Degranulation Of Polymorphonuclear Leukocytes Research Articles

Inhibition of degranulation of polymorphonuclear leukocytes by angiogenin and its tryptic fragment.

A degranulation inhibiting protein was purified to apparent homogeneity from plasma ultrafiltrates of patients with uremia using gel-permeation chromatography, ion-exchange chromatography, affinity chromatography on blue Sepharose, and ion-exchange chromatography on a Mono S HR 5/5 fast protein liquid chromatography column. The identity of the isolated degranulation inhibiting protein with angiogenin was demonstrated by amino acid sequence determination, immunoblotting, and identical inhibitory activity effects on leukocyte degranulation. At concentrations in the nanomolar range, the protein inhibited spontaneous degranulation of polymorphonuclear leukocytes (PMNL) to 40%. The protein discharge of cells, which were preincubated with nanomolar concentrations of angiogenin and then stimulated with the chemotactic peptide formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-leucine (FNLPNTL), was inhibited by 70%. Cellular functions such as chemotaxis, phagocytosis, and the oxidative respiratory burst were not obviously affected by angiogenin. A polyclonal antibody to human recombinant angiogenin abolished the inhibitory effect of the isolated protein upon PMNL. The same but reduced effect was induced by the disulfide C39-C92 containing tryptic angiogenin fragment L-H-G-G-S-P-W-P-P-C92-Q-Y-R-G-L-T-S-P-C39-K, indicating a new, so far unknown biologically active site of angiogenin which is different from the sites responsible for angiogenic or ribonucleolytic activity. Two synthetic peptides containing residues 83-95, one with S92 instead of C92, revealed the same inhibitory effect on the protein degranulation of PMNL as the entire tryptic fragment.

Detachment and cytolysis of human endothelial cells by proteinase 3.

Activation and degranulation of polymorphonuclear leukocytes (PMN) with release of proteolytic enzymes, such as proteinase 3 (PR3) and elastase, in the vessels of patients with Wegener's granulomatosis (WG) is thought to play an important role in the vascular endothelial cell damage. We have investigated the detachment and cytolysis of 51Cr-labeled umbilical vein endothelial cells (HUVEC) induced by highly purified, enzymatically active, PR3 and elastase. Incubation of confluent monolayers of HUVEC with 100 mU/ml of PR3 for 3 h at 37 degrees C generally resulted in 20% detachment and 30% cytolysis. Elastase (350 mU/ml) induced approximately 40% detachment and 15% cytolysis. Both PR3-mediated and elastase-mediated detachment and cytolysis were fully inhibited by alpha-1-proteinase inhibitor (alpha 1 PI), while anti-leukoprotease (ALP) only inhibited elastase-mediated endothelial damage. By selective inhibition of an azurophilic granule extract with either alpha 1PI or ALP we calculated that PR3 is responsible for 23% of the total detachment and cytolysis induced by the extract. Elastase was responsible for 60% of the detachment and 19% of the cytolysis. Detachment induced by PR3 was inhibited by three out of five IgG preparations purified from c-ANCA-positive sera of WG patients. PR3-mediated cytolysis was inhibited by each of the c-ANCA+IgG preparations and also to a limited extent by control IgG, suggesting a partial nonspecific stabilization of the endothelial cells. These studies provide evidence that besides elastase, PR3 also plays an important role in the PMN-mediated endothelial cell damage.

Role of theta toxin, a sulfhydryl-activated cytolysin, in the pathogenesis of clostridial gas gangrene.

Clostridial infections cause a wide variety of dramatic infections and intoxications. In each case the major virulence factors are extracellular toxins. Clostridium perfringens produces potent exotoxins, which are its major virulence factors. theta Toxin, a thiol-activated cytolysin, causes the clear zone of hemolysis around colonies on blood-agar plates, suppresses myocardial contractility ex vivo, and induces shock within 1 to 2 hours in vivo. Low concentrations of theta toxin induce priming and degranulation of polymorphonuclear leukocytes (PMNs) and functional up-regulation of PMN-dependent adherence molecules such as the integrin CD11/CD18, whereas higher concentrations are cytotoxic. Similarly, theta toxin causes concentration- and time-dependent induction of endothelial cell synthesis of platelet-activating factor, a potent proinflammatory lipid autocoid that mediates endothelial cell-dependent adherence of PMNs. These data suggest that theta toxin in high concentrations is a potent cytolysin and promotes direct vascular injury at the site of infection. At lower concentrations theta toxin activates PMNs and endothelial cells, and in so doing promotes vascular injury distally by activating adherence mechanisms. The rapid tissue necrosis associated with C. perfringens infection may be related to progressive vascular compromise orchestrated by dysregulated host-cell responses induced by theta toxin.

