Decrease In Arachidonic Acid Research Articles

Effects of dietary cod liver oil on fatty-acid composition and calcium transport in isolated adult rat ventricular myocytes and on the response of isolated hearts to ischemia and reperfusion.

Three-week-old male and female rats were placed either on standard rat chow or chow supplemented with 10% cod liver oil for 12 weeks. Animals fed cod liver oil demonstrated reduced body weights. Cod liver oil feeding produced a significant reduction in the ratio of (n - 6)/(n - 3) fatty acids in phospholipids of the isolated myocytes. The primary changes included a significant decrease in arachidonic acid (20:4, n - 6) and elevations in eicosapentaenoic acid (20:5, n - 3) and docosahexaenoic acid (22:6, n - 3). Furthermore, isolated myocytes from cod liver oil fed rats exhibited an enhanced 45Ca2+ uptake, although 45Ca2+ release was unaffected. Dietary cod liver oil had little effect on cardiac response to ischemia and reperfusion. Thus, neither developed force or resting tension was significantly affected by diet, although the latter tended to be elevated in hearts from cod liver oil fed animals. Release of creatine kinase was unaltered by diet. The release of 6-ketoprostaglandin F1 alpha from isolated hearts was significantly reduced by dietary cod liver oil, likely due to the reduced levels of arachidonic acid. Our study indicates that dietary cod liver oil and subsequent changes in phospholipid fatty-acid content are accompanied by changes in Ca2+ transport in isolated cardiac myocytes. However, this diet produces little effect on the cardiac response to acute ischemia and reperfusion.

Effects of dietary fish oil supplementation on polymorphonuclear leukocyte inflammatory potential.

Polymorphonuclear leukocytes (PMNLs) are an important contributor to inflammation and are thus a part of the pathophysiology of many human diseases. We assessed the effect of fish oil on PMNL inflammatory potential by measuring chemiluminescence and superoxide production before and after six weeks of daily cod liver oil ingestion by healthy volunteers. Phagocytosing PMNLs demonstrated a 27% decrease in chemiluminescence (P less than 0.05) and a 64% decrease in superoxide production (P less than 0.01), following the cod liver oil supplementation. Analysis of PMNL and platelet fatty acids revealed the appearance of eicosapentaenoic acid and a significant decrease in arachidonic acid in both types of cells.

Effects of dietary linolenate on the fatty acid composition of brain lipids in rats.

Weanling male rats were fed hydrogenated coconut oil to induce essential fatty acid (EFA) deficiency. After 15 weeks, the rats were divided into six groups. Five groups were fed graded amounts of purified linolenate (18:3 omega 3) with a constant amount of linoleate (18:2 omega 6) for six weeks. Fatty acid composition was determined in brain lipids. Increasing dietary 18:3 omega 3 resulted in a decrease in arachidonic acid (20:4 omega 6), docosatetraenoic acid (22:4 omega 6) and docosapentaenoic acid (22:5 omega 6), whereas 18:2 omega 6 and eicosatrienoic acid (20:3 omega 6) were increased both in total lipids and phospholipids. These results suggest that dietary 18:3 omega 3 exerts its inhibitory effect mainly on the desaturation of 20:3 omega 6 to 20:4 omega 6 in brain lipids. Linolenate was undetectable in brain lipids from any dietary treatments. The levels of eicosapentaenoic acid (20:5 omega 3) in groups receiving dietary 18:3 omega 3 were not different from that of the group receiving no 18:3 omega 3. These results indicate that, in the brain, 18:3 omega 3 is rapidly converted mainly to 22:6 omega 3 without being accumulated and imply that dietary 18:3 omega 3 can modulate the level of precursor of diene prostaglandins (PG) but not that of triene PG in the rat brain.

Effects of estradiol and environmental temperature changes on rat liver delta 6 microsomal desaturase activity.

