Arachidonic Acid In Phosphatidylcholine Research Articles

Circulating Marine and Vegetable Omega-3 at the Time of ST-Segment Elevation Myocardial Infarction and Incident Hard Clinical Endpoints

Abstract Objectives Dietary marine omega-3 eicosapentaenoic acid (EPA) is readily incorporated into cardiac cell membranes, partially replacing the omega-6 arachidonic acid (AA). Blood omega-3 is an objective marker of their intake over the last days. Increasing blood EPA at the time of a ST-segment elevation myocardial infarction (STEMI) relates to a smaller infarct size and preserved long-term left ventricular ejection fraction. We explored whether blood EPA at the time of STEMI also relates to a lower incidence of hard clinical endpoints. We also explored whether blood alpha-linolenic acid (ALA, the vegetable omega-3) modulates such association. Methods We prospectively included 944 consecutive patients treated with primary percutaneous coronary intervention in a single tertiary referral hospital. We determined fatty acids in serum phosphatidylcholine (PC) at 12 hours of evolution. The primary outcomes were cardiovascular disease-related hospital readmission and all-cause mortality after 3 years of follow-up. We constructed multivariable Cox proportional hazards models, calculating risk estimates as hazard ratios (HR). Results The mean age of the cohort was 61 years and 209 (22.1%) were women. During follow-up, 130 patients (13.8%) were readmitted for cardiovascular disease, and 108 (11.4%) died. After adjustment for known clinical predictors, multivariate analysis showed that EPA in serum PC at the time of STEMI inversely related to incident hospital readmission (HR, 0.74; 95% CI, 0.56–0.96; P = 0.024, for a 1 SD increase). Further adjustment for serum PC AA and ALA did not change the association. EPA in serum PC was found to be unrelated to 3-y total mortality. However, after including serum PC proportions of AA and ALA into the model, we observed a significantly decreased risk of mortality for ALA (HR, 0.65; 95% CI, 0.44–0.96; P = 0.030, for a 1 SD increase). Conclusions Increasing proportions of EPA and ALA in serum PC at the time of STEMI inversely relate to 3-y cardiovascular disease-hospital readmission and all-cause mortality, respectively. Dietary EPA and ALA act synergistically and are partners rather than competitors in improving prognosis in case of a STEMI. Funding Sources Instituto de Salud Carlos III, Spain; California Walnut Commission.

Biomarkers of Docosahexaenoic Acid but Not Arachidonic Acid Reflect Dietary Intakes in Toddlers at Ages 1 and 2 Years Who Are Not Meeting Dietary Recommendations

Background:Long-chain n–6 and n–3 PUFAs are important for growth and development. However, little is known about requirements and current dietary intakes of these fatty acids in toddlers. Objectives:This study assessed dietary intakes of n–6 and n–3 PUFAs and determined the relation to circulating PUFAs in toddlers at ages 1 and 2 y. Methods:This is a secondary analysis of data from toddlers enrolled in a double-blind randomized controlled trial of arachidonic acid (ARA) and DHA supplementation between ages 1 and 2 y. Dietary intakes of fatty acids were estimated by 3-d food records, and fatty acid composition in plasma total phospholipids, red blood cell phosphatidylethanolamine (PE), and phosphatidylcholine (PC) were assessed by GC at baseline in all subjects (n = 110; mean age 1.12 y; 64% male) and in the control subjects at 2 y (n = 43). Methods:The dietary intakes of ARA, EPA, and DHA at age 1 y (baseline) were [mean (median)] 36.8 (30.0), 16.0 (0.00), and 31.1 (10.0) mg/d, respectively. Dietary intakes increased to 52.7 (45.0), 35.8 (0.00), and 64.8 (20.0) mg/d, respectively, at age 2 y (P < 0.05). The predominant dietary source of EPA and DHA was fish/seafood; eggs were an important source of ARA and DHA. Dietary DHA intakes were positively associated with plasma PE and PC DHA (P < 0.05). No relations between dietary ARA intakes and plasma PE and PC ARA (P > 0.05) were observed. Conclusions:These findings suggest that most toddlers are not meeting the recommendation for dietary PUFA intakes and that higher dietary DHA intakes are reflected in plasma PE and PC DHA composition. Further work is required to investigate a biomarker for dietary ARA intake. This trial is registered at clinicaltrials.gov as NCT01263912.

