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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ovulation, recurring every midcycle of the mammalian female and triggered by a surge of luteinizing hormone (LH) released from the pituitary, is an essential prerequisite for fertilization and subsequent embryonic development. Here we shall describe two of the biological components of the ovulatory response, cumulus expansion (frequently denoted as cumulus maturation) and the rupture of follicular wall, both crucial for the release of a fertilizable ovum. The role of a proteolytic cascade and its regulation by eicosanoids will be emphasized in relation to follicle rupture. The new data implicating cumulus maturation as an essential step for the release of the ovum and the apparent mediatory role of interleukin-1 in this process will be presented. LH/hCG stimulates, in the preovulatory follicles, a cascade of proteolytic enzymes, including plasminogen activator (PA), plasmin and matrix metalloproteinase 1 (MMP-1). These enzymes bring about the degradation of perifollicular matrix and, most notably, the decomposition of the meshwork of collagen fibers which provides the strength to follicular wall. Furthermore, pharmacological blockage of any of these enzymes resulted in inhibition of follicle rupture. LH/hCG stimulates, in addition, an increase in ovarian production of eicosanoids. These include prostaglandins, obtained from arachidonic acid via the cyclooxygenase pathway and leukotrienes, the products of lipoxygenase. Previous studies from our and other laboratories have demonstrated the ability of inhibitors of cyclooxygenase and of lipoxygenases to suppress ovulation in several mammalian species. MK-886, which inhibits the translocation of 5-lipoxygenase (5-LO) from the cytosol and its binding to the membranal 5-LO activating enzyme, suppressed dose-dependently follicular rupture from the treated ovary. Zymographic analysis of ovarian extracts from PMSG/hCG-stimulated rats revealed a band of collagenolytic activity at 52kD, corresponding to human MMP-1 and at 72kD, corresponding to human MMP-2. Both activities were markedly stimulated by administration of hCG and were significantly inhibited by indomethacin, NDGA or MK-886. Thus, eicosanoids seem to mediate LH stimulation of follicular collagenase. Interleukin-1 (IL-1) has been recently implicated in ovulation. The ability of an IL-1 receptor antagonist (ra) to block ovulation in vivo and in vitro has been demonstrated recently. Morphological examination of the ovulatory follicles failing to ovulate suggests that this effect is exerted by inhibiting cumulus oophorus expansion and detachment from mural granulosa cells. In vitro, IL-1ra attenuated the action of hCG and FSH on cumulus expansion and follicular hyaluronic acid synthesis. Thus, IL-1 seems to mediate and/or facilitate gonadotropin action on cumulus expansion, and hence on ovulation.
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PMID:Ovulation as a tissue remodelling process. Proteolysis and cumulus expansion. 748 19

The role of vascular cyclooxygenase pathway on tissue-type plasminogen activator (t-PA) release after venous occlusion was studied in anesthetized rats. After the inferior vena cava was clamped for 30 min, fibrinolytic activity increased from 143.7 +/- 14.5 to 209.5 +/- 10.3 mm2 (mean +/- SE, P < 0.002). This increase was prevented by aspirin at high (100 mg/kg i.v.) but not at low doses (1 mg/kg i.v.). Dazoxiben (10 mg/kg i.v.), an inhibitor of thromboxane synthase, was ineffective on the fibrinolytic response. Both the basal levels of 6-ketoprostaglandin F1 alpha and its increase after venous occlusion were suppressed by 100 mg/kg aspirin administration (from 0.64 +/- 0.2 to 0.05 +/- 0.002 ng/ml before occlusion, P < 0.001; and from 1.08 +/- 0.2 to 0.06 +/- 0.002 ng/kg after occlusion, P < 0.001), whereas they were both unaffected by aspirin at low doses (from 0.53 +/- 0.06 before to 1.20 +/- 0.08 ng/ml after stasis). Moreover, iloprost, a stable analogue of prostacyclin, reversed the aspirin inhibitory effects on fibrinolytic activity by restoring t-PA vascular release after venous stasis. Our results provide experimental evidence that an intact cyclooxygenase pathway in vascular wall is required for the fibrinolytic activity increase after venous occlusion in rats.
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PMID:Prostacyclin is required for t-PA release after venous occlusion. 751 45

