Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Experiments were designed to analyze the effects of ouabain on the actions of exogenous arachidonic acid on endothelial and vascular smooth muscle cells. Rings or strips were prepared from left circumflex canine coronary arteries and suspended for isometric tension recording in organ chambers filled with oxygenated modified Krebs-Ringer-bicarbonate solution. During contractions evoked by prostaglandin F2 alpha, arachidonic acid caused relaxations both in the presence and the absence of endothelium. However, removal of the endothelium reduced its inhibitory action. Indomethacin prevented the relaxations in rings without endothelium, but did not affect the response to high doses (10(-6) to 10(-5) M) of arachidonic acid in preparations with endothelium. The inhibitor of lipoxygenase, nordihydroguaiaretic acid, had no effect on the inhibitory responses to arachidonic acid in rings with or without endothelium. Ouabain abolished both the endothelium-dependent and the direct relaxations to arachidonic acid. Endothelium-dependent relaxations in response to oleic acid, elaidic acid, adenosine diphosphate and thrombin were not affected by ouabain. In the presence of indomethacin, coronary artery strips without endothelium were relaxed by arachidonic acid only when layered (intimal surface against intimal surface) with a longitudinal strip with endothelium. In layered preparations, treatment of the intact longitudinal strip with ouabain before layering prevented the relaxation, whereas pretreatment of the strip without endothelium had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ouabain inhibits endothelium-dependent relaxations to arachidonic acid in canine coronary arteries. 393 Jul

We have previously reported that endothelial cells synthesize a cytosol-associated, lipoxygenase-derived metabolite, LOX, which acts as a chemorepellant and, in so doing, maintains the vessel wall thromboresistance. In this study we demonstrate that LOX is a 13-hydroxylinoleic acid (13-OH-18:2) derived from linoleic acid and identical to 13-hydroxy-9-cis,11-trans-octadecadienoic acid, as measured by both reverse phase high pressure liquid chromatography and gas chromatography/mass spectrometry. In addition, we demonstrate that 13-OH-18:2 is produced in significantly greater quantities by endothelial cells than by smooth muscle cels or by fibroblasts. Furthermore, we demonstrate that 13-OH-18:2 is produced in microgram amounts under basal conditions and is decreased by thrombin, calcium ionophore, and trypsin stimulation. And finally, we demonstrate that endothelial cells do not synthesize any significant amounts of lipoxygenase-derived arachidonic acid metabolites either under basal or stimulated conditions unless exogenous arachidonic acid is added. These observations indicate that the major lipoxygenase-derived, chemorepellant metabolite produced by the endothelial is 13-hydroxy-9-cis,11-trans-octadecadienoic acid.
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PMID:13-Hydroxyoctadecadienoic acid is the vessel wall chemorepellant factor, LOX. 393 68

The platelet aggregation that occurred in whole blood in response to several aggregating agents (collagen, arachidonic acid, adenosine diphosphate, adrenaline and thrombin) was measured using an Ultra-Flo 100 Whole Blood Platelet Counter. The amounts of thromboxane B2 produced were measured by radioimmunoassay. The effects of various inhibitors of thromboxane synthesis and the effects of apyrase, an enzyme that destroys adenosine diphosphate, were determined. Platelet aggregation was always accompanied by the production of thromboxane B2, and the amounts produced depended on the nature and concentration of the aggregating agent used. The various inhibitors of thromboxane synthesis--aspirin and flurbiprofen (cyclo-oxygenase inhibitors), BW755C (a cyclo-oxygenase and lipoxygenase inhibitor) and dazoxiben (a selective thromboxane synthase inhibitor)--did not markedly inhibit aggregation. Results obtained using apyrase showed that adenosine diphosphate contributed to the aggregation process, and that its role must be acknowledged when devising means of inhibiting platelet aggregation in vivo.
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PMID:Platelet aggregation in whole blood: the role of thromboxane A2 and adenosine diphosphate. 393 61

The activity of alpha-thrombin and chemically modified derivatives of this enzyme in stimulating cGMP formation in murine neuroblastoma clone N1E-115 cells is reported. The rank order potency of the compounds falls into three classes: 1) alpha-thrombin is the most potent and effective; 2) the catalytically active enzymes gamma-thrombin, trypsin, and nitro-alpha-thrombin are approximately 50-fold less potent than alpha-thrombin; and 3) active site blocked derivatives of alpha-thrombin are 100 to 1000-fold less potent than alpha-thrombin. Native alpha-thrombin consistently produces the most effective response, usually 1.5 to 3-fold greater than any of the other compounds tested. Preincubation of cells with quinacrine, an inhibitor of phospholipase A2, or with the lipoxygenase inhibitors 5,8,11,14-eicosatetraynoic acid or nordihydroguaiaretic acid prior to thrombin challenge resulted in a concentration-dependent attenuation of the response. Indomethacin was without effect in modifying the response. These results suggest that thrombin stimulation of neuroblastoma cells involves the release of arachidonic acid and its metabolism by lipoxygenase. These results clearly demonstrate the activity of alpha-thrombin in stimulating a receptor-mediated response in cultured nerve cells. The results are discussed in relation to the interaction of endogenous alpha-thrombin with nerve cells following invasive trauma and to the possible presence of endogenous proteinases with a neurotransmitter-like function.
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PMID:Activation of cyclic nucleotide formation in murine neuroblastoma N1E-115 cells by modified human thrombins. 608 21