The regulation of delta 6 desaturase activity by environmental temperature changes was studied in the microsomal membranes from female and ovariectomized female rat liver. Female rats adapted at 30-32 C for 20-25 days and then shifted to 13-15 C for 5 days showed an increased delta 6 desaturase system. Ovariectomized rats adapted under the same conditions did not show significant changes in this enzyme. The fatty acid compositions of microsomal phosphatidylcholine showed a decrease in arachidonic acid in female rats at 30 C compared to females at 15 C and ovariectomized rats at both temperatures. These results suggest that a modification of ovaric sex hormone levels might be responsible for the different delta 6 desaturase activity in female rats acclimated at both temperatures. In this regard, serum estradiol radioimmunoassay yielded slight differences between the two groups of female rats, suggesting that estradiol could play a role in the regulation of the delta 6 desaturase. The administration of a pharmacological dose of 17-beta estradiol to female and ovariectomized rats kept at 30 and 15 C decreased the delta 6 microsomal desaturase activity. These data suggest that estradiol levels are involved in the regulation of the delta 6 desaturase during cold adaptation.

Hemolysis and membrane lipid changes induced by xanthine oxidase in vitamin E deficient red cells

A procedure to induce homolysis by the hypoxanthine-xanthine oxidase reaction was developed and applied to vitamin E deficient red blood cells (RBCs) in rats. The reaction system was as follows: 0. 16 mM hypoxanthine, 0.05 U/ml xanthine oxidase in 2.5% RBC suspensions with an isotonic buffer (pH 7.4) containing 10 mM phosphate buffer and 125 mM saline (227 mOsm). Hemolysis was observed to depend on the vitamin E concentrations in the RBCs. Hemolysis was inhibited by catalase but not by SOD. After the reaction with vitamin E deficient RBCs, an increase in TBARS in the aqueous phase of the reaction mixture was observed. This accompanied the increase in fluorescent substances in the lipid extracts, in associatioon with a significant decrease in the PE and PS of the RBCs, and a decrease in arachidonic acid in membrane lipids. The above changes were almost completely inhibited by tocopherol incorporated into vitamin E deficient RBCs.

Dietary fish oil prevents dexamethasone induced hypertension in the rat.

This study was designed to examine the effect of dexamethasone treatment on tissue and urinary prostanoids, and to determine whether inhibition of prostaglandin biosynthesis by manipulation of dietary fatty acids accelerates the development of glucocorticoid hypertension. Forty-eight rats were placed on either a 2-series prostaglandin 'inhibitory' diet (cod liver oil/linseed oil) or a control diet of saturated fat for an initial period of 4 weeks. The groups were then divided into two so that half of each received dexamethasone in their drinking water (2.5 mg/l) for 1 week whilst continuing their respective dietary regimens. Rats on the cod liver oil diet incorporated eicosapentaenoic acid into tissue stores with a corresponding decrease in arachidonic acid, and significantly impaired ability to generate serum thromboxane B2 (33%), aortic 6-oxo-prostaglandin F1 alpha (44%), renal homogenate prostaglandin E2 (45%) and 6-oxo-prostaglandin F1 alpha (74%) and urinary prostaglandin E2 (84%) and 6-oxo-prostaglandin F1 alpha (79%). Despite the diminished levels of vasodilator 2-series prostaglandins, the cod liver oil diet prevented the development of glucocorticoid induced hypertension. Relative to their respective dietary controls, dexamethasone treatment resulted in decreased serum thromboxane B2 (20%) but increased aortic 6-oxo-prostaglandin F1 alpha (186%), renal homogenate prostaglandins (127-230%) and urinary excretion of prostaglandin E2 (640-860%) and 6-oxo-prostaglandin F1 alpha (230-365%) in both dietary groups. It therefore seems unlikely that glucocorticoid induced hypertension is a consequence of inhibition of vasodilator prostaglandin synthesis.

Changes in prostanoid synthesis in response to diet and hypertension in one-kidney, one clip rats.