Chemotaxis and degranulation of polymorphonuclear leukocytes in the presence of sulfide.

In polymicrobial infections such as periodontal disease, the polymorphonuclear leukocytes (PMN) may have to work in the absence of oxygen and in the presence of significant levels of hydrogen sulfide. There are conflicting results reported on the chemotactic capacity of PMN under anaerobic conditions. It is not known whether PMN are able to migrate and release the contents of their granules in the presence of sulfide. PMN were exposed to various levels of sulfide and their chemotaxis and degranulation were studied when they were stimulated with N-formyl-methionyl-leucyl-phenylalanine or zymosan-activated serum. Chemotaxis was evaluated with the agarose method. The release of granule markers, lactoferrin and myeloperoxidase, was evaluated with enzyme-linked immunosorbent assay. PMN had similar capacity for chemotaxis under aerobic and anaerobic conditions. The migration of PMN was only to a minor extent inhibited by 1-2 mM sulfide. The release of lactoferrin and myeloperoxidase was the same under aerobic and anaerobic conditions and was not significantly influenced by sulfide. PMN seem to be very well suited to defend the tissue against bacteria under the harsh conditions prevailing in the periodontal pocket.

The interleukin-1 receptor antagonist influences interleukin-1 effects in rat and mouse

In this work we have focused on the ability of interleukin-1 to induce an acute phase protein response and a degranulation of polymorphonuclear leukocytes in vivo. The capacity of the interleukin-1 receptor antagonist to influence these events was also investigated. It was shown that interleukin-1 induced an acute phase protein response in rats and mice. In rats α2-macroglubolin levels were increased in plasma after an interleukin-1 injection whereas α1-inhibitor-3 decreased in plasma. In the mice plasma amyloid P was increased. The interleukin-1 receptor antagonist blocked the increase of α2-macroglobulin and plasma amyloid P in a dose dependent way while the effect on the α1-inhibitor-3 decrease was less pronounced. Interleukin-1 led to polymorphonuclear leukocyte degranulation in vivo as measured by increased cathepsin G plasma levels. The interleukin-1 receptor antagonist could influence the early phase of this degranulation.

FK-506 and cyclosporin a: Selective inhibition of calcium ionophore-induced polymorphonuclear leukocyte degranulation

This paper investigates the abilities of FK-506 and cyclosporin A (CsA) to inhibit human polymorphonuclear leukocyte (PMNL) degranulation. PMNLs, purified from human blood, were stimulated in vitro with A23187, ionomycin, the complement derived peptide C5a, formyl-methionylleucinylphenylalanine (FMLP) or phorbol myristate acetate (PMA). Degranulation was assessed by measuring the release of either lactoferrin or N- acetyl-β- d-glucosaminidase (NAG). Both FK-506 and CsA produced a concentration-related inhibition of degranulation induced by either A23187 or ionomycin but did not affect C5a-, FMLP- or PMA-induced deganulation. The ic 50 values for inhibition of degranulation (approximately 0.7 nM for FK-506 and 33.7 nM for CsA) are very close to the published values for inhibition of human T-cell proliferation. Removal of calcium from the incubation medium with ethyleneglycolbis(aminoethylether)tetra-acetate (EGTA) totally inhibited calcium ionophore-induced degranulation but had no effect against C5a-, FMLP- or PMA-induced degranulation. Preincubation of PMNLs with actinomycin D or cycloheximide did not affect either A23187- or PMA-induced degranulation. Non-immunosuppressive analogs of CsA were ineffective at inhibiting degranulation. Rapamycin, a macrolide structurally related to FK-506, did not inhibit degranulation but it did antagonize the inhibition produced by FK-506. Given the similar profiles of activity of FK-506 and CsA in neutrophils and T cells, we conclude that similar activation or signal transduction pathways may be present in both T cells and neutrophils. Because A23187-induced PMNL degranulation was not sensitive to either actinomycin D or cycloheximide, it is apparent that the signal transduction pathways ultimately control different cellular functions.

