Influence Of Arachidonic Acid Research Articles

Effect of 20-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic and Arachidonic Acids on Differentiation of Neurospora crassa

Comparative analysis of the influence of arachidonic acid and its derivatives, 3-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic and 20-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic acids, on the formation of sexual and asexual reproductive structures in Neurospora crassa demonstrated that the presence and location of the hydroxyl group in unsaturated fatty acid determine the biological effect of the compound. In the presence of 5 μM of arachidonic acid, 20-HETE, and 3-HETE, vegetative spore formation in the light decreased by 45, 31, and 40%, respectively, indicating a similarity in the mechanisms of their action on the light-dependent asexual reproduction of the fungus. However, the effects of these compounds on the sexual process of N. crassa were radically different. Gas chromatography–mass spectrometry (GC–MS) revealed a fourfold increase in the monounsaturated oleic acid content in N. crassa cells after the addition of arachidonic acid. In the same time, the effect was not observed after the addition of 20-HETE. On the other hand, the increase in the linoleic acid content in the fungal mycelia was higher with 20-HETE.

Effects of arachidonic acid on L-type calcium channel and its mechanism of antiarrhythmia

Objective To study the influence of arachidonic acid (AA) on L-type calcium channel in rabbits sin-gle cardiomyocyte and its mechanism of antiarrhythmia. Method The single ventricular cardiomyocyte was isolat-ed by using enzyme dispersion method and whole-cell clamp-patch technique was used to record L-type calcium current.All data were analyzed using ANOVA. Results AA inhibited Ica-L in a concentration-dependent manner. The application of 3 μmol/L, 10 μmol/L and 20 μmol/L arachidonic acid reduced the density of peak Ica-L from (10.79±0.93)pA/pF to (8.99±0.43)pA/pF to (7.60±0.35)pA/pF and to (5.60±0.30)pA/pF, respctive-ly (n=7, P<0. O1 ). The Ica-Lpartially resumed after washout. The AA up-shifted the I-V curves of Ica-L without changes of their shape,peak and reverse potentials. The AA also markedly shifted the inactivation curve to left, and prolonged the recorvery time from inactivation,but did not change the curve of calcium channel activation. Con-clustions By acceleration of L-type calcium channel inactivation and prolongation of recorvery time from inactiva-fion,arachidonic acid can reduce the calcium ion influe and prolong effective refractory period, playing the role of antiarrhythmia. Key words: Arachidonic acid; Ventricular myocytes; Arrhythmia; L-type calcium channel; Patch clamp

Influence of arachidonic acid and phytoviruses on the hormonal system of potato plants grown in vitro

Changes in the phytohormonal system during the development of antivirus resistance was investigated. This resistance was induced by arachidonic acid (AA) in potato plants (Solanum tuberosum L.) grown in vitro. The plants in tubes were treated with AA 7 days before infection with tobacco mosaic virus or potato X virus. These plants were used for ABA, IAA, and cytokinin quantification. As a rule, phytoviruses increased ABA and cytokinin levels and decreased that of IAA in both immunized and unimmunized plants. AA significantly decreased the phytovirus content in potato plants at least during 3 weeks. In general, AA immunization acted as a limiting factor for increasing the ABA and cytokinin concentrations during virus pathogenesis in experimental plants. However, no regularity in the changes of the IAA concentration was noted. The data obtained showed that AA-induced changes in the hormonal system could be an important factor in the mechanism of plant resistance against phytopatogenic viruses.

Docosahexaenoic and Arachidonic Acid Influence on Preterm Baboon Retinal Composition and Function

Dietary n-3 polyunsaturated fatty acid deficiency and prematurity are both associated with suboptimal visual function in nonhuman primates and in humans. This study reports measurements of retinal long chain polyunsaturate (LCP) concentrations and electroretinogram (ERG) parameters for term and preterm neonatal baboons consuming clinically relevant diets. ERGs and retinal fatty acid compositions were obtained from baboon neonates in four groups: term-delivered/breast-fed (B), term/formula-fed (T-), preterm/formula-fed (P-), and preterm/formula (P+) supplemented with long chain polyunsaturates. Initial a-wave slope change (ä), a-wave amplitude (a(amp)) and implicit time (a(i)), and b-wave amplitude (b(amp)) and implicit time (b(i)) were determined and correlations to retinal fatty acid concentrations were evaluated. The P+ group ä and b(amp) significantly improved between 0 and 4 weeks' adjusted age, whereas no P- group parameter improved with age. At four weeks, both a(amp) and b(amp) were significantly greater in group B than in all other groups, and ä and a(i) were greater for P+ than for P-. Concentrations of 22:6n-3, 22:5n-3, and Sigman-3 and the 22:5n-6/22:6n-3 ratio correlated positively with improved retinal response parameters, whereas 22:5n-6, 22:4n-6, 20:4n-6, 20:3n-6, 20:2n-9, 20:1n-9, and 18:1n-9 all correlated negatively (P < 0.05); saturates were uncorrelated. The parameters most linearly related to retinal 22:6n-3 were ä, a(i), and a(amp). Retinal 20:4n-6 concentrations were not influenced by prematurity or supplementation. Breast-feeding optimizes retinal response in 4-week-old baboons. Formula supplemented with 22:6n-3 prevents a decrease in retinal 22:6n-3 and improves preterm ERG parameters compared with unsupplemented formula. Retinal 22:6n-3 status is most closely associated with a-wave parameters.

