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)

Human umbilical vein endothelial cells were found to contain adrenic acid (22:4) in their cellular lipids. Since this fatty acid may be metabolized by cyclooxygenase in the kidney, the metabolism of adrenic acid was studied in endothelial cell cultures. [14C]Adrenic acid was metabolized to several more polar metabolites. Two of these metabolites co-migrated on HPLC with 1 alpha,1 beta-dihomo-8-ketoprostaglandin F1 alpha (the metabolite of 1 alpha, 1 beta-dihomoprostaglandin I2) and 1 alpha,1 beta-dihomoprostaglandin E2. Indomethacin (10(-5) M) inhibited the synthesis of these metabolites. When cells were treated with adrenic acid (3 X 10(-5) M), a peak that co-migrated with dihomo-8-ketoprostaglandin F1 alpha was detected by radioimmunoassay using an antiserum directed against 6-ketoprostaglandin F1 alpha. The presence of dihomo-8-ketoprostaglandin F1 alpha was confirmed by gas chromatography-mass spectrometry. Immunoreactive peaks that co-migrated with dihomoprostaglandins E2 and F2 alpha were identified with antisera against prostaglandin E2 and prostaglandin F2 alpha, respectively. [14C]Arachidonic acid was metabolized to [14C]prostaglandin F2 alpha, 6-keto[14C]prostaglandin F1 alpha, and [14C]prostaglandin E2. Similar results were found with unlabelled arachidonic acid using specific antisera. When the two fatty acids were combined, adrenic acid reduced the metabolism of arachidonic acid. The culture media from endothelial cells inhibited thrombin-induced platelet aggregation, an effect blocked by aspirin. The inhibitory activity of the media was enhanced when arachidonic acid was added to the cells, but it was reduced by adrenic acid. Both prostaglandin I2 and dihomoprostaglandin I2 inhibited platelet aggregation, but prostaglandin I2 was 100-times more potent. We conclude that adrenic acid is metabolized in human endothelial cells to 1 alpha, 1 beta-dihomoprostaglandins and can compete with endogenous arachidonic acid for conversion by cyclooxygenase. These findings suggest that adrenic acid may reduce the formation of prostaglandin I2 by the blood vessel.
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PMID:Synthesis of dihomoprostaglandins from adrenic acid (7,10,13,16-docosatetraenoic acid) by human endothelial cells. 393 86

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

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

The present study was designed to determine whether interference with the metabolism of arachidonic acid or the entry of extracellular calcium affects the responses of the canine saphenous vein to acetylcholine, potassium or norepinephrine. Rings of canine saphenous vein, with or without endothelium, were suspended in organ chambers filled with physiological salt solution and set at their optimal length for isometric tension recording. Removal of the endothelium, confirmed by the absence of the characteristic relaxation induced by thrombin in intact rings, did not affect concentration-response curves to acetylcholine or norepinephrine. The cyclooxygenase inhibitor, indomethacin, augmented the response to acetylcholine. This effect was comparable in rings with and without endothelium and in rings pretreated with phentolamine. Indomethacin did not alter the response to norepinephrine but augmented that to potassium. Similar results were obtained with the cyclooxygenase inhibitors, acetylsalicylic acid and meclofenamate. The antioxidant and lipoxygenase inhibitor nordihydroguaiaretic acid and the cyclooxygenase/lipoxygenase inhibitor phenidone blocked the ability of indomethacin to augment acetylcholine- and potassium-induced contractions. Arachidonic acid-induced contractions were not blocked by indomethacin but were inhibited by nordihydroguaiaretic acid, phenidone and the calcium entry blockers diltiazem and nimodipine. Diltiazem and nimodipine inhibited responses to potassium and acetylcholine without affecting those to norepinephrine. The augmentation by indomethacin of potassium- and acetylcholine-evoked contractions was inhibited by diltiazem and nimodipine. In rings of femoral artery denuded of endothelium, indomethacin had no effect on the responses to acetylcholine, norepinephrine or potassium. These results suggest that, in the canine saphenous vein but not in the femoral artery, activation of the lipoxygenase pathway for the metabolism of arachidonic acid augments preferentially contractions which depend upon the entry of extracellular calcium.
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PMID:Effects of inhibitors of arachidonic acid metabolism and calcium entry on responses to acetylcholine, potassium and norepinephrine in the isolated canine saphenous vein. 640 42