Polymorphonuclear leukocyte degranulation with exposure to polymethylmethacrylate nanoparticles

Polymethylmethacrylate (PMMA) is clinically employed in a wide range of orthopaedic procedures. The etiology of the inflammatory reaction of recipient tissues to PMMA remains unresolved. Classically, polymorphonuclear leukocytes (PMNs) release cytoplasmic lysosomal granules when exposed to a variety of proinflammatory stimuli. Such degranulation contributes, and partially defines, the local tissue reaction to this foreign material. In the present investigation, PMMA particles (50-60 nm) were mixed with human PMNs, and the amount of lactate dehydrogenase, lysozyme, and beta-glucuronidase released from the cells was quantitated. In all cases, a dose-dependent increase in degranulation followed the addition of increasing amounts of PMMA to the PMNs. In addition, the migration of PMNs was diminished in a dose-dependent manner with exposure to increasing amounts of the cement. These results suggested that PMMA stimulates the release of leukocyte lysosomal contents and alters the migration characteristics of these cells in a manner that is consistent with the local inflammatory reaction to this cement.

Inhibition of myeloperoxidase by synovial fluid and serum.

An inhibitor of myeloperoxidase has been identified in the synovial fluids and sera from patients with rheumatoid arthritis and sera from normal subjects. Initially, these fluids were found to inhibit stimulus induced degranulation of polymorphonuclear leucocytes independently of the stimulating agent. Subsequently, the fluids were shown to inhibit the released enzyme rather than the degranulation response of polymorphonuclear leucocytes. Both rheumatoid and normal serum samples contained high concentrations of the inhibitor but the concentrations were lower in rheumatoid synovial fluids. The inhibitory activity seemed to be specific for peroxidase as the fluids did not inhibit beta-glucuronidase activity. A protein of relative molecular mass (Mr) 150 kd was purified from synovial fluid by affinity chromatography on myeloperoxidase-Sepharose. It is concluded that serum and synovial fluid contain a novel myeloperoxidase inhibitor, which acts by binding to myeloperoxidase and thereby prevents myeloperoxidase releasing oxidative products in serum.

Release of proteinases from stimulated polymorphonuclear leukocytes

The secretion of matrix-degrading proteinases and protein components involved in the production of cytotoxic metabolites is an important step in the sequence of defense reactions executed by polymorphonuclear leukocytes (PMNL) in response to stimulation. In the present report, we have analyzed degranulation of PMNL stimulated either with soluble synthetic peptides fLeu-Phe (fMet, formylmethionyl), or fAhx-Leu-Phe-Ahx-Tyr-Phe (Ahx, aminohexyl) which trigger chemotaxis and degranulation, or with opsonized zymosan which induces phagocytosis. The release of elastase, myeloperoxidase and lactoferrin-containing granules was not at all or only slightly (less than 6%) induced either by fAhx-Leu-Phe-Ahx-Tyr-Leu or by zymosan particles. In contrast, type-I collagenase and gelatinase were secreted in significant amounts after treatment with these agents. The disruption of microfilaments by cytochalasin B and subsequent stimulation of PMNL with the formyl-peptide led to the secretion of elastase, myeloperoxidase and lactoferrin, and enhanced the release of gelatinase. Disruption of microtubules by incubation with colcemid resulted in inhibition of fAhx-Leu-Phe-Ahx-Thyr-Leu and fAhx-Leu-Phe-Ahx-Tyr-Leu/cytochalasin-B-induced granule release. Furthermore, we found different patterns of enzyme distribution after fractionation by centrifugation: most (greater than 90%) type-I collagenase and gelatinase was measured in the supernatant whereas 60-90% of elastase, myeloperoxidase and lactoferrin had partitioned into the cytoskeleton-containing pellet. Our results suggest that the two main types of secretory vesicles identified in PMNL (specific and azurophilic granules) consist of subpopulations. The differential association of the various types of granules with cytoskeletal elements may serve to control their sequential discharge.

Plasma Lactoferrin and Elastase in Healthy Pregnant Women and Pregnancy Associated Toxaemia

SummaryIn order to investigate the influence of pregnancy on the activation and degranulation of polymorphonuclear leucocytes in vivo, lactoferrin levels and neutrophil elastase bound to α1-proteinase inhibitor were determined in plasma samples of pregnant women and patients with pregnancy induced hypertension. The median plasma lactoferrin and α1-proteinase inhibitor bound elastase levels were higher in pregnant than in non-pregnant females (300 versus 200 ng/ml for lactoferrin and 92 versus 70 ng/ml for the proteinase inhibitor elastase; P < 0.001 in each case). The median plasma levels in pregnancy hypertension were higher than in normal pregnancy (670 versus 300 ng/ml for lactoferrin and 180 versus 92 ng/ml for the proteinase inhibitor elastase; P < 0.001 in each case). These data indicate that there is activation and degranulation of polymorphonuclear leucocytes in pregnancy induced hypertension.