Arachidonic acid potentiates the feedback response of mesangial BKCa channels to angiotensin II.

The influence of arachidonic acid (AA) on the feedback regulation of mesangial contraction by large Ca(2+)-activated K+ channels (BKCa) was determined through single-channel analysis using the patch clamp method. The mesangial BKCa is a low-gain negative feedback inhibitor of contraction that is activated in response to agonist-induced Ca2+ transients and membrane depolarization. AA activated BKCa in cell-attached patches in a dose-dependent manner with a maximal effect at 400 nM and a half-maximal response at 49 nM. In inside-out patches, AA directly activated BKCa with a maximal effect at 400 nM. BKCa was activated significantly in response to addition of 100 nM ANG II in the presence but not the absence of AA. Since it was shown previously that fatty acids stimulated both soluble and membrane-bound guanylyl cyclase, we determined whether AA activated BKCa by interfering with cGMP-mediated signal transduction pathways. It was previously shown that 10 microM cGMP, via cGMP-dependent protein kinase, activated BKCa in a biphasic manner with an early increase in probability of a channel existing in an open state (Po) and a subsequent inactivation mediated by protein phosphatase 2A (PP2A). We found that 10 microM dibutyryl-cGMP enhanced BKCa activity in an additive manner with saturating concentrations (400 nM) of AA. Moreover, the inactivation phase mediated by PP2A was not abolished. Thus AA does not affect the phosphorylation/dephosphorylation regulatory cycle for BKCa. It is concluded that AA potentiates the ANG II feedback response of BKCa by a mechanism that is independent of the phosphorylation cycle.

Fish oil fatty acids and human platelets: Dose-dependent decrease in dienoic and increase in trienoic thromboxane generation

Dietary enrichment of membrane phospholipids with n-3 (fish-oil-derived) fatty acids has attracted attention as a putative therapeutic regimen for suppression of inflammatory and coagulatory events. Use of n-3 fatty-acid-enriched lipid infusions for parenteral nutrition results in micromolar concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DCHA) in the plasma-free fatty acid fraction. We investigated the influence of free EPA and DCHA on platelet thromboxane (Tx) A 2 and A 3 formation by using a recently developed high performance liquid chromatography-ELISA technique for separate quantification of the stable hydrolysis products TxB 2 and TxB 3. Washed human thrombocytes were incubated with free arachidonic acid (AA; 1 μM), A23187 (0.1 μM) or thrombin (5 U/mL) for stimulation; all regimens provoked large quantities of TxA 2 in the absence of TxA 3. Simultaneous admixture of free EPA or free DCHA to the incubation medium (concentration range, 0.01–50 μM) largely suppressed platelet TxA 2 generation in response to all stimuli used in a dose-dependent manner. The effective concentration with 50% influence of arachidonic acid was 4.2 μM, whereas the inhibitory concentration with 50% effect of EPA and DCHA were both in the same order of magnitude but differed with the nature of the agonist (0.2–7 μM). Platelet (co-)incubation with EPA, but not DCHA, provoked dose-dependent synthesis of n-3-lipid-derived thromboxane: kinetics of formation and absolute quantities of TxA 3 approximated 20% of the respective TxA 2 data upon stimulation with AA. Both EPA and DCHA dose-dependently suppressed U46619-provoked platelet aggregation. We conclude that EPA and DCHA are potent competitive inhibitors of TxA 2 generation by intact platelets, with EPA acting as poor substrate and DCHA being no substrate for the cyclooxygenase/thromboxane synthase complex. Enrichment of the plasma-free fatty acid fraction with n-3 lipids may offer a therapeutic regimen to suppress the synthesis of the potent proaggregatory and vasoconstrictory agent TxA 2.

Influence of arachidonic acid on indices of phospholipase A2 activity in the human neutrophil.

