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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Low (LDL) and high (HDL) density lipoproteins stimulate prostacyclin (PGI2) synthesis in cultured rabbit and human aortic smooth muscle cells. In this respect, the efficacy of HDL exceeded that of LDL, HDL3 being the most effective. HDL3 obtained from hypoalphacholesterolemic patients' serum had a lesser stimulative effect on PGI2 synthesis as compared with HDL3 of normolipidemic subjects. Partially purified apoprotein A-1 stimulates the metabolism of 14C-arachidonic acid accompanied with enhanced formation of prostaglandins, especially 6-keto-PGII alpha. Within a 24 h incubation in the fetal calf serum-free medium, prostaglandins I2 and E1 (1 x 10(-7) M) reduce the intracellular cholesterol level in human aortic smooth muscle cells by 30%. Total HDL fraction as well as HDL3 and HDL2b applied in combination with prostaglandins have a synergistic effect resulting in a 50% fall in intracellular cholesterol. Hypothetically, the uptake of cholesterol by HDL may include the following stages: (1) HDL interacts with the cell and activates the intracellular PGI2 synthesis probably via apo A-1 modulatory action on arachidonic acid metabolism; (2) newly synthesized PGI2 activates cholesteryl ester hydrolase leading to the formation of free cholesterol; (3) HDL takes up free cholesterol.
J Mol Cell Cardiol 1989 May
PMID:Prostacyclin-mediated effect of high density lipoproteins as cellular cholesterol acceptors on aortic smooth muscle cells. 267 51

We have previously observed a long-lasting antiischemic and antiarrhythmic effect induced by prostacyclin (PgI2) or its stable analogue, 7-oxo-PgI2-ephedrine salt in dogs subject to local myocardial ischemia. This protection appeared when the vasodilating and platelet aggregation inhibiting effect of PgI2 or its analogue was over and persisted even 72 h after treatment. We have also found that short incubation with 7-oxo-PgI2 may induce a long-lasting prolongation of the action potential duration and of the effective refractory period in the isolated rabbit papillary muscle preparation without affecting the membrane potential or the rate of rise of the action potential. Our present experiments have shown a 7-oxo-PgI2 induced, dose-dependent prolongation of the ventricular functional refractory period in conscious rabbits and anesthetized dogs, as well as an increase of the QT interval in the ECG in both species and also in conscious guinea-pigs. In all three species 50 micrograms/kg i.m. dose proved to be optimal, evoking maximal effect 48 h after treatment. In conscious rabbits this pre-treatment prevented the train of non-stimulated extra beats induced by premature stimuli. Furthermore it also prevented widening of the QRS complex appearing in non-treated controls after programmed stimulation. Pre-treatment significantly increased electrical fibrillo-flutter thresholds in the auricles and ventricles of anesthetized cats. These electrophysiological changes seem to be closely related to the 7-oxo-PgI2 induced, late appearing and long-lasting protection from ischemic and reperfusion arrhythmias.
J Mol Cell Cardiol 1989 Jun
PMID:7-oxo-PgI2 induced late appearing and long-lasting electrophysiological changes in the heart in situ of the rabbit, guinea-pig, dog and cat. 267 53

The precise role of eicosanoids in the development of myocardial injury during ischemia and reperfusion is still a matter of debate. Enhanced local production of these bioactive compounds appears to be a common response to tissue injury. Most likely, the cardiac tissue has the capacity to generate prostaglandins, thromboxanes as well as leukotrienes. Prostacyclin (PGI2) is the major eicosanoid produced by the jeopardized myocardium. In addition, at sites of tissue injury activation of platelets and infiltrating leukocytes results in the formation of considerable amounts of thromboxanes and leukotrienes. The production of eicosanoids requires prior release of arachidonic acid (AA) from phospholipids. Both ischemia and reperfusion are associated with a rise in the tissue level of AA. The absence of a proportional relationship between the tissue level of AA and the amounts of PGI2 produced suggests that the sites of AA accumulation and PGI2 formation are different. It is conceivable that AA accumulation is mainly confined to myocytes, whereas the capacity to synthesize PGI2 mainly resides in vascular cells. Both beneficial and detrimental effects of eicosanoids on cardiac tissue have been described. Prostaglandins act as vasodilators. Besides, some of the prostaglandins, especially PGI2, are thought to possess cyto-protective properties. Thromboxanes and leukotrienes may impede blood supply by increasing smooth muscle tone. Besides, leukotrienes augment vascular permeability. Experimental studies, designed to evaluate the effect of pharmacological agents, like PGI2-analogues and lipoxygenase and cyclo-oxygenase inhibitors, indicate that eicosanoids influence the outcome of myocardial injury.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem
PMID:Significance of myocardial eicosanoid production. 267 62

