphur-amino acids, cystine, and methionine. Threonine in V. aconitifolia and phenylalanine and tyrosine in V. vexillata occurred in higher quantities when compared with WHO/FAO requirement pattern. Oleic acid and palmitic acid in V. aconitifolia and linoleic acid and palmitic acid in V. vexillata lipids were found to be the predominant fatty acids. The tannin content of both the pulses was negligible compared with the domesticated legumes. The other antinutritional factors like total free phenols, L-DOPA and haemagglutinating activity were also analysed/assayed.

Amino Acids↗

Influence of sex and gonadal hormones on rat-liver and carcass lipids during the development of an essential fatty acid deficiency.

1. Groups of intact male and female rats and castrated rats injected with oestradiol or testosterone were given a diet containing hydrogenated coconut oil for 9 weeks, and at intervals the amounts and fatty acid compositions of the carcass and liver lipids were determined. 2. Male rats grew faster and larger, and exhibited typical external essential fatty acid deficiency symptoms sooner than did females. Testosterone-treated castrated male rats were similar to males, and oestradiol-injected castrated male rats resembled females. 3. Intact females maintained a higher linoleic acid concentration in their carcass than did males. Total amounts of carcass linoleic acid remained similar for all groups, only 200mg. being removed in 9 weeks regardless of body size. 4. The amounts of total cholesteryl esters were independent of liver size. They were higher in males and testosterone-treated castrated male rats than in females and oestrogen-treated castrated male rats. 5. Phospholipids represented about 80% of the liver lipids. The total amounts of the phospholipid linoleic acid and arachidonic acid were similar for all groups regardless of liver size, and were not affected appreciably by the deficiency. Females and oestrogen-treated castrated male rats maintained a higher proportion of phospholipid arachidonic acid for longer periods than did their male counterparts. Both the total amounts and the proportions of eicosatrienoic acid and palmitic acid were higher in males than in females. 6. Supplementation of the essential fatty acid-deficient diet with linoleic acid caused a rapid loss of eicosatrienoic acid and palmitic acid with a concomitant increase in stearic acid and arachidonic acid. 7. There were no obvious differences in the way that the essential fatty acids were metabolized or mobilized from adipose tissue of male or female rats during essential fatty acid deficiency. 8. The results indicated that the greater growth rate of the male rats caused them to require and synthesize more phospholipids than did the females. In the absence of adequate amounts of arachidonic acid, eicosatrienoic acid was substituted into the additional phospholipid. The earlier symptoms of essential fatty acid deficiency in the male rat could therefore be ascribed to the higher tissue concentrations of this unnatural phospholipid and its inability to perform the normal metabolic functions of phospholipids.

Journal Article↗

Control of liposidomycin production through precursor-directed biosynthesis.

Liposidomycin, a potent inhibitor of bacterial peptidoglycan biosynthesis, represents the main component of a group of over 24 closely related, fatty acyl nucleoside antibiotics produced by Streptomyces. Exogeneously supplied myristic acid or palmitic acid resulted in the almost exclusive production of liposidomycin C-(III) and/or M-(III). Exogeneously supplied [1-13C]-palmitic acid was incorporated directly into liposidomycin M-(III) as judged by the FAB-MS and 13C NMR spectra.

Aminoglycosides↗

Chronic effects of different fatty acids and leptin in INS-1 cells.

The effects of long-term exposure of a pancreatic beta cell line, INS-1, to major free fatty acids (FFA; palmitic acid, oleic acid and linoleic acid) and leptin on insulin secretion and cell viability by C,N-diphenyl-N'-4,5 dimethylthiazol 2-yl tetrazolium bromide (MTT) assay were examined. The cells were incubated with 1 mmol/l of each FFA and 25 or 100 ng/ml leptin, alone or in combination, for 4, 24 or 48 h before the insulin secretion experiments. Palmitic acid (C 16:0) significantly suppressed cell viability, and suppressed insulin secretion at 24 h. Treatment with oleic acid (C 18:1) or linoleic acid (C 18:2) enhanced basal insulin secretion and diminished glucose-stimulated insulin secretion (GSIS) at 48 h. In these groups, there were no differences in cell viability as compared to cells treated without FFA. Leptin did not affect insulin secretion at 4, 24 and 48 h, and in the cells co-treated with FFA and leptin, leptin did not ameliorate lipotoxicity. These results suggest that, in INS-1 cells, different FFA have different patterns of lipotoxicity with chronic exposure, and leptin has little direct effect on insulin secretion.

Animals↗

Eicosapentaenoic acid causes transient accumulation of lipids in rat myocardium.

Rats were given eicosapentaenoic acid (EPA) or palmitic acid (PALM) up to 15 days, and control animals were given carboxymethylcellulose. All suspensions which were given by gastric intubation contained tocopherol. Heart triacylglycerols, heart cholesterol and heart phospholipids significantly increased after one day of EPA treatment, but they were normalized within 15 days. Both after 2 and 10 days of treatment with palmitic acid the heart triacylglycerols were significantly greater than control. The heart cholesterol and heart phospholipids were significantly greater than control after 10 days of treatment with palmitic acid. Total carnitine palmitoyltransferase (CPT) activity in heart was significantly greater in rats treated with EPA for 15 days compared to control, but treatment with palmitic acid had no effect. The fatty acyl-CoA oxidase activity was greater in rats treated with EPA for 15 days and palmitic acid for 10 days compared to control. The fractional volume of lipid droplets in myocardial cells was calculated from electronmicrographs and was 0.112 +/- 0.016% after 1 day of EPA treatment compared to 0.035 +/- 0.016% in the control group. After 5 and 15 days the fractional volume was the same as control. The fractional volume of lipid droplets in rats treated with palmitic acid for 10 days was 0.120 +/- 0.023%. Treatment with EPA caused an immediate accumulation of lipids and lipid droplets in the rat heart which after few days normalized in parallel with an increased activity of total CPT in the heart.

Acyl-CoA Oxidase↗

Microsomal desaturation of stearic acid in relation to lymphocyte activation.

The conversion of stearic acid to oleic acid (delta 9-desaturase) was followed in mouse thymocytes stimulated by either concanavalin A or concanavalin A + interleukin-2 resulting in different rates of cell proliferation. To estimate the plasma membrane turnover of oleic acid as compared to that of a saturated fatty acid, double-label experiments ([14C]oleic acid, [3H]palmitic acid) were performed. Following an inhibition delta 9-desaturase was found to be activated from the fourth hour of stimulation. In the early period of cell activation this process proved to be independent of protein synthesis, whereas in the stage of proliferation it was dependent on it. Increased membrane fluidity in the first 30 min of activation is not likely due to enrichment of oleic acid. Cell proliferation and microsomal desaturation seem to be coupled and an increasing amount of oleic acid is at least one of the factors resulting in increased fluidity of the surface membrane of proliferating cells.

Animals↗