The present studies were conducted to understand better the regulation of phospholipase A2 (PLA2)-dependent mobilization of lipid mediators by arachidonic acid (C20:4). After stimulation of human neutrophils, g.l.c./m.s. analysis of non-esterified fatty acids indicated that the quantity of C20:4 increased as a function of time after stimulation, from undetectable quantities to > 800 pmol/10(7) cells. In contrast with C20:4, the quantities of other free fatty acids such as oleic and linoleic were high in resting cells and did not change after stimulation. Some 15% of the C20:4 released from cellular lipids remained cell-associated. To examine the effect of C20:4 on its own release, neutrophils were exposed to [2H8]C20:4, to differentiate it by g.l.c./m.s. from naturally occurring C20:4. In A23187-stimulated neutrophils, low concentrations (5-10 microM) of [2H8]C20:4 added just before A23187 increased the quantity of C20:4 produced by the cell, whereas higher concentrations (30-50 microM) decreased the quantity of C20:4 released from phospholipids. As other measures of PLA2 activity, the effects of C20:4 on production of platelet-activity factor (PAF) and leukotriene B4 (LTB4) were assessed. C20:4 treatment just before stimulation of neutrophils blocked PAF and LTB4 production in a concentration-dependent manner (IC50 10-20 microM). The effect of C20:4 was not blocked by the cyclo-oxygenase inhibitor naproxine (10 microM), nor could it be mimicked by 1 microM LTB4, 5-hydroxyeicosa-6,8,11,14-tetraenoic acid (5HETE), 5-hydroperoxyeicosa-6,8,11,14-tetraenoic acid (5HPETE) or 15-hydroxyeicosa-5,8,11,13-tetraenoic acid (15HETE). The 5-lipoxygenase (5LO) inhibitor zileuton induced a concentration-dependent decrease in PAF, with a maximal effect of a 50% decrease at 10-50 microM. The decrease in PAF by the 5LO inhibitor could not be circumvented by addition of 1 microM 5HETE, 5HPETE and LTB4, and may be attributed to the capacity of zileuton to increase the quantity of C20:4 in A23187-treated neutrophils. The inhibitory effect of C20:4 (20-40 microM) on PAF production could be antagonized by the protein kinase C inhibitor staurosporine (30 nM), but not by inhibitors of protein kinase A, tyrosine kinase or calmodulin kinase II. Taken together, these data demonstrate that C20:4 is selectively released from membrane phospholipids of A23187-stimulated neutrophils, and this C20:4 may play an important role in regulating the mobilization of C20:4 by altering PLA2 activity.

Intestinal zinc transport: Influence of streptozotocin-induced diabetes, insulin and arachidonic acid

The influence of arachidonic acid (AA) on the zinc flux rates of jejunal segments, isolated from streptozotocin-induced diabetic rats injected with saline or with insulin, was investigated using an Ussing chamber technique. Although the zinc flux rates from mucosa-to-serosa (J ms) of normal rats were inhibited by addition of 5 μM AA to the jejunal segment bathing medium (46.4±5.0 vs 32.6±4.3 nmol/hr/cm 2), AA had no effect on the J ms of diabetic rats either with or without insulin treatment. Induction of diabetes also significantly reduced J ms (46.4±5.0 vs 22.1±4.9 nmol/hr/cm 2), but 3 day insulin treatment (NPH 8 U/Kg/day subcutaneously) did not reverse this effect (29.2±5.1 nmol/hr/cm 2). Addition of AA to the serosal side did not significantly alter the zinc flux rate from serosa-to-mucosa (J sm) in either control, diabetic or diabetic rats treated with insulin. The net zinc absorption rate (J net) of jejunal segments was decreased in diabetic rats compared to controls (13.2±3.0 vs −0.7±2.1 nmol/hr/cm 2), but normalization of blood glucose with 3 day insulin treatment did not increase J net. Addition of AA was associated with a tendency to increase zinc uptake capacity. This change reached statistical significance in insulin treated diabetic rats. Short-circuit current (I sc) for diabetic rats was increased compared to controls but addition of AA to the mucosal side bathing medium decreased I sc in all groups. The results indicate that the zinc flux rate in the small intestine of streptozotocin-induced diabetic rats is decreased, that zinc uptake capacity of the small intestine does not directly reflect the zinc flux rate across the small intestine, and that AA or one of its metabolites may play a significant role in the control of the zinc flux across the intestinal epithelium.