Increased intracellular levels of β-glucuronidase in polymorphonuclear leucocytes from humans with rapidly progressive periodontitis

The tissue destruction resulting from release of lysosomal enzymes by exocytosis and degranulation of polymorphonuclear leucocytes in host gingiva may contribute significantly to periodontal diseases. In this investigation peripheral blood was obtained from healthy controls and otherwise healthy individuals with rapidly progressive periodontitis. Polymorphonuclear leucocytes were isolated and suspended in HBSS for subsequent in vitro FMLP challenge to induce degranulation. The supernatant was tested for β-glucuronidase. Polymorphonuclear leucocytes from patients with rapidly progressive periodontitis contained significantly higher absolute amounts of β-glucuronidase ( p < 0.001) and released greater amounts at various molarities of FMLP antigenic challenge ( p < 0.01). Such an increase in lysosomal enzyme activity may provide an enhanced potential for tissue destruction in this periodontal disease.

Evaluation of a New Polyamide Membrane (Polyflux 130) in High-Flux Dialysis

Removal of beta 2-microglobulin has become a major objective of dialysis therapy. The present study was performed to evaluate both compatibility and elimination capacity for beta 2-microglobulin of a newly developed high-flux polyamide membrane (Polyflux 130) during hemodialysis. The degree of leukopenia was moderate (-22%) and comparable with Polysulfone 600 (-25%). C3a desarg generation had a tendency to be lower with the Polyflux 130 membrane, and C5a desarg formation was identical with both types of membranes. As for degranulation of polymorphonuclear leukocytes, plasma elastase levels increased by 209% with Polyflux 130 and by 160% with Polysulfone 600 membranes. Likewise, plasma lactoferrin values rose during hemodialysis by 233% (Polyflux 130) and 160% (Polysulfone 600). The differences between membranes, however, were statistically not significant. There was a sharp drop in the serum levels of beta 2-microglobulin during dialysis with both membranes (Polyflux 130: -46%; Polysulfone 600: -48%). Accordingly, sieving coefficients were calculated to be 0.77 +/- 0.06 for Polyflux 130 and 0.80 +/- 0.06 for the Polysulfone 600 membrane. Both membranes were capable to remove large quantities of beta 2-microglobulin, amounting to 235 +/- 11 and 250 +/- 10 mg/4 h of dialysis for Polyflux 130 and Polysulfone 600, respectively.

Enzymes involved in the biosynthesis of leukotriene B4

Ten years have elapsed since the discovery and structural elucidation of the leukotriene compounds (1-5). The leukotrienes constitute a group of potent biologically active arachidonic acid-derived metabolites which are implicated as mediators of immediate hypersensitivity reactions and inflammation. They were first discovered in leukocytes and were determined to contain a conjugated triene structure, thus the derivation of their name (6). The cysteinyl-containing leukotrienes (LTC,, LTD4, and LTE,),' which together make up the slow reacting substance of anaphylaxis, are synthesized primarily by eosinophils, mast cells, and macrophages. They stimulate contraction of various smooth muscle cells, promote bronchial mucous secretion, and induce extravasation of plasma proteins by increasing microvascular permeability. Leukotriene B, (LTB,), synthesized predominantly by neutrophils, is capable of stimulating circulating leukocytes to adhere to the vascular endothelium and induces extravasation and chemotaxis of polymorphonuclear leukocytes in nanomolar concentrations. At higher concentrations, LTBI induces polymorphonuclear leukocyte degranulation, superoxide generation, and can augment natural killer cell activity. Several reviews on the structure, biosynthesis, and biological actions of the leukotrienes have been written (7-13). It is the aim of the present review to concentrate on the advances made in recent years, primarily through molecular biology studies, on the reaction pathway leading to production of LTB,. 5-Lipoxygenase

Effects of cytochalasin B, N-formyl peptide and plasma on polarisation, zeiosis (blebbing) and degranulation of polymorphonuclear leukocytes in suspension