Different intakes of n-3 fatty acids among pregnant women in 3 regions of China with contrasting dietary patterns are reflected in maternal but not in umbilical erythrocyte phosphatidylcholine fatty acid composition

There is limited information regarding the intake and status of polyunsaturated fatty acids (PUFA) in Chinese pregnant women with different dietary patterns. We hypothesize that there will be significant differences in long chain n-3 and n-6 PUFA status in pregnant women from 3 regions of China (river/lake, coastal and inland). Dietary fatty acid intakes and fatty acid profiles in maternal and umbilical erythrocyte phosphatidylcholine (PC) were analyzed. The median daily intakes (mg) of eicosapentanoic acid and docosahexaenoic acid (DHA) in the coastal group (64.6 and 93.9, n = 42) were significantly higher than those in the river/lake group (27.9 and 41.8, n = 41) and the inland group (12.1 and 41.1, n = 40). Daily intake of arachidonic acid (AA) was highest (170.2 mg) in the inland group. The median DHA level (%) of maternal erythrocyte PC was comparable between river/lake and inland groups (5.7 vs. 5.6) while both were significantly lower than in coastal group (8.4). The median AA level (%) of maternal erythrocyte PC tended to be lower in the coastal group than in the inland group but the difference was not significant. The AA and DHA levels in umbilical erythrocyte PC were comparable among the 3 groups. In conclusion, differences in long chain n-3 PUFA intake between geographic regions, in particular in DHA, were reflected in differences in maternal erythrocyte PC DHA status but did not result in differences in umbilical erythrocyte PC.

The Polyunsaturated Fatty Acid Composition of Hepatic and Plasma Lipids Differ by Both Sex and Dietary Fat Intake in Rats1–3

In rats and humans, females have higher liver and/or plasma docosahexaenoic acid (DHA) content than males. We hypothesized that the effect of variation in total fat or essential fatty acid intakes on liver and plasma fatty acid composition would differ between sexes. Rats were fed a low-fat soybean oil (LFS), high-fat soybean oil (HFS), or high-fat linseed oil (HFL) diet for 20 d. There were significant sex differences in LFS rats in proportions of (n-3) and (n-6) fatty acids in plasma and liver contingent on lipid class. Significant diet × sex interactions were observed for eicosapentaenoic acid (EPA), DHA, and arachidonic acid (AA) status. HFL females had a higher proportion of EPA in plasma and liver phosphatidylcholine (PC), DHA in liver triacylglycerol (TAG), and AA in plasma PC than HFS and LFS females. These findings show that the effect of varying dietary fat intake on (n-3) and (n-6) long-chain PUFA (LCPUFA) status is modified by sex. Liver phospholipid and TAG fatty acid product:substrate ratios suggested greater Δ6 desaturase (Δ6D) activity in females than in males. The HFL diet induced higher Δ6D mRNA expression compared with the LFS or HFS diets and HFL females had 10% higher expression of Δ6D mRNA than HFL males. Together, these findings show that sex is an important determinant of the effect of variations in fat and fatty acid intake on LCPUFA status, which may have implications for recommendations for fat and fatty acid intake in humans.

Lipid peroxidation in brain during aging in the senescence-accelerated mouse (SAM)

Accumulation of toxic amyloid-β (Aβ)-peptide is suggested to cause oxidative stress in Alzheimer's disease (AD) brain, and decrease the content of polyunsaturated fatty acids (PUFA) in neuronal membrane lipids. The senescence accelerated prone mice (SAMP8) have age-related increases in the level of hippocampal Aβ-peptide, learning and memory deficits, and a shorter lifespan than their controls. The effects of age-related oxidative damage on PUFA content in membrane phospholipids (PL), and α-tocopherol concentration were investigated in hippocampus and amygdala of 2-, 4-, 12-, and 18-month-old SAMP8 mice. In comparison to the younger SAMP8 mice, the hippocampus of the 12-month-old mice contained lower proportions of docosahexaenoic acid (DHA) in phosphatidylserine (PS) and phosphatidylinositol (PI), and higher proportions of arachidonic acid (AA) in PS. Their amygdala contained a lower proportion of AA in phosphatidylcholine (PC). In the hippocampus of the oldest age group, the proportions of DHA in PS, and AA in PC and PI were higher than in the younger age groups. At 2 months of age, the amygdala contained a higher concentration of α-tocopherol than the hippocampus, but this difference between the two brain regions was lost with aging. The oldest age group contained the highest concentration of α-tocopherol, indicating a protection against oxidative damage of PUFA in brain membrane phospholipids.