This study was designed to examine the effects of diets that alter prostaglandin biosynthesis on the blood pressure in one-kidney, one clip rats with established hypertension and to compare the prostanoid generating capacity of hypertensive animals with those that remained normotensive. Rats attaining blood pressures of at least 180 mm Hg within 8 weeks of nephrectomy and renal artery stenosis were paired by weight and blood pressure and then placed on either a safflower oil or a prostaglandin I2 inhibitory diet (cod liver oil-linseed oil mix) for 4 weeks. Animals with blood pressures of less than 150 mm Hg were also paired for the same two dietary regimens. Comparison between the two blood pressure groups revealed that on both dietary regimens hypertensive rats produced significantly more aortic 6-keto-prostaglandin F1 alpha and serum thromboxane B2. Rats on the cod liver oil-linseed oil diet incorporated eicosapentaenoic acid into tissue stores with a corresponding decrease in arachidonic acid and significantly impaired ability to generate serum thromboxane B2 (36%), aortic 6-keto-prostaglandin F1 alpha (65%), renal homogenate 6-keto-prostaglandin F1 alpha (64%) and prostaglandin E2 (58%), and urinary prostaglandin E2 (70%) and 6-keto-prostaglandin F1 alpha (52%). Despite these differences in prostanoid synthesizing capacity, no differences in blood pressure were observed between the safflower oil-fed rats and rats fed cod liver oil-linseed oil within either the hypertensive or normotensive groups. These results suggest that prostanoids do not play a major role in maintaining blood pressure in established one-kidney, one clip hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatty Acid Changes in Plasma Lipids and Lymphocyte Phospholipids after Infusion of Intralipid to Newborn Infants

The fatty acid composition of the major plasma lipids and blood lymphocyte phospholipids was studied in four patients before and after 1 month of parenteral nutrition including 2 to 3 g/kg/day of Intralipid fat and in four matched controls before and after 1 month of breast-feeding. After treatment with Intralipid the concentration of polyunsaturated fatty acids including linoleic acid increased in all plasma lipids. The total concentration of polyunsaturated fatty acids in lymphocyte phospholipids did not change. The increase of linoleic acid and decrease of arachidonic acid in lymphocyte phospholipids were not statistically significant. In control infants the concentration of polyunsaturated fatty acids including linoleic and arachidonic acid in lymphocyte phospholipids increased after 1 month of breast-feeding to almost the same values as in the patients. The study indicates that at least in lymphocytes the incorporation of polyunsaturated fatty acids is actively regulated. The present way of administering Intralipid does not seem to cause any abnormal fatty acid pattern of the plasma and lymphocyte lipids. The use of intravenous fat emulsion with high content of linoleic acid in term newborns should thus not be expected to result in changes of the physical-chemical properties of membranes and membrane dysfunction.

Increased 5′ nucleotidase activity in plasma membranes from rat liver following ingestion of fish oil

The effect of n-3 fatty acid enriched diets on the membrane compositions of rat liver was studied. Sprague Dawley rats maintained on 10% menhaden oil enriched diet showed two to four fold increase in n-3 fatty acid levels and a 35% decrease in arachidonic acid in liver plasma membrane phospholipids. The specific activity of 5′-nucleotidase enzyme in n-3 fatty acid enriched membranes was two times higher than in liver membranes from control rats. These studies indicate that dietary n-3 fatty acids are incorporated into membrane lipids and influences the membrane associated enzyme activity.

Increased sensitivity of aged erythrocytes to drugs and age-related loss of cell components.

Human erythrocytes were separated into fractions of different age by centrifugation. The effect of some drugs on the separated cells, the levels of some components and enzymes in the cells and the fatty acid composition of membrane phospholipids were estimated to obtain insight into the lifespan of the cells. The bottom (old) cells were relatively more sensitive to the drugs, and aged cells pretreated with chlorpromazine had an increased osmotic fragility and increased viscous properties compared with the top (young) cells, although the differences were relatively small. Significantly lower levels of antioxidant, glutathione and tocopherol, and decreased activities of enzymes (superoxide dismutase, glutathione peroxidase and catalase) involved in peroxide metabolism were observed in old cells as compared with young ones. The proportion of arachidonic acid and the unsaturated/saturated ratio of fatty acids of phospholipids in old cells were significantly lower than those of young cells. The treatment of cells with hydrogen peroxide in vitro produced a dramatic decrease in the proportions of polyenoic fatty acids in all cell fractions, although the decrease in arachidonic acid was less in old cells. The causal relationships among these changes and the lifespan of erythrocytes are discussed.