The effects of parathyroid hormone (PTH), dihydroxycholecalciferol (1,25-(OH)2 D3), thrombin, epidermal growth factor (EGF) and 12-o-tetradecanoylphorbol-13-acetate (PMA) on the biosynthesis and release of arachidonic acid metabolites were studied in primary cultures of osteoblast-like cells isolated from 18-day-old chick embryo calvaria. Cells were labelled with (14C)-arachidonic acid for 30 h. The radioactive eicosanoids were extracted from the cell culture media after a further 30 h stimulation period and analysed on a PRP-1 column by HPLC. The radioactive products were characterized by co-elution of (3H) standard prostanoids. Osteoblasts showed a basal release of the prostanoids 6-keto-PGF1 alpha, TXB2, PGF2 alpha, PGE2, PGD2 and PGB2, the latter being the most abundant one. Indomethacin (10(-5) M) effectively inhibited the basal release, but not that of an as yet unidentified compound. The release of prostanoids was stimulated by PTH (2 U/ml), thrombin (0.4 NIH/ml), EGF (50 ng/ml) and PMA (25 ng/ml), the latter being by far the most potent one. 1,25-(OH)2D3 was found to slightly inhibit the prostanoid release. These results indicate: (1) primary cultures of osteoblasts synthesize several prostaglandins, thromboxane B2 and one unidentified product. (2) the action on bone of PTH and the various drugs tested may be, at least partly, mediated by an increased prostaglandin production by osteoblasts. Clearly this does not apply to 1,25-(OH)2D3.
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PMID:Stimulation of arachidonic acid metabolism in primary cultures of osteoblast-like cells by hormones and drugs. 644 Nov 89

Effects of seven purified phospholipases A2 from the venoms of snakes (Naja naja atra, Trimeresurus mucrosquamatus and T. gramineus) and honey bee (Apis mellifera) on rabbit washed platelet suspension in the absence of bovine serum albumin have been studied. Only phospholipases A2 from N. n. atra, T. mucrosquamatus and A. mellifera venoms induced platelet aggregation with small amounts of 14C-serotonin release. They showed tachyphylaxis and also cross-tachyphylaxis in inducing platelet aggregation. The former two phospholipases A2 exhibited biphasic responses in which irreversible aggregations appeared at concentrations of 1-10 micrograms/ml. At higher concentrations, they elicited the reversible aggregation. Exogenous Ca2+ was essential to their activity. Indomethacin and EDTA completely abolished both phospholipase A2 induced platelet shape change and aggregation, while mepacrine, prostaglandin E1, verapamil and nitroprusside inhibited only the aggregation response. p-Bromophenacyl bromide-modified phospholipases A2, which almost completely lost enzymatic activity, failed to induce platelet aggregation. Phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol inhibited the phospholipase A2-induced platelet aggregation. These phospholipases A2 induced thromboxane B2 formation which was inhibited by EDTA and indomethacin, but not by prostaglandin E1. Pre-treatment of platelet suspension with phospholipase A2 from N. n. atra or A. mellifera venom (50 micrograms/ml) inhibited platelet aggregation induced by sodium arachidonate or collagen, but not that induced by thrombin or ionophore A-23187. Exogenous sodium arachidonate or lysophosphatidylcholine also showed unaltered inhibitory spectrum on platelet aggregation. It is concluded that phospholipases A2 induce platelet aggregation by virtue of their enzymatic activity, cleaving the membrane phospholipids resulting in arachidonic acid release and formation of thromboxane A2. On the other hand, the cleaved products, lysophosphatidylcholine, arachidonic acid or arachidonate metabolites (via lipoxygenase pathway) may be responsible for anti-platelet activity.
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PMID:Effect of the purified phospholipases A2 from snake and bee venoms on rabbit platelet function. 644 10