Effects of long-term feeding of marine oils with different positional distribution of eicosapentaenoic and docosahexaenoic acids on lipid metabolism, eicosanoid production, and platelet aggregation in hypercholesterolemic rats.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were distributed mainly in the sn-1,3 positions of seal oil triglyceride and in the sn-2 position of squid oil triglyceride. Seal oil-rich or squid oil-rich fats having constant saturated/monounsaturated/polyunsaturated fatty acid (PUFA) and n-6/n-3 PUFA ratios were fed to exogenously hypercholesterolemic rats for 1 60 d. The control fat contained linoleic acid as the sole PUFA. Before starting the experimental diets, rats were orally treated with high doses of vitamin D for 4 d to accelerate atherogenesis. The percentage of arachidonic acid in phosphatidylcholine and phosphatidylethanolamine of liver, platelets, and aorta was lower in the marine oil groups than in the control group, seal oil being more effective than squid oil. Maximal platelet aggregation induced by collagen was significantly lower in both marine oil groups. Platelet thromboxane (TX) A2 production induced by collagen or thrombin was markedly reduced by feeding seal or squid oils, the reduction being more pronounced in the seal oil than in the squid oil group. Aortic prostacyclin (PGI2) production was the same among the three groups. The ratio of the productions of aortic PGI2 and platelet TXA2 was significantly higher in the seal oil than in the control group. Although there was no difference in intimal thickness among the three groups, the aortic cholesterol content was significantly lower in the marine oil groups than in the control group. These results showed that the main effects in rats of the different intramolecular distributions of EPA and DHA in dietary fats were on arachidonic acid content in tissue phospholipids and on platelet TXA2 production.

Platelet-activating factor preferentially stimulates the phospholipase A2/cyclooxygenase cascade in the rabbit cornea.

Platelet-activating factor (PAF) is formed in the cornea after injury as well as by infiltrating inflammatory cells. We have studied the effects of PAF on the release and metabolism of arachidonic acid (AA) in the rabbit cornea. Corneal lipids were labeled in vivo by injecting [3H]AA and subsequently incubated in vitro with 100 nM PAF in the presence or absence of 10 microM BN50727, a PAF antagonist. The AA and eicosanoids released by incubated corneas were analyzed by high-performance liquid chromatography (HPLC). Tissue lipids were examined by mono- and bidimensional thin-layer chromatography (TLC). Within 5 min, PAF stimulated AA release to 76% above control levels. BN50727 inhibited the AA release elicited by PAF at all time points studied. The decreased content of [3H]AA in phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) following PAF exposure and the lack of stimulation by PAF on the release of [3H] linoleic acid suggest that the cytosolic phospholipase A2 was activated. PAF also stimulated depletion of AA from the inositol lipids, phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-biphosphate (PIP2) and increased content of [3H]AA into diacylglycerol (DAG) and phosphatidic acid (PA). This reaction indicates that PAF could also mediate activation of other phospholipases in the cornea. In addition, PAF preferentially stimulated the cyclooxygenase pathway. The PAF antagonist BN50727 mainly suppressed the PAF-stimulated release of PGE2. The antagonist did not inhibit lipoxygenase activity even after 30 min of PAF stimulation. These results suggest that PAF activate a phospholipase A2/cyclooxygenase pathway in the cornea via a PAF-receptor mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

5c,11c,14c-eicosatrienoic acid and 5c,11c,14c,17c-eicosatetraenoic acid of Biota orientalis seed oil affect lipid metabolism in the rat.

