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R C Murphy

Publications and source records attributed to R C Murphy.

At least 73 records · Page 4Linked to original sources
PubMed1995

Metabolism of leukotriene B4 in cultured hepatoma cells.

Incubation of leukotriene B4 (LTB4) with Hep G2 cells (a human-derived hepatoma cell line) resulted in the production of several metabolites indicative of alternative pathways of LTB4 metabolism not previously observed in normal hepatocytes. The major extracellular LTB4-derived metabolites were structurally identified using mass spectrometry and ancillary techniques including electrospray ionization. The major metabolite was 10-hydroxy-4,6,8,12-octadecatetraenoic acid (10-HOTE), an unexpected metabolite which lost the hydroxy group at carbon 5 from the parent LTB4. Two other major metabolites were 3(R)-hydroxy-LTB4 and 3(S)-hydroxy-LTB4. The formation of these three metabolites revealed that beta-oxidation from the carboxyl terminus can be a significant metabolic pathway for degradation of this hydroxy unsaturated fatty acid. The normal hepatocyte LTB4-derived metabolite, 20-carboxy-LTB4, was observed as only a minor product. The metabolic profile for Hep G2 cells suggests that the efficient cytochrome P-450 pathway involved in omega-oxidation in typical hepatocytes is absent in these cells. Several minor metabolites were also identified which included dihydro products resulting from metabolism by a 12-hydroxydehydrogenase/delta 10-reductase pathway. The formation of the major metabolite reveals the operation of steps in beta-oxidation of hydroxy, unsaturated fatty acids not anticipated by previously identified steps of fatty acid beta-oxidation.

Biotransformation↗
PubMed1995

Isoleukotrienes are biologically active free radical products of lipid peroxidation.

The free radical oxidation of arachidonic acid esterified to glycerophospholipids is known to generate complex metabolites, termed isoprostanes, that share structural features of prostaglandins derived from prostaglandin H2 synthase. Furthermore, certain isoprostanes have been found to exert biological activity through endogenous receptors on cell surfaces. Using mass spectrometry and ancillary techniques, the free radical oxidation of 1-hexadecanoyl-2-arachidonoyl-glycerophosphocholine was studied in the search for products of arachidonic acid isomeric to the leukotrienes that are derived from 5-lipoxygenase-catalyzed metabolism of arachidonic acid. Several conjugated triene metabolites were chromatographically separated from known 5-lipoxygenase products and structures characterized as 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid esterified to the glycerophosphocholine backbone. We have termed these products as B4-isoleukotrienes. Following saponification some, but not all, B4-isoleukotrienes were found to exert biological activity in elevating intracellular calcium in Indo-1-loaded human polymorphonuclear leukocytes. This activity could be blocked by a leukotriene B4 receptor antagonist. An EC50 of approximately 30 nM was determined for one unique B4-isoleukotriene with a relative retention index of 2.54. We have shown that free radical processes can lead to the formation of biologically active isoleukotrienes in glycerophosphocholine liposomes, and we propose that B4-isoleukotrienes may also be formed in membrane glycerophospholipids as a result of lipid peroxidation during tissue injury. Such B4-isoleukotrienes could then mediate events of tissue damage through activation of leukotriene B4 receptors on target cells.

Arachidonic Acid↗
PubMed1995

Identification of functional platelet-activating factor receptors on human keratinocytes.

Platelet-activating factor (PAF) is a potent inflammatory mediator that has been shown to be produced by human keratinocytes and is thought to play a role in cutaneous inflammation. Immunofluorescence and radioligand binding studies were used to characterize PAF receptors (PAF-R) on human keratinocytes and the human epidermoid cell lines A-431 and HaCaT. Indirect immunofluorescence studies demonstrated anti-PAF-R staining of primary cultures of human keratinocytes, A-431 cells, and HaCaT cells. Primary cultures of human fibroblasts and the melanoma cell line SK-30 failed to show immunostaining above that seen with control antiserum. With indirect immunofluorescence studies of sections of normal human skin, a granular anti-PAF-R staining pattern was noted on the keratinocyte cell membranes. A-431 cells readily metabolized PAF by deacetylation-reacylation at 37 degrees C, but not at 4 degrees C. Binding studies on crude membrane preparations of A-431 cells conducted at 4 degrees C demonstrated specific binding that reached saturation by 120 min. Scatchard analysis of PAF binding data revealed a single class of high-affinity (KD = 6.3 +/- 0.3 nM) PAF binding sites. The immunofluorescence and radioligand binding sites were shown to be functional PAF-Rs, as 10 pM to 1 microM PAF increased intracellular calcium in primary cultures of human keratinocytes, A-431 cells, and HaCaT cells, whereas PAF treatment of primary cultures of human fibroblasts or the melanoma cell line SK-30 did not result in changes in the intracellular calcium concentration. The structurally dissimilar PAF-R antagonists CV-6209, Ro19-3704, and alprazolam all inhibited the PAF-induced calcium changes in A-431 cells. The CV-6209 inhibition was seen at doses that competed with the PAF binding to these cells. These studies provide the first evidence for the presence of a functional PAF-R expressed on human keratinocytes, suggesting that this lipid mediator may play an important role in normal keratinocytes or in inflammatory dermatology.