The protection of angiotensin converting enzyme (ACE) inhibitors, captopril and ramiprilat, against free radical-mediated myocardial injury were studied in isolated working rat hearts. Free radicals were generated by electrolysis of Krebs-Henseleit solution with 10 mA direct current for 1 min. Both captopril (360 mumol/l) and ramiprilat (12.5 mumol/l) significantly reduced the decrease of left ventricle dP/dt'max, coronary flow (CF), myocardial superoxide dismutase (SOD) and creatine kinase (CK) activities and the elevation of S-T segment of epicardial ECG as well as the rise of myocardial malondialdehyde (MDA) content caused by electrolysed perfusate. Captopril afforded a dose-dependent protection on cardiac functions with various concentrations of 45, 90, 180 and 360 mumol/l. Iloprost (30 nmol/l), a stable mimetic of prostacyclin, could also alleviate free radical-mediated myocardial injuries. All the beneficial effects of ramiprilat (12.5 mumol/l) were abolished by the administration of indomethacin (5 mumol). In contrast, captopril (90 mumol/l) still exhibited significant protective effects after indomethacin (9 mumol) was administered, though these protective effects were insignificantly weakened. In order to assess the role of sulfhydryl (-SH) group in the effects of captopril, a SH-containing drug S8 and a disulfide DG4, both are deficient in ACE inhibitory properties in vitro, were examined. Data showed that S8 (180 mumol/l) provided a significant protection while DG4 showed no protective effect. It is concluded that ACE inhibitors can protect against free radical-induced myocardial damage. Ramiprilat, a non-SH-containing ACE inhibitor, inhibits free radical-induced damages mainly by stimulation of prostacyclin synthesis and/or release. In addition to this effect, captopril, a SH-containing ACE inhibitor, may exert additional anti-free radical effects by a mechanism which is probably related to the sulfhydryl group.
J Mol Cell Cardiol 1989 Dec
PMID:Captopril and ramiprilat protect against free radical injury in isolated working rat hearts. 269 63

The effects of CGS 13080, a thromboxane (TXA2) synthase inhibitor, on airway responses to arachidonic acid (AA) were investigated in the anesthetized cat. Feline and human lung microsomal fraction exhibited prostaglandin I2 (PGI2, prostacyclin), and TXA2 synthase activities, and human platelet microsomal fractions exhibited TXA2 synthase activity. Cat and human lung microsomal fractions, but not human platelets, exhibited the presence of GSH-dependent PGE2 isomerase activity. CGS 13080 inhibited TXA2 synthase activity in all three microsomal fractions in a concentration-dependent manner. The increases in transpulmonary pressure and lung resistance and decreases in dynamic compliance in response to AA were decreased significantly by CGS 13080. These data suggest that the bronchoconstrictor actions of AA are mediated in large part by the formation of TXA2. The data further indicate that cyclooxygenase products other than TXA2 are involved in the bronchoconstrictor response to AA since meclofenamate had greater inhibitory activity than did CGS 13080. Moreover, the effects of CGS 13080 were due to inhibition of TXA2 synthase rather than an effect on TXA2 receptors, since airway responses to the TXA2 mimic, U46619, were not altered. The present data show that CGS 13080 inhibits TXA2 synthase activity without altering cyclooxygenase, PGI2 synthase, or GSH-dependent PGE2 isomerase activities. The data further indicate that in vivo administration of CGS 13080 may selectively increase PGI2 synthase activity.
Mol Cell Biochem 1989 Jan 23
PMID:Inhibition of pulmonary thromboxane A2 synthase activity and airway responses by CGS 13080. 272 78