The effects of 5c,11c,14c-eicosatrienoic acid (20:3BSO) and 5c,11c,14c,17c-eicosatetraenoic acid (20:4BSO), polyunsaturated fatty acids (PUFA) contained in Biota orientalis seed oil (BSO), on lipid metabolism in rats were compared to the effects of fats rich in linoleic acid (LA) or alpha-linolenic acid (ALA) under similar conditions. The potential effect of ethyl 20:4BSO as an essential fatty acid also was examined in comparison with the ethyl esters of LA, ALA and gamma-linolenic acid (GLA). BSO- and ALA-rich fat decreased the concentration of plasma total cholesterol, high density lipoprotein cholesterol, triglyceride and phospholipid as compared to LA-rich fat. BSO was more effective in reducing plasma cholesterol concentrations than was the ALA-rich fat. Dietary BSO markedly decreased the hepatic triglyceride concentration as compared to the LA-rich or ALA-rich fats. Aortic production of prostaglandin I2 tended to decrease in rats fed BSO or ALA-rich fat compared to those fed the LA-rich fat. Adenosine diphosphate-induced platelet aggregation was similar in the three groups. The proportion of arachidonic acid (AA) in liver phosphatidylcholine (PC) of rats fed BSO was lowest compared to that of rats fed ALA-rich or LA-rich fats. Administration of 20:4BSO, ALA or GLA to essential fatty acid-deficient rats decreased the ratio of 20:3n-9 to AA in liver PC to the same extent; administration of LA was more effective. The results indicate that the effects of specific PUFA contained in BSO on lipid metabolism are different from those of LA and ALA. It is also suggested that 20:4BSO may exhibit some essential fatty acid effects.

Phospholipid Metabolism in Platelets from Stroke-Prone Spontaneously Hypertensive Rats and Wistar Kyoto Rats.

Platelets from stroke-prone spontaneously hypertensive rats (SHRSP) show severe hypofunctions accompanied by defective protein (P47) phosphorylation. To examine the mechanism of platelet hypofunctions, phospholipid metabolism in SHRSP was compared with that in Wistar Kyoto rats (WKY). Phosphatidylinositol (PI) content was 20% less in SHRSP than in WKY, but no changes were observed in other phospholipids. Incorporation of [3H]-arachidonic acid (AA) into PI and phosphatidylethanolamine (PE) was 12% and 11% lower, and that into phosphatidylcholine (PC) was 6% higher in SHRSP than in WKY. Thrombin-induced diacylglycerol and phosphatidic acid formation were similar in both groups of platelets. Thrombin-induced release of [14C]-AA from the labeled platelets and its metabolism to eicosanoids occurred at similar rates. These results suggest that reduced formation of diacylglycerol, an activator of protein kinase C (PKC), does not cause defective phosphorylation of P47, a substrate of PKC, in SHRSP. However it remains unclear how the lower PI content and the altered distribution of AA in PC and PE is related to SHRSP platelet hypofunctions.

Abnormalities in Epidermal Lipid Metabolism in Patients with Atopic Dermatitis

Atopic dermatitis is an inflammatory skin disease characterized by dryness and itch of the skin. In this study, we measured the phospholipid content and the fatty acid pattern of lesional and lesion-free epidermal keratome biopsies on 15 patients. For comparison, epidermal biopsies were obtained from healthy individuals undergoing plastic surgery. The phospholipid content of atopic epidermis was nearly twice as high as in healthy epidermis. Monounsaturated fatty acids in the phosphoglycerides were significantly increased (p less than 0.001) and n-6 fatty acids were significantly decreased (p less than 0.001) in lesional atopic epidermis compared to lesion-free epidermis. The content of esterified arachidonic acid in phosphatidylcholine from lesional epidermis was only 49% of that found in healthy epidermis (p less than 0.001). The content of free arachidonic acid was 47% higher (p less than 0.05), whereas the content of free long-chain saturated fatty acids was decreased by 29% (p less than 0.01), in lesional compared to lesion-free atopic epidermis. The disease severity, calculated as an arbitrary index, correlated inversely with the n-6 fatty acid content of lesion-free atopic epidermis (r = -0.89, p less than 0.001). Our findings suggest that atopic epidermis is characterized by an increased activity of phospholipase A2 and an incomplete transformation of phospholipids into other lipid classes.

Dietary n-9, n-6 and n-3 fatty acids modify linoleic acid more than arachidonic acid levels in plasma and platelet lipids and minimally affect platelet thromboxane formation in the rabbit