The effect of vitamin E deficiency on some erythrocyte membrane properties.

The erythrocytes from the vitamin E-deficient rats showed no changes in comparison with the erythrocytes from the vitamin E-supplemented rats in lipid peroxides, membrane fluidity, lipid composition, and activities of defensive enzymes against the lipid peroxide formation. Once erythrocytes from vitamin E-deficient rats were exposed to H2O2, the erythrocyte membrane fluidity was significantly reduced, which was presumed to be accompanied by an increase in the hemolysis and lipid peroxide formation. Large decreases in arachidonic acid and phospholipid were also observed. These findings suggest that the reduced membrane fluidity is due to the loss of phospholipid from the erythrocytes, and raises the possibility that the reduced fluidity might contribute to the peroxidative hemolysis of the vitamin E-deficient rat erythrocytes.

Reduction in thromboxane formation by n-3 fatty acids enriched lung microsomes from rat and guinea pig following the ingestion of dietary menhaden oil

Feeding rats and guinea pigs on a diet containing 5% menhaden oil altered the fatty acid composition of lung microsomes. The lung microsomal phospholipids contained increased amounts of n-3 fatty acids, eicosapentaenoic (20:5) and docosahexaenoic acid (20:6), following the ingestion of menhaden oil. There was a concomitant decrease in arachidonic acid (20:4) levels in rat lung microsomes, but no significant change of this fatty acid was observed in the microsomes from guinea pigs. The ability of lung microsomes to convert 14C-arachidonic acid. into thromboxane (TXB) was reduced by the enrichment of n-3 fatty acids in the microsomal lipids.

Decreased cytochrome oxidase activity in hepatic mitochondria after chronic ethanol consumption and the possible role of decreased cytochrome aa3 content and changes in phospholipids.

In ethanol-fed baboons, hepatic mitochondrial cytochrome oxidase activity and cytochrome aa3 content were significantly decreased by 58.3 and 50.5%, respectively, compared to their pair-fed controls. However, there was no significant correlation between the two, suggesting that other factors in addition to cytochrome aa3 may be responsible for the depression in cytochrome oxidase activity. The total phospholipid content of the mitochondrial membranes was significantly decreased (0.24 +/- 0.03 mumol of phospholipid phosphorus/mg of protein vs. 0.32 +/- 0.04 in controls). This change was accounted for, in part, by the significant decrease in the levels of phosphatidylcholine and cardiolipin. In addition, the fatty acid pattern of the phospholipids was changed. There was a marked increase in the relative amounts of oleic and linoleic acids and a decrease in arachidonic acid. These changes were associated with an increase in the activity of phospholipase A2. The reactivation rate of phospholipid-depleted cytochrome oxidase by endogenous phospholipids from ethanol-fed baboons was significantly lower than that by phospholipid from pair-fed controls, when measured at an optimal phospholipid to protein ratio. Thus, it appears that alterations in the phospholipid composition of the mitochondrial membranes are responsible, at least in part, for the depression of cytochrome oxidase activity produced by chronic ethanol consumption.

The phospholipids of the hepatic endoplasmic reticulum. Structural change in liver injury.