We examined the mechanisms by which the phospholipid-sensitive, calcium-dependent protein kinase (protein kinase C) regulates prostacyclin synthesis by ovarian cells. In monolayer cultures of swine granulosa cells, specific phorbol esters significantly augmented production of the stable immunoreactive metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha by 3- to 8-fold. These stimulatory actions were dose (0.03-30 ng/ml) and time (24-96 h) dependent, could be reproduced by non-diterpene activators of protein kinase C, and were corroborated by high performance liquid chromatography and mass spectrometry. The rank order of potency of phorbol esters was 12-O-tetradecanoylphorbol 13-acetate (TPA) greater than phorbol 12,13-dibenzoate greater than phorbol 12,13-dibutyrate greater than pure phorbol base. TPA enhanced de novo synthesis of prostacyclin, and synergized with the divalent cation ionophore, A23187. Although prostacyclin synthetase activity was not induced, microsomal cyclooxygenase activity was significantly increased by phorbol treatment. Moreover, TPA doubled the intracellular accumulation of free arachidonic acid. An inhibitor of phospholipase A2 (quinacrine 100 microM) impeded, whereas melittin (0.01 microM), an activator of cellular phospholipase A2, and purified bacterial phospholipase A2 (5 and 50 mU/ml) both augmented prostacyclin production. RH 59022 (30 microM), an inhibitor of diacylglyceride lipase, also suppressed prostacyclin synthesis. We conclude that the protein kinase C effector pathway is functionally coupled to de novo prostacyclin production in the swine granulosa cell. Increased eicosanoid synthesis can be accounted for by enhanced phospholipase A2 and diacylglyceride lipase-mediated availability of arachidonic acid substrate and an activated cyclooxygenase enzyme without a change in prostacyclin synthetase activity.
Mol Cell Endocrinol 1989 May
PMID:Mechanism(s) by which activation of protein kinase C is coupled to prostacyclin synthesis in granulosa cells. 275 27

The protective effect of angiotensin-converting enzyme inhibitors (ACEI) on myocardial ischemia and reperfusion damage was estimated in rat hearts, both in vivo and in vitro. Enalapril 2.5 mg/kg ip pretreatment at 24 and 5 h before coronary occlusion, significantly blunted the rise of CPK (445 +/- 151 vs 649 +/- 244 mu/ml, P less than 0.05) and improved electrocardiogram (ECG) 8 h after coronary occlusion. In global ischemia and reperfusion ex vivo, enalapril improved contractility (0.9 +/- 0.2 vs 0.3 +/- 0.3 g, P less than 0.05) and coronary flow (15.6 +/- 3.3 vs 11.9 +/- 3.1 ml/min/g, P less than 0.05), shortened significantly the duration of reperfusion arrhythmia (3.1 +/- 2.7 vs 9.7 +/- 8.1 min, P less than 0.05). In Langendorffs heart, captopril remarkably preserved force of contraction (2.1 +/- 0.4 vs 1.4 +/- 0.4 g, P less than 0.01) and coronary flow (2.7 +/- 0.5 vs 3.6 +/- 0.9 ml/min/g, P less than 0.05) in segmental infarction deteriorated by angiotensin I. Captopril 10(-5) M infusion reduced the release of CPK (435 +/- 112 vs 640 +/- 123 mu/min coronary flow, P less than 0.05). This action was almost completely abolished by pretreating and infusing with indomethacin. As a positive control, prostacyclin 5 X 10(-7) M infusion further reduced the release of CPK to 330 +/- 77 mu/min. It is concluded that angiotensin-converting enzyme inhibitor can protect both myocardial ischemia and reperfusion damage in rat hearts. The mechanism of protection was ascribed to reduced production of angiotensin II by ACE inhibition and increased prostacyclin release in the myocardium.
J Mol Cell Cardiol 1987 Sep
PMID:Protective effects of captopril and enalapril on myocardial ischemia and reperfusion damage of rat. 282 45

To study the roles played by cardiac valvular endothelium in normal and pathologic conditions, we have established and characterized a system of bovine valvular endothelial cells (VEC) in culture. Viable VEC from calf atrioventricular valves were obtained by a non-enzymatic procedure using 3 mM ethylenediamine-tetraacetic acid (EDTA) as dissociating agent. The cells grown in Dulbecco's modified Eagle's medium supplemented with non-essential amino acids, vitamins and 20% fetal calf serum, developed as monolayers of closely apposed polygonal cells which were subcultured for up to seven passages. VEC maintained in culture the general ultrastructure displayed in vivo, expressed von Willebrand factor, presented angiotensin converting enzyme activity and synthesized a rich extracellular matrix. VEC preserved the cell surface anionic sites (detected with cationized ferritin, pI 8.4) and cationic sites (visualized with haemeundecapeptide pI 4.85), and took up, especially by adsorptive endocytosis, albumin-gold conjugate. The cells were coupled by functional communicating (gap) junctions, as demonstrated by microinjection of 6-carboxyfluorescein. VEC in culture produced fibronectin, prostacyclin, hyaluronic acid and heparin-like glycosaminoglycans (identified by electrophoresis, enzyme digestion, and deaminative cleavage of molecules). These properties render cultured VEC a suitable model for investigating their functions and involvement in normal and pathologic heart valves.
J Mol Cell Cardiol 1988 Feb
PMID:Calf cardiac valvular endothelial cells in culture: production of glycosaminoglycans, prostacyclin and fibronectin. 284 May 11