We have studied the effects of semisynthetic diets containing 5% by weight (12% of the energy) of either olive oil (70% oleic acid, OA) or corn oil (58% linoleic acid), or fish oil (Max EPA, containing about 30% eicosapentaenoic, EPA C 20:5 n-3, plus docosahexaenoic, DHA C 22:6 n-3, acids, and less than 2% linoleic acid), fed to male rabbits for a period of five weeks, on plasma and platelet fatty acids and platelet thromboxane formation. Aim of the study was to quantitate the absolute changes of n-6 and n-3 fatty acid levels in plasma and platelet lipid pools after dietary manipulations and to correlate the effects on eicosanoid-precursor fatty acids with those on platelet thromboxane formation. The major differences were found when comparing the group fed fish oil and depleted linoleic acid vs the other groups. The accumulation of n-3 fatty acids in various lipid classes was associated with modifications in the distribution of linoleic acid and arachidonic acid in different lipid pools. In platelets maximal incorporation of n-3 fatty acids occurred in phosphatidyl ethanolamine, which also participated in most of the total arachidonic acid reduction occurring in platelets, and linoleic acid, more than archidonic acid, was replaced by n-3 fatty acids in various phospholipids. The archidonic acid content of phosphatidyl choline was unaffected and that of phosphatidyl inositol only marginally reduced. Thromboxane formation by thrombin stimulated platelets did not differ among the three groups, and this may be related to the minimal changes of arachidonic acid in phosphatidyl choline and phosphatidyl inositol.

Disparate Effects of Dietary Fatty Acids on Activity of 5′-Nucleotidase of Rat Liver Plasma Membrane

The effects of incorporation of dietary n-3 polyunsaturated fatty acids (PUFA) into rat liver plasma membrane on the activity of 5'-nucleotidase (EC 3.1.3.5) was studied. The membrane phospholipids from rats fed a diet containing 10% by weight menhaden oil (MO) for 3 wk contained more n-3 PUFA and less n-6 PUFA in phospholipids classes, i.e., 24% and 65% less linoleic and arachidonic acid in phosphatidylcholine, than in rats fed 10% coconut oil (CNO) diets. The specific activity of 5'-nucleotidase in n-3 PUFA-enriched hepatic plasma membranes was 1.6- to 2-fold higher than that in rats fed CNO or corn oil (CO). Lineweaver-Burk plots for 5'-nucleotidase in liver plasma membranes isolated from rats fed MO and CNO showed no significant differences in Km values but the Vmax was increased by 67% in MO-fed rats. Arrhenius plots showed a break point in 5'-nucleotidase activity at 28.3 degrees C and 30.8 degrees C in plasma membranes from MO- and CNO-fed rats, respectively. The implications of this in the generation of adenosine and its possible impact on physiological functions are discussed.

Effects of n-3 polyunsaturated fatty acids on coronary heart disease.

The purpose of this paper is to discuss the role of n-6 and n-3 polyunsaturated fatty acids in coronary heart disease (CHD). The level of n-6 and n-3 fatty acids in plasma and cardiac phospholipids was examined in relation to CHD in man. The fatty acid profile of cardiac phospholipids was also examined in relation to various risk factors of CHD, such as the composition of dietary fat, aging and stress. Life expectancy in Iceland is higher than in other Nordic countries, and the cardiovascular diseases mortality is lower in Iceland in the older age groups. There is a positive correlation between the level of arachidonic acid (AA) in plasma phospholipids (PL) in the normal population and cardiovascular disease mortality in Nordic countries. The level of AA in plasma PL is significantly higher in patients with CHD than in normal subjects. Dietary intake of fish or fish oil lowers cellular levels of AA and favorably influences eicosanoid metabolism in platelets and leukocytes. The roles of n-6 and n-3 fatty acids in heart muscle are less well understood. Rats fed diets containing either 10% butter, corn oil or cod liver oil showed markedly different fatty acid composition of individual phospholipids in sarcolemma. Dietary cod liver oil lowered the AA level in sarcolemmal phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) by 50% compared to butter or corn oil fed rats, replacing AA with docosahexaenoic acid (DHA). Adaptation to moderate to severe stress induced by repeated administration of catecholamines for 15 days resulted in marked but reversible alterations in the fatty acid profile of cardiac phospholipids. During severe stress the level of AA increased by 50% in PC replacing linoleic acid (LA), whereas in PE the DHA increased markedly replacing LA. Aging was accompanied by similar alterations in cardiac phospholipids, increased levels of AA in PC and increased DHA in PE. The incidence of ventricular fibrillation (VF) and sudden cardiac death induced by isoproterenol in adult rats fed different dietary fat was lowest in rats fed cod liver oil, with a low ratio of AA/DHA in cardiac phospholipids. Mortality due to VF was highest in rats fed corn oil with the highest ratio of AA/DHA. Sudden cardiac death in man was frequently associated with a higher ratio of AA/DHA than observed in people of the same age who died in accidents. The balance between n-6 and n-3 fatty acids in cellular phospholipids seems to play an important role in stress tolerance and survival.