Comparison of histamine release and prostaglandin E2 production of human basophils in atopic and normal individuals

The influence of arachidonic acid (AA) metabolism upon histamine release (HR) from human basophils after stimulation with anti-IgE was studied in 23 atopic and 11 normal individuals. HR occurred significantly faster in atopics than in normals; the total amount of HR after a 40 min incubation period was not significantly different between the two groups. Indomethacin and acetylsalicylic acid (ASA) increased the quantity of HR significantly both in atopics and normals without influencing the time course. Addition of exogenous PGE2 decreased HR; here atopics were more affected than normals 5 and 10 min after challenge with anti-IgE. Production of PGE2 after stimulation with anti-IgE was very low in both groups (in the range of 30-50 pg/10(6) cells) and often below detection limit (10-20 pg/ml). Addition of glutathione (GSH), a coenzyme of PGE2-isomerase, increased PGE2 production 2 to 5-fold during stimulation with anti-IgE. These data support the idea that arachidonic acid metabolites play an important role in modulating the "releasability" of human basophils. It is suggested that the basophils of atopic individuals may release their histamine faster than normals - perhaps on the basis of a more slowly acting endogenous feedback mechanism by PGE2. Both phenomena support the idea of an altered "releasability" of basophils from atopics compared to normals.

Influence of arachidonic acid on vasoconstrictor responses in the rabbit hindquarters vascular bed

The effects of infusion of arachidonic acid (AA) on responses to pressor hormones and sympathetic nerve stimulation were investigated in the hindquarters vascular bed of the rabbit. During infusion of AA, vasoconstrictor responses to norepinephrine, nerve stimulation and angiotensin II were reduced to a similar extent. In addition, AA decreased hindquarters perfusion pressure and systemic arterial pressure. Following the administration of indomethacin, vasoconstrictor responses as well as perfusion pressure and aortic pressure remained unchanged during infusion of AA. The present data show that AA possesses the ability to modulate responses to nerve stimulation and pressor hormones. In addition, AA dilates the hindquarters vascular bed and produces a systemic depressor response. The present data suggest that cyclooxygenase products possessing vasodilator activity may mediate the effects of AA on the sympathetic nervous system and responses to pressor hormones in the rabbit hindquarters vascular bed.

Role of arachidonic acid in platelet aggregation induced bySalmonella typhimurium endotoxin

The platelet aggregation reaction was used to assess the influence of arachidonic acid (AA), endotoxin (E) S. typhimurium and ADP on platelet aggregation properties. All the three substances induced platelet aggregation. A higher degree of aggregation was attained by the application of E combined with AA and ADP as compared with the effects produced by E and ADP alone. Prolonged incubation of platelet-rich plasma (PRP) samples with E led to an essential decrease of the aggregation degree on ADP addition. Incubation of PRP samples with E and ADP did not evoke any analogous decrease in the platelet aggregation degree. The data obtained indicate that AA stimulates platelet aggregation induced by E and ADP.

Effect of corticosterone, hydrocortisone and prostaglandin fatty acid precursors on the spontaneous motility of the uterus isolated from ovariectomized rats

The effect of corticosterone (CC, 0.4 and 1 μg/ml) and of hydrocortisone (HC, 20 and 40 μg/ml) on the spontaneous motility and on prostaglandin (PG) generation in the uterus from ovariectomized rats, was studied. Both concentrations of CC depressed significantly the frequency of contractions but the isometric developed tension was affected only by the higher dose. HC concentrations whereas the contractile frequency was only depressed by the higher one. The CC-inhibited motility was accompanied by a reduction in the amount of PGs released from the uterus into the bath solution. In addition, the influence of arachidonic acid (AA), linoleic acid (LA) and gamma-linolenic acid (γ-LA) - 1 or 2 μg/ml - on the depression evoked by CC, were also explored. The fatty acids had no effect on the spontaneous uterine motility except in the case of γ-LA at 1 μg/ml. γ-LA completely blocked the CC-evoked reduction of bothe tension and frequency; AA (1μg/ml) elicited a reversion only on frequency whereas LA had no effect at all. This reversion by a fatty acid PG-precursor might indicate that CC is able to diminish substrate availability for PG synthesis in the rat uterus.

Influence of Arachidonic Acid and Indomethacin on Uterine and Vaginal Motility in the Domestic Hen

The influence of arachidonic acid and indomethacin on in vitro uterine and vaginal motility has been studied on the domestic hen. Arachidonic acid induced a prostaglandin-like contraction of isolated uterine strips and a PGE2-like relaxation of vaginal strips. These effects were inhibited by indomethacin. Incubation of tissue strips with indomethacin resulted in a suppression of spontaneous motility in uterine strips and in an activation of vaginal spontaneous activity.