Calcium↗
PubMed1994

Eosinophil 15-lipoxygenase is a leukotriene A4 synthase.

5-Lipoxygenase is the first committed enzyme in the leukotriene biosynthetic pathway and is known to catalyze not only the first oxygenation of arachidonate to form 5(S)-hydroperoxyeicosatetraenoic acid (5(S)-HPETE), but also dehydration of this intermediate into leukotriene A4 (LTA4) by an activity termed leukotriene A4 synthase. Inhibition of cytosolic 5-lipoxygenase prepared from human blood granulocytes with zileuton (100 microM) was virtually complete, but LTA4 synthase activity was only inhibited by 47%. Structural characterization of eicosanoids synthesized in these preparations revealed an abundance of 15-lipoxygenase metabolites including 15-HETE when arachidonate was used as substrate and 5(S),15(S)-dihydroxy-6,8,11,13(E,E,Z,Z)-eicosatetraenoic acid when 5(S)-HPETE was used as substrate. When neutrophils were prepared that contained less than 1% eosinophil contamination, zileuton was found to almost completely inhibit all 5-lipoxygenase, as well as LTA4 synthase products. Immunochemical analysis of the supernatants from purified neutrophils and eosinophils confirmed the previous observation that neutrophils do not express 15-lipoxygenase. Incubation of 5(S)-HPETE with recombinant mammalian 15-lipoxygenase resulted in the formation of 6-trans-LTB4 and 6-trans-12-epi-LTB4 as LTA4 products, as well as the 12-lipoxygenase product 5(S),12(S)-diHPETE. The mechanism of action of 15-lipoxygenase acting as an LTA4 synthase is proposed to involve removing the pro-R hydrogen atom at carbon-10 of 5(S)-HPETE, which is antarafacial to the hydroperoxy group to yield LTA4.

Arachidonate 15-Lipoxygenase↗
PubMed1994

Characterization of chain-shortened oxidized glycerophosphocholine lipids using fast atom bombardment and tandem mass spectrometry.

Oxidized glycerophosphocholine (GPC) lipids produced by free-radical-initiated lipid peroxidation have been reported to activate human polymorphonuclear leukocytes exerting an effect through the platelet-activating factor receptor, yet few methods have been developed to characterize intact oxidized phospholipids, which may be present in small quantities. In this paper we detail the fast atom bombardment and collision-induced dissociation behavior of 1-hexadecanoyl-2-(5-oxopentanoyl)-GPC and 1-hexadecanoyl-2-pentanedioyl-GPC, two prototypic oxidized glycerophosphocholine lipids produced by hydroxyl radical-initiated peroxidation of 1-hexadecanoyl-2-arachidonoyl-GPC. Identities of these two products were established first using EI-GC/MS to analyze the corresponding diglyceride tert-butyldimethylsilyl ether derivatives. The aldehyde moiety of 1-hexadecanoyl-2-(5-oxopentanoyl)-GPC was found to react with FAB amine-containing liquid matrices (e.g., diethanolamine) to form an oxazolidine derivative (87 u increase in mass). No reaction was observed with matrices such as glycerol, thioglycerol, and 3-nitrobenzylalcohol. This derivatization can be used to distinguish an aldehyde-containing oxidized phospholipid from isobaric species not containing an aldehyde moiety. Results also showed that 1-hexadecanoyl-2-pentanedioyl-GPC formed primarily [M-H]- ions rather than the [M-15], [M-60], and [M-86] negative ions expected for GPC lipid species. The ionized omega-carboxyl group of the sn-2 substituent allowed the phosphocholine moiety to remain as a zwitterion. Following collision-induced dissociation, a N-methyl group from the choline was transferred to the omega-carboxyl of the sn-2 substituent prior to generation of the carboxylate anions, which resulted in a 14-u increase in the observed sn-2 carboxylate anion.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycerylphosphorylcholine↗
PubMed1994