Reversible alterations in fatty acid composition of heart muscle membrane phospholipids induced by epinephrine in rats fed different fats

The effect of epinephrine on the fatty acid composition of heart muscle phospholipids was examined in rats fed diets containing 10% by weight of butter, corn oil, or cod liver oil. Repeated administration of epinephrine caused elevation of docosahexaenoic acid in phosphatidylcholine and phosphatidylethanolamine and a corresponding decrease in linoleic acid content. Arachidonic acid was increased in phosphatidylcholine and decreased or unaltered in phosphatidylethanolamine. These alterations were qualitatively similar despite different initial levels of fatty acids due to different dietary fats. The initial level of arachidonic acid in phosphatidylcholine and phosphatidylethanolamine was more than 50% lower in the rats fed cod liver oil than in rats fed butter and was partially replaced by the (n-3) fatty acids docosahexaenoic and eicosapentaenoic acid. Dietary corn oil produced less changes in fatty acid composition than cod liver oil compared to the reference diet, 10% butter. The results demonstrate that repeated administration of epinephrine caused significant alterations in fatty acid composition of major phospholipids in heart muscle of rats fed diets enriched with either butter, corn oil, or cod liver oil.

Asymmetric distribution of arachidonic and n-3 polyunsaturated fatty acids in rat liver microsomal membranes under a fat-free diet.

Rats adapted to a corn oil or a fish oil diet were fed a fat-free diet, and changes in phospholipid polyunsaturated fatty acids (PUFA) in the inner and outer leaflets of liver microsomal membranes were followed for 18 wk. In rats previously adapted to a corn oil diet, arachidonic acid in phosphatidylcholine and phosphatidylethanolamine in the inner and outer leaflets did not decrease quickly; rather, linoleic acid decreased more than arachidonic acid for the first three weeks of feeding the fat-free diet. Even at 18 wk, 40-50% of the beginning arachidonic acid levels were still retained. In contrast, in rats previously adapted to a fish oil diet, the n-3 PUFA were quickly decreased by the fat-free diet to only 10-30% at 18 wk. Due to the appearance and increase of n-9 eicosatrienoic acid in the replacement of the n-3 and n-6 PUFA, total PUFA did not decrease in the inner and outer phosphatidylcholine in either group, but decreased somewhat in the phosphatidylethanolamine due to the insufficient increase of the n-9. On the other hand, the overall degrees of unsaturation in phosphatidylcholine fatty acids were always higher in the outer than in the inner leaflets and were not altered by feeding the fat-free diet even for 18 wk. Thus, the results appear to reveal the physiological importance of unsaturation ratio of fatty acids and the necessity of arachidonic acid in each membrane leaflet.

Hepatic microsomal phospholipids in rats exposed intratracheally to coal fly ash.

The effects of intratracheal administration of fly ash (50 mg/kg body weight, daily for 7 days) on hepatic microsomal phospholipid metabolism has been studied in rats using various phospholipid precursors, viz NaH2(32)PO4, (methyl-14C)-choline, and (methyl-14C)-methionine. Fly ash administration significantly increased microsomal phosphatidylcholine (PC), and lysophosphatidylcholine (LPC). The incorporation of NaH2(32)PO4 into total liver phospholipids, PC and Phosphatidyl ethanolamine (PE) was significantly increased in fly ash-treated rats as compared to the control. Fly ash administration also increased the incorporation of (methyl-14C)-choline into microsomal PC. Incorporation of (methyl-14C)-methionine into microsomal PC was not affected. Fly ash administration decreased the per cent distribution of arachidonic acid in PC and PE and increased that of oleic acid in PC and of linoleic acid in PE.

Inhibitory effect of prostaglandin E2, forskolin, and dibutyryl cAMP on arachidonic acid release and inositol phospholipid metabolism in guinea pig neutrophils.