Epinephrine (1 microM) plus ADP (5 microM) induced serotonin release from human platelets although neither epinephrine nor ADP alone brought about such a release. During this release reaction, the phosphorylation of 40K-dalton protein was induced to an extent similar to that induced by 0.5 unit/ml thrombin. The amount of diglyceride (DG) produced by epinephrine plus ADP, however, was much smaller than that produced by thrombin. The reaction velocities of these reactions induced by epinephrine plus ADP were slower than those induced by thrombin. Epinephrine or ADP alone hardly produced any DG and induced 40K-dalton protein phosphorylation only slightly. Indomethacin (1 microgram/ml), a cyclooxygenase inhibitor, remarkably inhibited epinephrine plus ADP induced serotonin release, 40K-dalton protein phosphorylation and DG production although this agent had little effect on the same reactions induced by thrombin. These results suggest that prostaglandin endoperoxides or thromboxane A2 may be involved in serotonin release, 40K-dalton protein phosphorylation and DG production induced by epinephrine plus ADP.
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PMID:Protein phosphorylation and diglyceride production during serotonin release induced by epinephrine plus ADP in human platelets. 661 81

Intravascular coagulation in the rat kidney was induced by intravenous infusion of thrombin for 1 hr. The proximal tubular free-flow (Pt) and stop-flow (Psf) pressures were measured by micropuncture. Some proximal tubules were obstructed with solid paraffin before infusion of thrombin. In certain rats saralasin or indomethacin was administered for 1 hr starting 30 min after the thrombin infusion, and the effect on the tubular pressures was studied. The deposition of fibrin in the glomeruli was examined by light and electron microscopy. Pt fell from 15 +/- 1 (SE) to 7 +/- 2 mm Hg (P less than 0.05) during the infusion of thrombin. After a brief period of increased pressure the Psf fell rapidly from 37 +/- 1 to 17 +/- 1 mm Hg (P less than 0.05). In the previously obstructed nephrons the pressure (Po) increased parallel to the increase in Psf but remained elevated after the infusion of thrombin, 54 +/- 2 mm Hg. The arterial blood pressure (Pa) increased from 119 +/- 2 to 138 +/- 3 mm Hg (P less than 0.05). Saralasin raised the Psf from 15 +/- 1 to 19 +/- 1 mm Hg (P less than 0.05) but had no effect on Pt, Po, or Pa. Indomethacin did not influence the pressures. Morphological examination revealed fibrin in all glomeruli of normal nephrons. In the previously obstructed nephrons the deposition of fibrin was almost totally prevented. The results suggest that glomerular filtration is important for deposition of fibrin in the kidney.
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PMID:Effect of renal tubular obstruction on stop-flow pressure and glomerular deposition of fibrin during intravascular coagulation in the rat. 664 5

Experiments were designed to determine the role of the endothelium in the responsiveness of the arterial wall to anoxia. Paired rings of canine femoral arteries were mounted for isometric tension recording in organ chambers filled with aerated Krebs-Ringer bicarbonate solution (37 degrees C). One ring served as control; in the other the intimal layer was removed mechanically. Anoxia was induced by gassing the organ chamber with 95% N2/5% CO2. In control rings anoxia augmented contractile responses to noradrenaline, KCl and BaCl2. On return to O2 the contractile responses were transiently depressed. Removal of the endothelium reduced the anoxic augmentation, but did not affect the post-anoxic inhibition. Indomethacin did not affect the response to anoxia. Anoxia abolished the endothelium-dependent inhibitory effect of acetylcholine and thrombin, reduced that of adenosine triphosphate, but augmented that of arachidonic acid. These experiments indicate that endothelial cells may contribute to anoxic facilitation of the responsiveness of the canine arterial wall.
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PMID:Anoxia and endothelium-dependent reactivity of the canine femoral artery. 687 96

Blood obtained from Mongolian gerbils (Meriones unguiculatus) by cardiac puncture was used to develop a method for preparing platelet suspensions suitable for biochemical and aggregometric studies. The aggregation responses of gerbil platelet suspensions to 10 microM adenosine diphosphate and to 0.2 U/mL thrombin were immediate and irreversible. In addition, thrombin produced a short lag period. Bovine acid-soluble collagen (1:800) produced a long lag period coupled with an irreversible aggregation. Indomethacin (10 microM) significantly depressed adenosine diphosphate--induced aggregation but had no effect on thrombin-induced aggregation. Indomethacin significantly prolonged the lag period and reduced the rate of collagen-induced aggregation. Our results strongly indicate that platelet suspensions from the Mongolian gerbil, an animal which is responsive to hypercholesterolemic diets, may be useful in studying dietary lipid factors which influence platelet aggregation.
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PMID:Platelet aggregation in platelet suspensions from Mongolian gerbils (Meriones unguiculatus). 688 86


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