Incorporation of stable isotope-labeled arachidonic acid into cellular phospholipid molecular species and analysis by fast atom bombardment tandem mass spectrometry.

The source of arachidonic acid metabolized to eicosanoids by 5-lipoxygenase was studied in a cultured neoplastic mast cell using a stable isotope tracer and tandem mass spectrometry strategy. Selected reaction monitoring and fast atom bombardment were used to analyze eight major arachidonate molecular species of glycerophosphocholine, nine major molecular species of glycerophosphoethanolamine, three major species of glycerophosphocholine, nine major molecular species of glycerophosphoethanolamine, three major species of glycerophosphoinositol, and three major glycerophosphoserine molecular species. Incubation of the mast cells with (2H8)arachidonic acid led to a time-dependent isotopic incorporation in each of these molecular species. Following stimulation with calcium ionophore A23187, the isotope incorporation of leukotriene B4 (LTB4) was found to be higher than that of the major arachidonate-containing glycerophospholipid molecular species. The isotope incorporation of LTB4 was similar to that found for free arachidonic acid present in the unstimulated cell. In order to prevent direct labeling of the intracellular, free arachidonic acid pool, (2H4)linoleic acid was added to the culture medium as a biochemical precursor of labeled arachidonic acid. There was a time-dependent increase of the specific incorporation of labeled arachidonic acid into each of the phospholipid molecular species of each lipid class after incubation with (2H4)linoleic acid. Importantly, (2H4)linoleic acid incubation also resulted in deuterium-labeled arachidonic acid in the free arachidonic acid, intracellular pool. The arachidonic acid isotopic incorporation in this pool very closely correlated with the isotopic incorporation of LTB4 (correlation coefficient 0.97) synthesized after A23187 stimulation, while the isotopic incorporation of the extracellularly released, not esterified arachidonic acid, after stimulation, did not.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Stereochemical analysis and biological activity of 3-hydroxy-leukotriene B4: a metabolite from ethanol-treated rat hepatocytes.

Leukotriene B4 (LTB4), a biologically active metabolite derived from arachidonic acid by the 5-lipoxygenase cascade, is inactivated by cytochrome P-450-dependent omega-hydroxylation followed by second oxidation into a omega-carboxyl group. In many tissues, this second step is mediated by alcohol dehydrogenase. Isolated rat hepatocytes metabolized LTB4 in the presence of ethanol and ethoxyresorufin into substantial quantities of 3-hydroxy-LTB4 as determined by mass spectrometry. The absolute configuration of this metabolite was found to be greater than 98% 3(S)-hydroxy-LTB4 by comparison to synthetic standards. Investigation of the pharmacologic properties of the 3(S)- and 3(R)-hydroxy-LTB4 revealed that both caused a significant increase in intracellular free calcium in human neutrophils at 1 microM. Both enantiomers also induced thromboxane A2 release from the isolated guinea pig lung in a dose-dependent manner. This activity was fully blocked by a specific LTB4 receptor antagonist, LY223982, with an IC50 of 0.21 microM for LTB4. These results suggested that activation of the LTB4 receptor does not involve significant recognition of the carbon atoms close to the carboxyl moiety of LTB4. The failure of the hepatocyte to metabolically inactivate LTB4 in the presence of ethanol may be of importance to humans, particularly because the bioactive metabolite 3(S)-hydroxy-LTB4 was further metabolized by human neutrophils significantly more slowly than LTB4.

Animals↗
PubMed1993

Metabolism of leukotriene B4 by cultured human keratinocytes. Formation of glutathione conjugates and dihydro metabolites.