The effects were studied of cytochalasin B and N-formyl peptide (FMLP) in various concentrations on the morphology and degranulation (release of the granule contents lysozyme and β-glucuronidase) of polymorphonuclear leukocytes (PMN) suspended in either Hanks' solution or100% fresh heparinised plasma. PMN in low concentrations of FMLP in Hanks' solution or in plasma alone showed “long” polarisation and did not degranulate. Cytochalasin B caused the PMN in low concentrations of FMLP or in plasma to become spherical, but no degranulation of the cells occurred. High concentrations of FMLP in Hanks' solution induced “short” polarisation of PMN with slight degranulation of the cells. Cytochalasin B together with high concentrations of FMLP in Hanks' solution induced zeiosis (“blebbing”) and marked degranulation of the cells. However, cytochalasin B and high concentrations of FMLP in plasma caused PMN to exhibit “short” polarised morphology and markedly degranulate. These results suggest that degranulation of PMN can be associated with either the “short” polarised shape of the cells or zeiosis, but not the “long” polarised form. Furthermore, the results indicate that plasma, although capable of causing “long” polarisation of the cells, inhibits zeiosis without affecting the degranulation of the cells induced by cytochalasin B.

慢性肝炎患者における末梢静脈血中ロイコトリエンについて

The leukotrienes are derived from arachidonic acid via a lipoxigenase pathway and are potent mediators of inflammation and allergy. Leukotriene B4 (LTB4) not only causes chemotaxis, chemokinesis and degranulation of polymorphonuclear leukocytes but also involves in the enhanced production of interleukin 1 from macrophages, interleukin 2 and interferon-gamma production from T lymphocytes and activation of natural killer (NK) cells. Leukotriene C4 (LTC4) enhances vascular permeability and induces tissue edema. Recently, it is suggested that leukotrienes may be key mediators in inflammatory liver diseases. In this study, to clarify the relation of leukotrienes to liver injury, we have examined the blood levels of LTB4 and LTC4 in chronic hepatitis.Leukotrienes were assayed using with the combination of technique of reverse-phase high-performance liquid chromatography and radioimmunoassay.The following results were obtained. (a) The blood level of LTB4 in chronic hepatitis was significantly higher than control group. (b) No significant difference of blood level of LTC4 between chronic hepatitis and control group was obtained.These results suggested that increased levels of LTB4 may be involved in the inflammatory and immunologic events in liver tissue in chronic hepatitis.

Effect of immunosuppression on the release of main granulocyte components: in vivo and in vitro studies.

In operative trauma or severe inflammatory responses, polymorphonuclear leukocytes release lysosomal proteinases extracellularly and into the circulation (Duswald et al., 1985). Immediately after surgery a decrease of elastase in complex with α1-proteinase inhibitor (Eα1PI) is observed due to the elimination of the infection focus (Jochum et al., 1984). During hemodialysis treatment there is also an increase of E- α1PI (Hörl et al., 1983; Hörl and Heidland 1984) depending on the membrane material of the dialyzer used (Horl et al., 1985a and b). There was also demonstrated that polymorphonuclear leukocytes release myeloperoxidase and lactoferrin during hemodialysis treatment (Hörl et al., 1986). Corticosteroids can stabilize membranes, inhibit locomation, phagocytosis and degranulation of polymorphonuclear leukocytes (Smolen and Weissmann 1978; Dunham et al., 1977). In the present study we evaluated plasma levels of main granulocyte components of patients following cadaveric renal transplantation. The effect of different immune suppressive drugs on the release of main granulocyte constituents was investigated in vitro and also during hemodialysis.KeywordsPolymorphonuclear LeukocyteHemodialysis TreatmentSpecific GranuleHuman Polymorphonuclear LeukocyteOperative TraumaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Effect of an inhibitor of protein kinase C on human polymorphonuclear leukocyte degranulation

The protein kinase C inhibitor C-I reduced superoxide production by human neutrophils in response to phorbol myristate acetate by > 50%. In contrast to its effects in oxidative metabolism, 100 uM C-I caused minimal inhibition (5–18%) of lysozyme release in response to phorbol myristate acetate. Enzyme release produced by the formylated oligopeptide FMLP was enhanced by 23–54% in neutrophils pretreated with 100 uM C-I. These findings suggest that protein kinase C activation is not required for phorbol myristate acetate induced enzyme release. Enhancement of FMLP stimulated degranulation by C-I suggests that protein kinase C activation may have inhibitory effects on the release of granule enzymes by human neutrophils.