The aim of the present study was to determine the role of transforming factor alpha (TGF alpha) and beta (TGF beta) in the regulation of prostaglandin (PG) secretion, and the relationships between PG and plasminogen activator (PA) activity in hen granulosa cells during ovarian follicular development. Cells from the first (F1), third (F3), and fifth and sixth (F5-6) largest preovulatory follicles were cultured for up to 21 h in the presence of TGF alpha (0.1-10 ng/ml) and/or TGF beta (4-20 ng/ml) or TGF alpha together with a cyclooxygenase inhibitor, indomethacin (0.05-0.5 microM). The release of PG into the incubation medium was determined by RIA. Cell-associated (PAc) and secreted (PAs) PA activities were measured by a fibrinolysis assay and characterized by zymography. Basal PGF secretion from F1, F3, and F5-6 cells was 2.2 +/- 0.3, 2.2 +/- 0.5, and 1.1 +/- 0.3 ng/micrograms DNA, respectively, and was higher than that of PGE. Basal total PA (PAc+PAs) activity from F1, F3, and F5-6 cells was 41 +/- 13,261 +/- 68, and 958 +/- 268 x 10(3) cpm/micrograms DNA, respectively. TGF alpha stimulated PG secretion and PA activity in a dose-dependent manner. The TGF alpha-induced PA activity was predominantly associated with a molecular mass of 30-35 kDa, corresponding to that of urokinase PA. The stimulation of PG secretion by TGF alpha was maximal in F3 and F1 granulosa cells whereas PA activity in the presence of TGF alpha was highest in cells from F5-6 follicles.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Avian granulosa cell prostaglandin secretion is regulated by transforming growth factor alpha and beta and does not control plasminogen activator activity during follicular development. 781 60

We evaluated the effects of fatty-acid anilides (FAA) on prostacyclin (PGI2) synthesis and on the fibrinolytic properties of human umbilical vein endothelial cells. Preincubation of endothelial cells with oleic- and linoleic-anilides (OAA and LAA, respectively) resulted in a time- and concentration-dependent inhibition of ionophore A23187- and thrombin-induced PGI2 synthesis. However, no significant effects of FAA on arachidonic acid-induced PGI2 synthesis were found, except with 1000 microM LAA which inhibited cyclooxygenase activity after 24 h. In general terms, OAA showed similar inhibitory effects on PGI2 production as did LAA, but with a shifted time course, since the production of PGI2 at 24 h for OAA was similar to that observed for LAA at 2 h. The release of labeled arachidonic acid from cell membranes was significantly reduced (75-85%), after 24 h, with both FAA. The effect of 100 microM LAA on thrombin-induced PGI2 production was rapid (within 15 min) and irreversible after 60 min. The recovery of PGI2 synthesis after LAA treatment was blocked by cycloheximide, suggesting a decrease of phospholipase(s) activity or cessation of enzyme synthesis. Moreover, this reduced PGI2 synthesis was not associated with [3H]adenine release. Our data indicate that FAA induce a significant impairment of stimulated PGI2 synthesis and arachidonic acid release in endothelial cells, acting primarily as inhibitors of phospholipase(s) rather than of cyclooxygenase. Finally, both LAA and OAA induce an anti-fibrinolytic activity in these cells where major changes are observed in the plasminogen activator inhibitor and the urine-type plasminogen activator.
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PMID:Effects of linoleic and oleic acid anilides on prostacyclin synthesis and fibrinolytic profile of human endothelial cells in culture: relevance to the toxic oil syndrome. 821 24

Over the last few years methods have been developed to assess appearance of thrombin during blood clotting in a clinical setting. This can be achieved either by measurement of the specific thrombin markers or by analysis of the thrombin generation kinetics. Thrombin markers rise following coronary occlusion and, surprisingly, their plasma levels become further increased during and after thrombolytic treatment with streptokinase or tissue-plasminogen activator. In myocardial infarction enhanced thrombin generation extends over the weeks, well beyond the acute phase of the disease. It indicates increased risk to a patient and might call for more anticoagulation or angioplasty. The benefit of aspirin as conjunctive treatment for thrombolysis has been clearly demonstrated. The well-founded concept is that aspirin exerts its anti-thrombotic action through inhibition of platelet cyclooxygenase. Recent evidence indicates that antithrombotic effects of aspirin might be explained, partly at least, by its inhibition of thrombin formation. Indeed, in both healthy subjects and survivors of myocardial infarction, aspirin, either at a single dose of 500 mg or at a dose of 300 mg per day administered over two weeks, effectively inhibits thrombinogenesis. Such response to aspirin is blunted in hypercholesterolemia. Subjects with high serum cholesterol levels might profit less than others from the anti-thrombotic action of aspirin.
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PMID:Thrombin generation in myocardial infarction and hypercholesterolemia: effects of aspirin. 857 30