Endoplasmic-reticulum phospholipids were measured during the first hour after carbon tetrachloride administration to male Sprague-Dawley rats and compared with carbon tetrachloride challenge of microsomes from control animals in vitro. The extracted lipids were separated by high-pressure liquid chromatography. No significant differences in the abundance of phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol or phosphatidylcholine were found after either treatment when compared with untreated controls. Diene conjugate formation in each separated phospholipid was determined by measuring A(232) and expressed on the basis of lipid phosphorus. Phosphatidylserine was peroxidized 6-fold greater than in controls after challenge in vivo, reaching maximal change after 15min, whereas the other phospholipids showed little or no alteration. Fatty acid composition analysis was performed by g.l.c. after transesterification of individual phospholipids. Phosphatidylserine revealed two types of response: an abrupt decrease in relative abundance of oleic acid (C(18:1)) and linoleic acid (C(18:2)) without further loss and a slower, linear decrease in arachidonic acid (C(20:4)) over the first hour. Similar changes were not seen in other phospholipids. In the ;in vitro' model, the relative amounts of the phospholipids do not change. The extent of peroxidation was greater in all the phospholipids than found in vivo, with phosphatidylserine peroxidized to the greatest extent. These data suggest that carbon tetrachloride injury in vivo produces an early peroxidative event and that a specific phospholipid (phosphatidylserine) is selectively modified, although maintaining its relative concentration in the membrane. Dissection of this process in vitro will require refinement of existing systems to reduce the non-specific changes associated with the model system.

Utilization of arachidonic and linoleic acids by cultured human endothelial cells.

When cultured human umbilical vein endothelial cells are supplemented with linoleic acid, the arachidonic acid content of the cellular phospholipids is reduced approximately 35%. Most of the fatty acid compositional change occurs during the first 24 h. One factor responsible for this effect is the inability of the endothelial cells to convert appreciable amounts of linoleic to arachidonic acid, due to a fatty acid delta 6-desaturase deficiency. By contrast, these endothelial cultures contain delta 5- and delta 9-desaturase activity and are able to elongate long-chain polyunsaturated fatty acids. The other factor that contributes to the decrease in arachidonic acid is that high concentrations of linoleic acid reduce the incorporation of arachidonate into cellular phospholipids. Stearic acid, a long-chain saturate, does not produce any reduction, whereas eicosatrienoic acid is an even more effective inhibitor than linoleic acid. In spite of the fact that high concentrations of these polyunsaturates produced inhibition, the endothelial cells were found to efficiently incorporate exogenous arachidonic acid into cellular phospholipids and triglycerides. This may serve to compensate for the inability of these cells to synthesize arachidonic acid from linoleic acid. These findings suggest that the endothelium obtains arachidonic acid from an extracellular source, that this cannot be provided in the form of linoleic acid and, in fact, that high concentrations of linoleic acid actually may interfere with the ability of the endothelium to maintain an adequate supply of intracellular arachidonic acid.

Fatty acid pattern of the erythrocyte lipids and plasma vitamin E in the first days of life.

The plasma level of vitamin E is lower in newborns than in adults. The fatty acid composition of the erythrocyte lipids changes during the first weeks of life, the major changes being the increase of linoleic acid and the decrease of arachidonic acid. These changes cannot be ascribed to variation of erythrocytes age, but they seem to be related to variations in the fatty acid pattern of the major lipid fractions of plasma. The lowest ratio between vitamin E in plasma and the percentage of polyunsaturated fatty acids in erythrocyte membrane is reached in the first few days following the beginning of feeding. The results are discussed in relation to the development of hemolysis during the first days of life.

Loss of essential membrane lipids and ascorbic acid from rat brain following cryogenic injury and protection by methylprednisolone.

Previous work has shown that unsaturated fatty acid components of model membrane phospholipids in vitro, damaged via a free radical mechanism, are protected by the presence of cholesterol in these membranes. The participation of these membrane lipids in the pathogenesis of traumatic injury to brain was studied in vivo using the Klatzo method of cryogenic injury in rats. Increased edema 4 hr after cryogenic injury was noted on the lesioned side. Total cerebral cholesterol was decreased significantly in the lesioned hemispheres 10 hr following injury. In lesioned animals pretreated and post-treated with methylprednisolone, there were no significant differences in the cholesterol levels. Arachidonic acid isolated from total membrane phospholipids was significantly reduced on the injured side 24 hr after injury, but not before. Other fatty acids were not significantly affected. Methylprednisolone treatment prevented the decrease in arachidonic acid. Animals that had received a cold injury had significant decreases in ascorbic acid levels after 4 hr on the lesioned side of the brain. This decrease was significantly ameliorated by corticosteroid administration. These results support the hypothesis that the protective effect of corticosteroids in cryogenic cerebral trauma may be due to antioxidant protection of major cell membrane lipid components such as cholesterol and phospholipids.