The effect of prostaglandin E2 (PGE2), forskolin, and dibutyryl cAMP on arachidonic acid release, inositol phospholipid metabolism, and Ca2+ mobilization was investigated. The chemotactic tripeptide (formylmethionyl-leucyl-phenylalanine (fMLP))-induced arachidonic acid release in neutrophils was significantly inhibited by PGE2, forskolin, and dibutyryl cAMP. Among them, PGE2 was found to be the most potent inhibitor. However, when neutrophils were stimulated by Ca2+ ionophore A23187, such inhibitory effect by these agents was less marked. PGE2 also suppressed the enhanced incorporation of [32P]Pi into phosphatidic acid (PA) and phosphatidylinositol in a dose-dependent manner in fMLP-stimulated neutrophils. Also in this case, Ca2+ ionophore-induced alterations were hardly inhibited by PGE2. As well, PGE2 inhibited the fMLP-induced decrease of [3H]arachidonic acid in phosphatidylcholine and phosphatidylinositol and the increase in PA very significantly. But the inhibitory effect by PGE2 was found to be weak in Ca2+ ionophore-stimulated neutrophils. These results suggest that a certain step from receptor activation to Ca2+ influx is mainly inhibited by PGE2. Concerning polyphosphoinositide breakdown, PGE2 did not affect the fMLP-induced decrease of [32P]phosphatidylinositol 4,5-bisphosphate which occurred within 10 s but inhibited the subsequent loss of [32P]phosphatidylinositol 4-phosphate and [32P]phosphatidylinositol, suggesting that the compensatory resynthesis of phosphatidylinositol 4,5-bisphosphate was inhibited. On the other hand, fMLP-induced diacylglycerol formation was suppressed for the early period until 1 min, but with further incubation, diacylglycerol formation was rather accelerated by PGE2. Moreover, the inhibition of PA formation by PGE2 became evident after a 30-s time lag, suggesting that the conversion of diacylglycerol to PA is inhibited by PGE2. The formation of water-soluble products of inositol phospholipid degradation by phospholipase C, such as inositol phosphate, inositol 1,4-bisphosphate, and inositol 1,4,5-trisphosphate, was also suppressed by PGE2 treatment. However, the inhibition was not so marked as that of arachidonic acid release and PA formation. Thus, PGE2 appeared to inhibit not only initial events such as polyphosphoinositide breakdown but also turnover of inositol phospholipids. PGE2, forskolin, and dibutyryl cAMP did not block the rapid elevation of intracellular Ca2+ which was observed within 10 s in fMLP-stimulated neutrophils. However, subsequent increase in intracellular Ca2+ which was caused from 10 s to 3 min after stimulation was inhibited by PGE2, forskolin, and dibutyryl cAMP.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence Supporting a Correlation between Arachidonic Acid Release and Prolactin Secretion from GH3Cells*

In this study, pharmacological agents that alter phospholipase A2 activity were examined for their effects on PRL release and arachidonic acid mobilization in GH3 cells, a pituitary tumor cell line. Stimulators of phospholipase A2 activity, melittin and mastoparan, increased PRL release during short term incubation. This stimulation was reduced by carbachol, a cholinergic receptor ligand that inhibits PRL release from GH3 cells. Melittin also caused release of [3H]arachidonic acid that had previously been incorporated into phospholipids. Increased levels of free [3H]arachidonic acid in the medium were associated with a loss of radiolabel from the phospholipid fraction of the cells. The [3H]arachidonic acid in phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol was reduced during melittin exposure. In contrast, two inhibitors of phospholipase A2, dibromoacetophenone (BAP) and U10029A, inhibited spontaneous PRL release. BAP also decreased basal release of [3H]arachidonic acid, blocked melitin-induced PRL secretion, and inhibited melittin-induced [3H] arachidonic acid release. Exogenous arachidonic acid at doses from 10 nM to 1 microM stimulated PRL secretion. The phospholipase A2 inhibitor BAP blocked TRH- and vasoactive intestinal peptide-induced PRL release, whereas U10029A blocked cAMP-induced and blunted TRH- and vasoactive intestinal peptide-induced PRL release. The hydrolysis of membrane phospholipids generating free arachidonic acid and lysophospholipid under our experimental conditions correlated with PRL secretion in GH3 cells. Addition of arachidonic acid to the culture medium stimulated PRL secretion. These data suggest that release of arachidonic acid and its subsequent actions may participate in the intracellular regulation of PRL secretion.