We investigated changes in vascular reactivity to endothelin (ET) and local release of ET-like immunoreactivity (ET-LI) induced by myocardial ischemia and reperfusion in a pig model of coronary thrombosis and thrombolysis and studied the possible mechanisms producing the changed vascular reactivity to ET-1. We induced coronary thrombosis by inserting a copper coil into the left anterior descending coronary artery (LAD) and achieved thrombolysis with tissue plasminogen activator (t-PA). Vascular reactivity to ET-1 in the nonischemic and ischemic/reperfused LAD diagonal branches was evaluated in vitro. ET-LI was analyzed in plasma from the great cardiac vein and aorta for estimation of local release. The vasoconstrictor response to ET-1 was enhanced twofold (p < 0.01) in the ischemic/reperfused arteries as compared with the nonischemic arteries. The vasoconstriction induced by the ETB receptor agonist [Ala 1,3,11,15] ET-1 or serotonin was not significantly affected by ischemia/reperfusion. The ETA receptor antagonist BQ-123 reversed the ET-1-induced vascular contraction to a similar degree in ischemic/reperfused and control arteries. The ET-1-induced vasoconstriction of control arteries was not affected by inhibition of nitric oxide (NO) synthase with NG-nitro-L-arginine (L-NNA) or cyclooxygenase with indomethacin. During reperfusion, the myocardial venoarterial plasma concentration difference of ET-LI and blood flow increased, resulting in an increased overflow of ET-LI. Our results demonstrate that coronary thrombosis and thrombolysis evokes enhanced local release of ET-LI during the reperfusion period and increases the vasoconstrictor effects of ET-1 through a mechanism related to ETA receptor activation but unrelated to altered endothelial function. These changes may play a role in the development of ischemic/reperfusion injury and no-reflow phenomenon.
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PMID:Myocardial release of endothelin (ET) and enhanced ET(A) receptor-mediated coronary vasoconstriction after coronary thrombosis and thrombolysis in pigs. 863 92

Platelets play a vital role in mediating the activity of plasma fibrinolytic system. They have both the potential to inhibit as well as to activate fibrinolysis. Just as platelet can affect thrombolysis, thrombolytic agents can have reciprocal effects on platelet function. Accumulating evidence indicates that thrombolysis induced both by streptokinase and t-PA results in rapid activation of platelets, the phenomenon being possibly responsible for reocclusion of arteries after successful thrombolysis. However, caution is required in comparing the results of the various studies because of differences in the thrombotic models employed, with the major variables being the mechanism of thrombus formation (in vivo or in vitro), the platelet concentrations and the doses of investigated agent. Various studies indicate that adjunctive therapy with anti-platelet agents, such as inhibitors of cyclooxygenase, inhibitors of thromboxane A2-synthase and activators of platelet cyclic-AMP or -GMP may lower the dose of the thrombolytic agent required to attain reperfusion.
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PMID:Platelets in fibrinolytic system. 877 Jul 85