Cytochrome P-450 lowering effect of alkyl halides, correlation with decrease in arachidonic acid

Treatment of male rats with carbon tetrachloride, bromotrichloromethane, chloroform, 1,2-dibromoethane, 1-bromo-2-chloroethane, and 1,2-dibromo-3-chloropropane results in a decrease in cytochrome P-450 content and alterations in the relative content of fatty acids in hepatic microsomes. A high correlation was found between the loss of cytochrome P-450, the decrease in arachidonic acid (r=0.93), and the increases in linoleic (r=−0.91) and oleic acids (r=−0.89).

Lipids of whole cells and plasma membrane fractions from Balb/c3T3, SV3T3, and concanavalin A-selected revertant cells.

The lipid composition of Balb/c3T3, SV3T3, and the concanavalin A-selected SV3T3 revertant cells has been analyzed at the whole cell and plasma membrane levels. In comparison to untransformed 3T3 whole cells, SV3T3 cells showed an unchanged content of triacylglycerols, free fatty acids, and glycerylether diesters but a lower concentration of total phospholipids, while no significant difference was found in the phospholipid composition. Whole SV3T3 revertant cells exhibited a lipid composition similar to that in untransformed 3T3 cells with the exception of a higher proportion of sphingomyelin. Analysis of isolated plasma membranes did not reveal any significant differences in the cholesterol to phospholipid molar ratio between 3T3 and SV3T3 or SV3T3 revertant cells. The major changes in the acyl chain pattern SV3T3 compared with whole 3T3 cells consisted of an increase of oleic and palmitoleic acids coupled with a decrease of C20 and C22 polyunsaturated acids in phosphatidylethanolamine and phosphatidylcholine; an increase of oleic acid was also evident in SV3T3 phosphatidylinositol plus phosphatidylserine. An increase of palmitoleic and oleic acids together with a decrease of arachidonic acid was also found in phosphatidylethanolamine of SV3T3 plasma membranes; the only change in SV3T3 plasma membrane phosphatidylcholine was an increase of oleic acid. An increase of monoenoic acids together with a decrease of arachidonic acid was also found in phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol plus phosphatidylserine of SV3T3 revertant cells at the level of both whole cells and plasma membranes.

The fatty acid pattern of triglycerides and FFA in serum of spontaneously hypertensive rats (SHR)

The fatty acid patterns of serum triglycerides and FFA in SHR and in normotensive controls aged 4, 8 and 26 weeks were estimated by gas-liquid chromatography. In serum triglycerides of SHR, the percentage of linoleic acid (C 18:2) was lower and the content of arachidonic acid (C 20:4) higher than in age-matched control animals. A continuous increase in palmitic (C 16) and linoleic acids as well as a decrease in arachidonic acid has been found with advancing age, the most striking differences existing between 4- and 8-week-old animals, i.e. before onset of arterial hypertension in SHR. In the pre-hypertensive stage, the percentage of arachidonic acid was about 3 times as high as in later stages in SHR. This gradation was, however, even more pronounced in normotensive control rats. The C 18:2 C 20:4 - ratio of triglycerides was lower in SHR but increased with age in both groups reaching a 5–8-fold level. Similar behavior of the FFA fatty acid pattern was less marked. Alterations in levels of linoleic and arachidonic acids are of interest because of their pathogenic role as precursors of prostaglandins in the development of genetically spontaneous hypertension in rats. The results are discussed in connection with the hypotensive effect of a linoleic acid-rich diet recently reported in hypertensive rats.