We studied interactions of human platelets and neutrophils with particular reference to the arachidonic acid pathway. Suspensions of [3H]arachidonate-labeled platelets and unlabeled neutrophils were stimulated with ionophore A23187. We detected several radioactive arachidonate metabolites, which are not produced by platelets alone. These included [3H]-labeled leukotriene B4 (LTB4), dihydroxy-eicosatetraeonic acid (DiHETE), and 5-hydroxy-eicosatetraenoic acid (5-HETE). DiHETE was formed when the platelet product [3H]12-HETE was added to ionophore-stimulated neutrophils. In addition, DiHETE was the major metabolite when [3H]5-HETE, a neutrophil arachidonate product, was added to stimulated platelets. We therefore suggest that upon stimulation, platelet-derived arachidonate can serve as precursor for the neutrophil-derived eicosanoids LTB4 and 5-HETE, and the platelet-derived product 12-HETE can be metabolized to DiHETE by stimulated human neutrophils. More recently we have shown that 12-HETE from thrombin-stimulated platelets can also be metabolized to a new product, 12,20-DiHETE, by unstimulated human neutrophils. It would appear that the platelet and neutrophil lipoxygenase pathways take part in cell-cell interactions--an observation that suggests a role for the neutrophils that are present in hemostatic plugs, thrombi, and inflammatory processes.
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PMID:Production of metabolic products of arachidonic acid during cell-cell interactions. 608 11

The mechanisms by which adenosine triphosphate, thrombin, and trypsin cause relaxation of vascular smooth muscle were investigated. Relaxation of the rat thoracic aorta with adenosine triphosphate, thrombin, and/or trypsin was associated with increased levels of cyclic guanosine monophosphate in both time- and concentration-dependent manners. Thrombin and trypsin did not alter cyclic adenosine monophosphate levels, whereas adenosine triphosphate increased cyclic adenosine monophosphate levels after significant relaxation occurred. Removal of the endothelium abolished adenosine triphosphate-, thrombin-, and trypsin-induced relaxation and the associated increased levels of cyclic nucleotides. Relaxation due to these agents was also inhibited by exposure to nordihydroguaiaretic acid, a lipoxygenase inhibitor, and eicosatetraynoic acid, a lipoxygenase and cyclooxygenase inhibitor. Indomethacin, a cyclooxygenase inhibitor, potentiated relaxation to these agents, whereas the increased levels of cyclic nucleotides due to adenosine triphosphate were unaltered. Bromophenacyl bromide, a phospholipase A2 inhibitor, decreased relaxation due to adenosine triphosphate, thrombin, and trypsin and the associated increased levels of cyclic nucleotides. Removal of extracellular calcium, which also presumably inhibits phospholipase A2, prevented the elevated levels of cyclic nucleotides and the inhibitory effects of adenosine triphosphate and trypsin on contraction. In contrast, sodium nitroprusside-induced relaxation and/or increased levels of cyclic guanosine monophosphate were unaltered by nordihydroguaiaretic acid, eicosatetraynoic acid, bromophenacyl bromide, and removal of extracellular calcium. After incubation of intact tissue with 32P-orthophosphate, the patterns of protein phosphorylation caused by adenosine triphosphate, thrombin, and trypsin were indistinguishable from those of acetylcholine, sodium nitroprusside and 8-bromo cyclic guanosine monophosphate. All these agents dephosphorylated myosin light chain. Thus, the present study supports the hypothesis that relaxation induced by adenosine triphosphate, thrombin, and trypsin is mediated through the formation of an endothelial factor which elevates cyclic guanosine monophosphate levels and causes cyclic guanosine monophosphate-dependent protein phosphorylation and dephosphorylation of myosin light chain.
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PMID:Mechanisms of adenosine triphosphate-, thrombin-, and trypsin-induced relaxation of rat thoracic aorta. 609 35

8,11,14-icosatrienoic (DHLA), 5,8,11,14,17-icosapentaenoic (EPA) acids (the monoenoic and trienoic prostaglandin precursors, respectively) and 5,8,11-icosatrienoic acid (20:3n-9) were pre-coated onto albumin and then incorporated into platelet lipids. Around 80% of the total incorporation concerned their acylation into phospholipids and a few percentage was oxygenated through the cyclooxygenase and/or lipoxygenase pathways, simulating therefore the in vivo situation. Such modified platelets normally oxygenated exogenous arachidonic acid (AA) while (only when enriched with DHLA or EPA) they produced less oxygenated derivatives of AA under thrombin stimulation. This indicates that endogenous AA liberation was decreased in both DHLA and EPA-rich platelets, which might be related to the formation of inhibitory prostaglandins from these polyunsaturated fatty acids.
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PMID:Uptake and effect on arachidonic acid oxygenation of some icosaenoic acids in human platelets. 609 36