The composition of lipids and fatty acids determined at various stages of haploid and diploid generations in the fern Adiantum capillus‐veneris

The composition of lipids and fatty acids was determined at various developmental stages of gametophytes and sporophytes in the fern Adiantum capillus‐veneris L. When the lipid content was expressed per g fresh weight, triacylglycerol was a major reserve lipid in spores and remained the dominant lipid in the gametophytes up to the 15th day after germination, but it was a minor one in the pinnae of sporophytes. In contrast, triterpenoids were abundant in sporophytes but not detected in gametophytes. When the content of fatty acids was expressed in percentage of the total fatty acids, the content of arachidonic acid in phosphatidylcholine and linolenic acid in diacyglyceryltrimethylhomoserine and phosphatidylcholine was significantly higher in both pinnae and petioles of sporophtes than in gametophytes. Significant differences in fatty acid composition of phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol and triacylglycerol were also noted between gametophytes and pinnae of sporophytes. All these differences were attributed to the difference of generation rather than tissue differences or age.The content of monogalactosyldiacylglycerol, hexadecatrienoic acid in monogalactosyldiacylglycerol, and 3‐trans hexadecenoic acid in phosphatidylglycerol was higher in the pinnae of sporophytes than in gametophytes or in young leaves of sporophytes. Electron microscopy of the ultrastructure of chloroplasts indicated that the high content of these components was consistent with the development of chloroplasts in pinnae.

Role of Ca2+ in phosphatidylinositol response and arachidonic acid release in formylated tripeptide- or Ca2+ ionophore A23187-stimulated guinea pig neutrophils.

The role of Ca2+ in phospholipid metabolism and arachidonic acid release was studied in guinea pig neutrophils. The chemotactic peptide formylmethionyl-leucyl-phenyl-alanine (fMLP) activated [32P]Pi incorporation into phosphatidylinositol (PI) and phosphatidic acid (PA) without any effects on the labeling of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS). This activation was observed in Ca2+-free medium. Even in the neutrophils severely deprived of Ca2+ with EGTA and Ca2+ ionophore A23187, the stimulated labeling was not inhibited. When [3H]arachidonic acid-labeled neutrophils were stimulated by fMLP, a loss of [3H]arachidonic acid moiety in PI and the resultant increase in [3H]arachidonyl-diacylglycerol (DG), -PA, and free [3H]arachidonic acid was marked within 3 min. With further incubation, a loss of [3H]arachidonic acid in PC and PE became significant. These results suggest the activation of phospholipase C preceded the activation of phospholipase A2. In Ca2+-free medium, the decrease in [3H]arachidonyl-PI and the increase in [3H]arachidonyl-PA were only partially inhibited, although the release of [3H]arachidonic acid and a loss of [3H]arachidonyl-PC and -PE was completely blocked. These results show that PI-specific phospholipase C was not as sensitive to Ca2+ deprivation as arachidonic acid cleaving enzymes, phospholipase A2, and diacylglycerol lipase. Ca2+ ionophore A23187, which is known as an inducer of secretion, also stimulated [32P]Pi incorporation into PI and PA, although the incorporation into other phospholipids, such as PC and PE, was inhibited. This stimulated incorporation seemed to be caused by the activation of de novo synthesis of these lipids, because the incorporation of [3H]glycerol into PA and PI was also markedly stimulated by Ca2+ ionophore. But the chemotactic peptide did not increase the incorporation of [3H]glycerol into any glycerolipids including PI and PA. Thus, it is clear that fMLP mainly activates the pathway, PI leads to DG leads to PA, whereas Ca2+ ionophore activates the de novo synthesis of acidic phospholipids. When [3H]arachidonic acid-labeled neutrophils were treated with Ca2+ ionophore, the enhanced release of arachidonic acid and the accumulation of [3H]arachidonyl-DG, -PA with a concomitant decrease in [3H]arachidonyl-PC, -PE, and -PI were observed. Furthermore, the Ca2+ ionophore stimulated the formation of lysophospholipids, such as LPC, LPE, LPI, and LPA nonspecifically. These data suggest that Ca2+ ionophore releases arachidonic acid, unlike fMLP, directly from PC, PE, and PI, mainly by phospholipase A2. When neutrophils were stimulated by fMLP, the formation of LPC and LPE was observed by incubation for more than 3 min. Because a loss of arachidonic acid from PI occurred rapidly in response to fMLP, it seems likely the activation of PI-specific phospholipase C occurred first and was followed by the activation of phospholipase A2 when neutrophils are activated by fMLP...