Six previously unidentified leukotriene (LT) B4 metabolites formed during incubation of LTB4 with human keratinocytes in primary culture indicate the importance of the 12-hydroxyeicosanoid dehydrogenase pathway in LTB4 metabolism. The ultraviolet absorption spectra obtained for all keratinocyte metabolites revealed the presence of a conjugated diene structural moiety rather than the conjugated triene structure of LTB4. Metabolites were characterized using fast atom bombardment-mass spectrometry, gas chromatography-mass spectrometry of the pentafluorobenzyl ester, trimethylsilyl ether derivatives and specific degradation reactions. The previously identified 10,11-dihydro-LTB4 and 10,11-dihydro-12-epi-LTB4 were observed as well as 20-OH-10,11-dihydro-LTB4, consistent with the reductase pathway of LTB4 metabolism. This pathway involves initial formation of 12-oxo-LTB4 catalyzed by 12-hydroxyeicosanoid dehydrogenase followed by reduction by delta 10-reductase. The most lipophilic metabolite of LTB4 was identified as 10-hydroxy-4,6,12-octadecatrienoic acid which could result from beta-oxidation reactions of LTB4 following reduction of the 10,11-double bond. One of the most abundant metabolites was characterized as 3,7,14-trihydroxy-8,10,16- docosatrienoic acid which could result from fatty acid elongation following reduction of the 10,11-double bond. Additional abundant LTB4 metabolites were identified that result from glutathione conjugation of 12-oxo-LTB4. These were characterized using fast atom bombardment-mass spectrometry and by chemical degradation using hypochlorous acid as well as transpeptidases. These metabolites were identified as 5,12-dihydroxy-6-glutathionyl-7,9,14-eicosatrienoic acid (c-LTB3), 5,12-dihydroxy-6-cysteinyl-glycyl-7,9,14-eicosatrienoic acid (d-LTB3) and 5,12-dihydroxy-6-cysteinyl-7,9,14-eicosatrienoic acid (e-LTB3). We propose that these metabolites result from a 1,8 Michael-type addition of glutathione to the 12-oxo-LTB4 intermediate.

Biotransformation↗
PubMed1993

Collision-induced dissociation of carboxylate anions from derivatized 5-lipoxygenase metabolites of arachidonic acid.

The low-energy collision-induced dissociations (CID) of carboxylate anions derived from pentafluorobenzyl ester, trimethylsilyl ether derivatives of four arachidonic acid metabolites of the 5-lipoxygenase pathway have been determined. These molecules include leukotriene B4 (LTB4), a potent chemotactic factor for the human neutrophil; 20-carboxy-LTB4, an inactive metabolite; 5-hydroxyeicosatetraenoic acid (5-HETE), a useful marker of 5-lipoxygenase activity within cells; and 5-hydroxyeicosanoic acid (5-HEA), which has been previously used for the quantitation of leukotriene E4. The carboxylate anion of 5-HEA (m/z 399) was found to decompose by the loss of trimethylsilanol as well as the loss of 146 u corresponding to the loss of trimethylsilanol followed by acrolein, a process specific for 5-hydroxy-containing saturated fatty acids. The loss of trimethylsilanol by a remote site mechanism is the major transition observed for the 5-HETE carboxylate anion (m/z 391). The ion formed (m/z 301) further decomposes by the loss of CO2 (m/z 257). The loss of trimethylsilanol is also seen at m/z 389 after collisional activation of the carboxylate anion of LTB4 (m/z 479) by a complex charge-driven mechanism, not the remote site fragmentation mechanism as expected. The loss of an olefinic proton possibly from carbon-7 is involved as well as an oxygen atom derived from the carboxylic acid moiety. The loss of two trimethylsilanol neutral molecules gives rise to ions seen at m/z 299. Isotopic labeling studies revealed that two isobaric ions are present at m/z 299. Both of these ions involve the loss of trimethylsilanol from the carbon-12 position according to remote site mechanisms, but only one has lost the olefinic proton at carbon-7 and, therefore, likely originates from the further decomposition of the ion (m/z 389) described above. An additional ion seen at m/z 317 is attributed to the loss of trimethylsilyl ether (TMS-O-TMS) following a charge-driven mechanism involving the oxygen atom at carbon-12. The 20-carboxy-LTB4 carboxylate anion (m/z 689) decomposes primarily through the loss of one and two trimethylsilanol moieties, but the base peak (m/z 491) is due to the loss of pentafluorobenzyl alcohol. This ion, likely a ketene, further gives rise to three ions by the sequential loss of one and two trimethylsilanols and TMS-O-TMS. All collision-induced decompositions of the carboxylate anions of these eicosanoids are characterized by losses of small neutral molecules from the derivatizing groups (TMS and pentafluorobenzyl) and little fragmentation of the carbon backbone.