Washed rabbit platelets stimulated with platelet-activating factor, thrombin, or arachidonic acid, released a slow-reacting substance (SRS), whereas platelets aggregated by adenosine diphosphate did not. Production of platelet-derived SRS was neither affected by indomethacin nor aspirin but was reduced by large doses of eicosatetraynoic acid, an inhibitor of the cyclo-oxygenase and lipoxygenase. L-cysteine enhanced markedly the release of SRS from platelets. This SRS activity, which was antagonized by FPL 55712 and inactivated by arylsulfatase, followed the same elution pattern on Amberlite, silicic acid, and reverse phase high-pressure liquid chromatography columns as that described for the SRS from other origins. SRS activity released from platelets preincubated with [14C]arachidonic acid exhibited the same retention time as radioactivity in reverse phase high-pressure liquid chromatography. The release of a SRS from platelets is consistent with their implication in the pathogenesis of asthma and other lung diseases.
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PMID:Release of a slow-reacting substance from rabbit platelets. 611 24

The biochemistry of platelets from two unrelated patients with the gray platelet syndrome, a deficiency of platelet alpha-granules, has been evaluated. Ultrastructural studies of their platelets revealed the number of alpha-granules to be less than 15% of normal, whereas the number of dense bodies was within normal limits. Platelets from both patients had severe deficiencies of platelet factor 4 and beta-thromboglobulin (less than 10% of normal). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a marked deficiency of thrombin-sensitive protein in both patients. Analysis of the platelet-derived growth factor in one patient showed it was also markedly reduced. Levels of lysosomal enzymes, adenine nucleotides, serotonin, and catalase, and conversion of arachidonic acid by the lipoxygenase and cyclo-oxygenase enzymes, were within normal limits. The results provide important evidence to define the contents of alpha-granules and to differentiate these contents from the contents of lysosomal granules, dense bodies, and peroxisomes. Functional studies of these platelets showed deficiencies in ADP, thrombin, and collagen aggregation. The results suggest that alpha-granules or their contents make a contribution to normal platelet aggregation.
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PMID:Biochemical studies of two patients with the gray platelet syndrome. Selective deficiency of platelet alpha granules. 615 48

Although arachidonic acid causes rabbit platelet aggregation and the release of granule contents in suspensions of washed platelets when used in concentrations of approximately 50-300 microM, higher concentrations (500 microM) cause neither aggregation nor release. Suspensions of platelets from rabbits wee exposed to arachidonic acid (250 microM) for 15 min, allowed to recover in the presence of PGE1 for 30 min, washed, and resuspended; in some experiments, the platelets were treated with aspirin before being exposed to arachidonic acid. Aggregation of platelets pretreated with arachidonic acid was inhibited in response to ADP; this effect was greater with the non-aspirin-treated platelets and persisted for at least 4 hr after resuspension. The association of 125I-fibrinogen with the platelets as a result of ADP stimulation was also inhibited. Aggregation and release of granule contents in response to collagen and low concentrations of thrombin was inhibited, but the inhibition could be overcome by higher concentrations. Thrombin induced further release of granule contents from platelets exposed to arachidonic acid without pretreatment with aspirin. Platelets that had been exposed to arachidonic acid, either with or without pretreatment with aspirin, did not aggregate or undergo further release upon stimulation with arachidonic acid after they were washed and resuspended. Inhibition of the lipoxygenase pathway with eicosatetraynoic acid (ETYA) or nordihydroguaiaretic acid (NDGA) did not affect the inhibition caused by arachidonic acid, so it is unlikely that a product of this pathway is responsible for the inhibition. Mixing experiments indicated that the pretreated platelets did not form a thromboxane-A2-like activity, and that they were unresponsive to aggregation and release induced by products formed from arachidonic acid. Experiments with 3H-arachidonic acid showed that after 45 min of incubation with platelets, only 1.1% of the 3H-arachidonic acid remained as free arachidonic acid in the platelets. Although cyclic-AMP was slightly increased 1 min after the addition of arachidonic acid, the cyclic-AMP concentration was the same as that of control platelets after the platelets were washed and resuspended, indicating that increased cyclic-AMP is not likely to be responsible for the persistent inhibitory effect. Thus, the inhibitory effect of pretreatment with arachidonic acid is a general effect on responses to a variety of aggregating agents that act through different mechanisms, and the inhibition is not related to thromboxane-A2 formation. The possibility of membrane perturbation resulting in the unavailability of receptors may explain the persistent inhibitory effect, but the responsible reactions have not been identified.
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PMID:The inhibitory effects of exogenous arachidonic acid on rabbit platelet aggregation and the release reaction. 628 42


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