Leukotriene B5 is formed in human neutrophils after dietary supplementation with icosapentaenoic acid.

Incorporation and conversion of icosapentaenoic acid (20:5, n - 3) by human polymorphonuclear leukocytes were studied in volunteers (n = 6) ingesting a normal Western diet supplemented with icosapentaenoic acid (approximately equal to 4 g daily). Ingestion of icosapentaenoic acid leads to formation of biologically less active leukotriene B5 (LTB5) from polymorphonuclear leukocytes (PMNL) stimulated with ionophore A23187. LTB5 was identified on HPLC by UV absorption and by GC/MS and showed a behavior identical to that of in vitro synthesized LTB5 produced by incubation of human PMNL with icosapentaenoic acid. The ratio of icosapentaenoic acid/arachidonic acid (20:4, n - 6) in cellular phospholipids increased from 0.045 during control to 0.28 after the supplemented period. LTB5 increased from undetectable values to 70.2 +/- 18.7 pmol of LTB5 per 10(7) PMNL during the experimental period. Synthesis of LTB4 did not change significantly (control, 218.8 +/- 89.1; icosapentaenoic acid-enriched diet, 253.6 +/- 18.7 pmol per 10(7) PMNL). The ratio of LTB4/LTB5 corresponded to the ratio of arachidonic acid/icosapentaenoic acid in PMNL phospholipids. Our findings prove that LTB5, which is 10 to 30 times less potent than LTB4 to cause aggregation, chemotaxis, and degranulation of PMNL, can be formed in vivo in man after dietary icosapentaenoic acid. This may modify the contribution of leukotrienes in processes in which these metabolites are of pathogenetic relevance.

Alcohol and the integrity of the pancreas.

Alcohol may affect the integrity of the pancreatic parenchyma, as seen in alcoholic pancreatitis, some cases of chronic alcoholism without clinical pancreatitis, and experimental studies. The composition of pancreatic juice may reflect some of these changes. One type of parenchymal alteration is the loss of differentiative features of acinar cells, so that they take on the characteristics of ductular cells. Concomitant fibrosis completes the formation of the tubular complexes found in association with alcoholic chronic pancreatitis. Sustained alcohol intake may produce the accumulation of lipid droplets in parenchymal cells, some of which may be shown to be within the rough endoplasmic reticulum of acinar cells. Epithelial cells may undergo mucous metaplasia. The epithelial-basal lamina barrier frequently is breached in the area of intraluminal aggregates, with or without obvious inflammation in the immediate area. Loss of barrier function may lead to interaction among components of the external compartment (lumen) and the internal compartment (stroma). Increased levels of blood proteins and glycosaminoglycans in the juice, enzyme activation, fibrin formation, and complement activation are potential consequences of barrier loss. Increased lactoferrin levels could result in part from the activity and degranulation of polymorphonuclear leukocytes.

Leukotriene B 4 and its action with a free-radical-generating system

The concentration of Leukotriene B 4 (LTB 4) demonstrated in early inflammation has been shown to induce leukocyte aggregation, chemotaxis and degranulation of polymorphonuclear leukocytes (PMN) in vitro . N-f-Met. Leu-Phe, a potent chemotactic factor, has been shown to activate neutrophils to produce chemiluminescence and produce superoxide radicals. The characteristics of the LTB 4-induced degranulation of rabbit neutrophils are strikingly similar to those of the chemotactic factors. Thiols, and in partiicular glutathione, have been shown to have a marked inhibitory effect in clinical assays of superoxide dismutase (SOD) activity, using reactions which are supposedly specific for the superoxide ion. SOD is most frequently assessed by coupling a generator of O 2 − with an indicating scavenger for the radical. The enzyme then competes with the scavenger for the available O 2 − and inhibits the processes being observed, thus, the inhibition serves as a basis for estimation of SOD activity. A method proposed by Misra and Fridovich for the estimation of SOD activity is based on the photo-oxidation of dianisidine sensitised by riboflavin. This assay can be used to classify compounds as either SOD-like or glutathione-like. With a small quantity if LTB 4 and LTD 4, we obtained preliminary results for their effect on the assay (Table 1). They appear to be glutathione-like, i.e., reactive with the free-radical-generating system in preference to a specific reaction with O 2 − and are only slightly less effective than glutathione. Although our results are preliminary it is clear that the leukotrienes are effective as radical scavengers in this reaction. Further studies with two prostaglandis (products of the cycloxygenase pathway) will also be presented.