Serotonin stimulates phospholipase A(2)(PLA(2)) leading to the production of prostaglandin products, several of which are vasoconstrictors. We hypothesised that the elevated vascular responsiveness to serotonin in deoxycorticosterone acetate (DOCA)-hypertensive rats is due in part to augmented production of vasoconstrictor cyclooxygenase products (e.g. PGF(2)alpha). Denuded helical strips of femoral arteries from DOCA-salt hypertensive rats (SBP 183 +/- 7 mmHg) and normotensive control rats (SBP 115 +/- 2) were used in all experiments. EC(50) values for several agonists were significantly reduced in DOCA arteries compared with controls (in mu mol/L, control vs. DOCA): PGF(2)alpha (0.99 vs. 0.23), PGE(2) (0.72 vs. 0.22), arachidonate (1.52 vs. 0.73), serotonin (0.19 vs. 0.07), noradrenaline (0.029 vs. 0.013), KCl (40.1 vs. 27.0 mmol/L) and AlF(4) (2.3 vs. 1.4 mmol/L). Treatment with indomethacin (14 mu mol/L) inhibited the responses to serotonin in DOCA arteries (EC(50) values 0.07 untreated vs. 0.70) and eliminated the responses to arachidonate but did not affect KCl or AlF(4-)contractions. Cyclooxygenase inhibitors shifted concentration response curves to serotonin in sham and DOCA tissues equally. Thus increased sensitivity to serotonin in DOCA arteries persisted following cyclooxygenase blockade. Therefore, although arachidonate products contribute to the serotonergic contraction in femoral arteries, the augmented response in arteries from DOCA hypertensive rats is not due to increased production of or sensitivity to cyclooxygenase products. Furthermore,arachidonate metabolites do not contribute to the contraction induced by either AlF(4-)or KCl in this preparation.
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PMID:Arachidonate metabolites and serotonin contraction of femoral arteries from DOCA-salt hypertensive rats. 886 Jan

In vivo a powerful triad of endothelial secretogogues regulates thrombo-resistance and vascular tone. In physio-pathological circumstances stimulation of endothelial receptors (purinergic, muscarinic, kinin) releases prostacyclin (PGI2), nitric oxide (NO) and tissue plasminogen activator (t-PA) in a coupled manner. Alliance between them occurs at level of protection against deposition of thrombi over the vascular wall. Activation of fibrinolysis by t-PA through generation of plasmin is complemented with multifactorial desactivation of platelets by PGI2 and a selective inhibition of release of plasminogen activator inhibitor-1 (PAI-1) from platelets by NO. This concerted action of the triad leads to increase in anti-thrombotic and thrombolytic potentials. Administrated separately t-PA (or streptokinase) and PGI2 (or iloprost) produce unwanted effects such as "paradoxic thrombogenesis" or "rebound activation of platelets", respectively. It is because they are missing a natural ally. On the other hand, endothelial regulation of vascular tone depends on NO, exclusively. Only exogenous PGI2 is hypotensive, and even then it does not synergize with NO. In vitro all types of interactions between PGI2 and NO occur. For instance, synergism--in platelets, addition--in vascular smooth muscle and antagonism--in macrophages. Activity of arachidonate cyclooxygenase is claimed to be either stimulated or inhibited by NO. A transfer of conclusions from in vitro data to living systems must be very cautious.
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PMID:Endothelial nitric oxide, prostacyclin (PGI2) and tissue plasminogen activator (t-PA): alliance or neutrality? 886 42

Sotalol is a beta-adrenoreceptor blocking drug, the clinical efficacy of which has been linked up to its negative chrono- and inotropic effects and its hypotensive action. In addition, beta-adrenolytic drugs are known to inhibit platelet aggregation in vitro possibly through lowering of calcium ions level. Here, we report that in rats sotalol at a dose of 10-20 mg/kg i.v., apart from hypotension, evokes instantaneous thrombolytic effect. This is associated with an increase in plasma level of tissue plasminogen activator (t-PA). In vitro, sotalol at a concentration of 1-100 microM inhibits thrombogenesis on surface of rabbit aorta endothelium superfused with blood. Sotalol also has a weak anti-aggregatory activity (IC50 approximately 500-1000 microM) in human platelet rich plasma (PRP). Since the thrombolytic and fibrinolytic but not hypotensive effects of sotalol were inhibited by cyclooxygenase inhibitor, indomethacin, while its hypotensive but not thrombolytic potency was dimished by an inhibitor of nitric oxide synthase, NG-nitro-L-arginine (L-NNA), we have linked up the sotalol-induced effects in vivo with the release of prostacyclin and nitric oxide. Our data point out to a possibility that prostacyclin and nitric oxide concomitantly released from endothelium and/or from other blood cells after administration of sotalol, may play different roles: prostacyclin may be responsible for fibrinolytic, thrombolytic and antithrombotic properties, while nitric oxide may take part in the mechanism of sotalol-induced hypotension.
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PMID:Thrombolytic activity of beta-adrenolytic drug, sotalol. 959 10


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