Platelet activating factor (PAF) stimulated production of prostaglandin (PG) I2, PGE2, and PGF2 alpha by rat liver cells (the C-9 cell line); as little as 0.2 nM PAF was effective. Enantio-PAF was 1000-fold less effective. Lyso-PAF, at levels ranging from 0.1 to 1.0 microM, did not stimulate PGI2 production. The synthesis of PGI2 was essentially complete in 10 min. The stimulation by PAF of PGI2 production was inhibited by the PAF antagonists L-659,989, kadsurenone, L-652,731, and BN 52021; the values for 50% inhibition (IC50) were 0.02, 0.19, 0.21, and 0.73 microM, respectively. The antagonists L-659,989 and BN 52021 had no effect on the levels of 6-keto-PGF1 alpha stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA), palytoxin, melittin, the Ca2+ ionophore-A-23187, colchicine, transforming growth factor alpha, or exogenous arachidonic acid. The effect of PAF on arachidonic acid metabolism was inhibited by prior exposure of the cells to PAF. Prior treatment of the rat liver cells at 37 degrees with the TPA-type tumor promoters TPA, teleocidin, and aplysiatoxin, as well as with the second stage tumor promoter mezerein, all of which activate the Ca2+/phospholipid-dependent protein kinase (protein kinase C), resulted not only in homologous desensitization to the TPA-type tumor promoters and mezerein, but also in heterologous desensitization to PAF. Stimulation of PGI2 production by palytoxin, the Ca2+ ionophore A-23187, or exogenous arachidonic acid was not inhibited by such prior treatments with the TPA-type tumor promoters. Prior treatment of the cells at 37 degrees for 30 min with the non-TPA-type tumor promoters okadaic acid or palytoxin, both of which do not activate protein kinase C, did not result in heterologous desensitization to PAF.
Mol Pharmacol 1988 Dec
PMID:Platelet-activating factor stimulates arachidonic acid metabolism in rat liver cells (C-9 cell line) by a receptor-mediated mechanism. 284 46

The effects of agents that cause vasodilatation and hypotension, such as endogenously produced bradykinin (BK) or the drug nitroprusside (NP), appear to result from effects on cyclic nucleotides (cGMP, cAMP) and arachidonate metabolism. Cultured human fibroblasts, which possess B2 BK receptors and respond to NP with an increase in cGMP, were used to study the interaction of these agents at the molecular level. Addition of BK or NP to cultured human fibroblasts caused a rapid increase in cGMP. The effect of NP was usually maximal within 30 sec, after which cGMP content declined. The increase in cGMP produced by BK reached a maximum at approximately 1 min and then fell; the rise with NP was more than 10 times that with BK. At 30 sec, cGMP content with NP plus BK was less than with NP alone. At later times, however, effects of BK and NP were slightly more than additive and maximal cGMP levels were reached at 90 sec. BK increased prostaglandin production by the fibroblasts; it is believed that the kinin-induced elevation in cAMP content is secondary to increased prostaglandin formation. NP caused a small, early increase in cAMP without significant effect on prostaglandin I2 (PGI2); after 2.5 min, effects on PGI2 and cAMP were greater with BK and NP than with BK alone. To study further the roles of arachidonate metabolites in the fibroblast response to BK and NP, the cyclooxygenase inhibitor, indomethacin, and the combined lipoxygenase and cyclooxygenase inhibitor, 5,8,11,14-eicosatetraynoic acid (ETYA), were added to fibroblasts prior to BK or NP. Increases in cAMP or PGI2 with BK or BK plus NP were blocked by indomethacin or ETYA. These effects of BK or BK plus NP on cAMP thus appear to be mediated through cyclooxygenase products of arachidonate metabolism. Indomethacin and ETYA did not affect cGMP in the presence of BK plus NP but enhanced NP-stimulated cGMP accumulation by 40-50%; effects of NP on cGMP may be independent of or perhaps inhibited by cyclooxygenase derivatives. Cellular responses to BK plus NP differed quantitatively and temporally from the sum of effects of BK and NP alone. Through interactions of this type, in vivo responses to drugs like NP may be influenced by levels of BK or similar endogenous mediators.
Mol Pharmacol 1986 Sep
PMID:Effects of nitroprusside on the bradykinin responsiveness of human fibroblasts. 301 83


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