Arachidonate 5-Lipoxygenase↗
PubMed1993

Low-energy fast atom bombardment tandem mass spectrometry of monohydroxy substituted unsaturated fatty acids.

The low-energy collision-induced dissociation (CID) of the carboxylate anions generated by fast atom bombardment ionization of monohydroxy unsaturated fatty acids derived from oleic, linoleic, linolenic and arachidonic acids were studied in a tandem quadrupole mass spectrometer. The collisional activation spectra revealed structurally informative ions as to the position of the hydroxyl substituent in relationship to the sites of unsaturation. Five mechanisms are proposed for the fragmentation of hydroxyl substituted unsaturated fatty acids and are dependent upon the presence of alpha- or beta-unsaturation sites. These mechanisms include charge-remote allylic fragmentation, charge-remote vinylic fragmentation, charge-driven allylic fragmentation, charge-driven vinylic fragmentation, and homolytic fragmentation by an oxy-Cope rearrangement process. The assignment of specific fragmentation pathways was supported in many instances with deuterium-labeled analogs. Although no single fragmentation mechanism appears to predominate, a rational approach to the interpretation of these CID spectra is proposed. The CID spectra of unknown compounds could be used to establish the hydroxyl substituent position in relationship to certain sites of unsaturation but would not be indicative of all double bond locations. The oxy-Cope rearrangement is specific for a structural unit, namely the 3-hydroxy-1,5-diene moiety.

Fatty Acids, Unsaturated↗
PubMed1993

Collision-induced dissociation of F2-isoprostane-containing phospholipids.

Free radical-induced lipid peroxidation results in the production of metabolites of arachidonic acid isomeric with prostaglandin F2 alpha. The formation of these compounds, termed F2-isoprostanes, occurs independent of the enzyme cyclooxygenase. The discovery that F2-isoprostanes can exert potent biological activity has suggested that they may mediate, to some extent, the biological responses to oxidant injury. Collision-induced dissociation of the [M-CH3]- ions from oxidized phospholipids isolated by extraction and normal phase high performance liquid chromatography from livers of rats treated with CCl4 to induce lipid peroxidation revealed several molecular species of phospholipids that had the F2-isoprostane esterified to the glycerophosphocholine backbone. Collision-induced dissociation of the [M-CH2CHN(CH3)3]- ion revealed that the F2-isoprostanes were primarily esterified at the sn-2 position of the glycerophospholipid as expected. Furthermore, tandem mass spectrometry of the carboxylate anion from the F2-isoprostane (m/z 353) resulted in the unique loss of 44 u characteristic of a 1,2-cyclic diol moiety such as that found in the PGF2-ring. These observations indicate that intact phospholipids containing fatty acyl groups of the isoprostane structure can be readily detected with tandem mass spectrometry even when present as minor components in a biological extract. Although no specific isomer identification can be made from the complex mixture, these techniques establish the existence of these novel metabolites of arachidonic acid esterified to glycerophospholipids.

Animals↗
PubMed1992

Fast atom bombardment tandem mass spectrometric identification of diacyl, alkylacyl, and alk-1-enylacyl molecular species of glycerophosphoethanolamine in human polymorphonuclear leukocytes.

Fast atom bombardment ionization with tandem mass spectrometry of both positive and negative ions is a useful technique for the identification of intact glycerophosphoethanolamine (GPE) phospholipids, providing information as to polar head group and fatty acyl substituents. In the identification of GPE molecular species, positive ion neutral loss scanning for 141 units was attempted to confirm the presence of the phosphoethanolamine polar head group. This scan was found to discriminate against the abundant subclass of phospholipids having an 1-O-alk-1'-enyl linkage, termed plasmalogens, as well as 1-O-alkyl ether species. The neutral loss process is suggested to involve attack of a carbonyl oxygen from either sn-1 or sn-2 on the sn-3 methylene carbon with loss of neutral phosphoethanolamine. Using FAB/MS/MS alone, it is not possible to differentiate between plasmalogens and other 1-O-alkyl ether molecular species having the same molecular weight. The combination of mild acid hydrolysis, which selectively hydrolyzes the labile 1-O-alk-1'-enyl bond, with subsequent FAB/MS/MS distinguished species of these distinct subclasses. Using these techniques and precursor ion scans for the arachidonoyl carboxylate anion, m/z 303, the arachidonic acid containing glycerophosphoethanolamine molecular species were identified and the relative abundance of arachidonoyl plasmalogen, alkylacyl, and 1,2-diacyl GPE molecular species in the human polymorphonuclear leukocyte (neutrophil) was determined to be 75.4%, 12.1%, and 12.5%, respectively. These values were not significantly different from that reported in the literature using conventional methodology.

Arachidonic Acid↗
PubMed1992

Reversible membrane association of neutrophil 5-lipoxygenase is accompanied by retention of activity and a change in substrate specificity.

Ionophore activation of the human polymorphonuclear neutrophil results in eicosanoid synthesis and the accumulation of inactive 5-lipoxygenase in a membrane compartment. We report here that inhibition of self-inactivation of 5-lipoxygenase in ionophore-treated neutrophils with the reversible inhibitor zileuton, results in the accumulation of active 5-lipoxygenase in the membrane fraction. In zileuton plus ionophore-treated cells, 77% of the specific activity of the cytosolic enzyme from resting cells was diverted to the membrane fraction compared to 22% of the activity translocated when ionophore alone was used to activate the neutrophils. Accumulation of active membrane-associated 5-lipoxygenase was inhibited and reversed by the 5-lipoxygenase translocation inhibitor MK-886. The membrane-associated 5-lipoxygenase was two times more efficient in the production of leukotriene A4 from arachidonate-derived 5-hydroperoxyeicosatetraenoic acid than the cytosolic enzyme. Unlike the cytosolic enzyme, membrane-associated 5-lipoxygenase could metabolize 12(S)- and 15(S)-hydroxyeicosatetraenoic acid to 5(S),12(S)- and 5(S),15(S)-dihydroxyeicosatetraenoic acid, respectively. The ability to metabolize hydroxy fatty acids was dependent upon 5-lipoxygenase-activating protein association, but was lost if 5-lipoxygenase was eluted from the membrane by MK-886. These studies reveal for the first time that significant quantities of active 5-lipoxygenase can be detected in the membrane fraction of activated neutrophils and show that membrane association can alter the substrate specificity of 5-lipoxygenase which is further evidence for the role of the membrane-associated enzyme in the synthesis of 5-lipoxygenase metabolites.

Arachidonate 5-Lipoxygenase↗
PubMed1992

Time-dependent utilization of platelet arachidonic acid by the neutrophil in formation of 5-lipoxygenase products in platelet-neutrophil co-incubations.

The biosynthesis of leukotrienes is known to occur through a series of complex processes which, in part, can be influenced by cell-cell interactions. Several studies have suggested that arachidonic acid availability is a major limiting step for leukotriene biosynthesis and that its transfer between cells can represent a significant source of this precursor. Accordingly, effect of time and source of arachidonic acid on transcellular leukotriene synthesis was studied in mixed platelet/neutrophil populations challenged with the calcium ionophore A23187. A time-dependent contribution of platelet-derived as well as neutrophil-derived arachidonate was found in the selective formation of neutrophil 5-lipoxygenase metabolites. Utilization of platelet or neutrophil arachidonate was followed by incorporation of radiolabeled arachidonic acid into platelet or neutrophil phospholipids prior to stimulation. Specific activity of liberated arachidonic acid along with numerous 5-lipoxygenase products (including LTB4, 20-hydroxy-LTB4, 5-HETE and LTC4) was determined in order to follow mass and radiolabel. A large amount of platelet-derived arachidonic acid was released in the first 1.5 min, whereas 10 min platelet-derived arachidonate was much lower in amount but significantly higher in specific activity, suggesting different precursor pools. The platelet-derived arachidonate was heavily utilized by the neutrophils at the early time points for formation of 5-HETE and delta 6-trans-LTB4 isomers, but appeared to contribute only marginally to the constitutive metabolism of neutrophil arachidonate into LTB4. Results from these experiments suggest different pools of 5-lipoxygenase in the neutrophil and indicate a time and source dependent modulation of arachidonate metabolism in mixed cell interactions.

Arachidonate 5-Lipoxygenase↗