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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prostaglandins (PG) are highly unsaturated, cyclic fatty acids with 20 carbon atoms which are biosynthesized from dihomo-gamma-linolenic, arachidonic and eicosapentaenoic acids. These fatty acids are either ingested or are biosynthesized from linoleic and linolenic acids, respectively. The PG-precursor fatty acids are liberated from membrane phospholipids by phospholipase A and are converted to prostaglandins by the multienzyme complex PG-synthetase. The activity of the PG-system is influenced by extracellular hormonal, neural and mechanical stimuli and by intracellular factors such as ion-concentration and activity of the enzymes adenyl- and guanylcyclase. Prostaglandins are tissue hormones or autacoids which act on their receptors near their site of synthesis and degradation. The prostaglandin family constitutes a group of more than 10 natural occurring compounds showing a variety of biological actions. In arteries and veins the different PG:s have vasodilating as well as vasoconstricting effects. In addition, they are involved in the regulation of vascular smooth muscle proliferation. Within the kidney PG:s have vascular and tubular actions. They antagonize the effect of ADH, mediate renin secretion and are involved in the control of electrolyte balance. In the regulation of platelet aggregation and platelet adhesion PG:s have opposite functions: Prostacyclin which is synthesized in the vascular wall antagonizes the aggregating action of Thromboxane A2 which is formed in the platelets. A defect or an imbalance in the production of PG:s in the vascular wall, in platelets or in the kidney is assumed to play a pathogenetic role in a variety of cardiovascular and renal diseases such as in hypertension, atherosclerosis, persistent ductus arteriosus and Bartter's syndrome.
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PMID:[Prostaglandins in cardiovascular and renal function. Biochemical, physiological and clinical findings (author's transl)]. 10 97

Thromboxane A2 (TxA2) is the main arachidonic acid metabolite in human platelets and exhibits two major activities; stimulation of platelet function, including secretion of platelet-derived storage products, e.g., 5-HT, PDGF, and vasoconstriction. Platelet hyperreactivity is typical for advanced stages of atherosclerosis and is paralleled by elevated circulating thromboxane levels. This is the target for TX-antagonistic compounds. Three classes of selective compounds are available: inhibitors of thromboxane synthase, antagonists of thromboxane receptors, and mixed-type agents. Positive experimental data with all of these compounds are available. However, clinical experience is limited and, in general, not convincing. This review discusses possible reasons for that and suggests that, in particular, the use of combined-type agents as antithrombotics may be superior to acetyl-salicylic acid in several forms of ischemic cardiovascular diseases.
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PMID:[Thromboxane A2 and prevention of cardiovascular diseases]. 129 Feb 97

Thromboxane A2 (TXA2) biosynthesis was studied in healthy subjects, patients with chronic cerebral infarction, patients under chronic aspirin treatment and patients with atrial fibrillation. Urinary 11-dehydro-TXB2, as a major metabolite of TXA2, was measured by radioimmunoassay. The extent of carotid atherosclerosis was determined by B-mode ultrasonography. The mean +/- SD urinary excretion in patients with cerebral infarction and distinct carotid-atherosclerotic lesions (1,725 +/- 239 ng/g creatinine, n = 6) was significantly higher (p less than 0.01) than in healthy subjects (911 +/- 239 ng/g creatinine, n = 44) and patients with cerebral infarction who had no distinct carotid lesion (1,050 +/- 191 ng/g creatinine, n = 6). The urinary excretion of healthy subjects was higher (p less than 0.01) in smokers (1,063 +/- 244 ng/g creatinine, n = 17) than in non-smokers (815 +/- 183 ng/g creatinine, n = 27). Aspirin largely suppressed 11-dehydro-TXB2 excretion (266 +/- 114 ng/g creatinine, n = 7). Three of 5 patients with atrial fibrillation showed very high values. Our results indicated that platelet activation occurs in the atherosclerotic lesions, and that urinary 11-dehydro-TXB2 is the appropriate analytic target for detecting platelet activation.
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PMID:Urinary 11-dehydro-thromboxane B2: a quantitative index of platelet activation in cerebral infarction. 139 73

In 35 pigs atherosclerosis was induced by balloon abrasion and a diet containing 2% (w/w) cholesterol and 7% (w/w) lard fat. After 4 months of induction nine animals were killed (I) for analysis of the extent of atherosclerosis, while the diet of the other 26 pigs was changed to a low cholesterol diet containing either 9% (w/w) lard fat (L), 9% (w/w) fish oil (F) or 4.5% (w/w) lard fat and 4.5% (w/w) fish oil (LF). This diet was continued for 3 months to induce regression of atherosclerosis. The cholesterol-rich diet increased plasma total cholesterol, but did not affect plasma triglycerides. Low-cholesterol feeding decreased plasma total cholesterol in all three groups, but triglycerides only in LF and F. Lipid infiltration of the aortic wall was similar in I, L, LF and F. In the denudated coronary arteries of I mean luminal encroachment was 11 +/- 2%. This was similar in L (13 +/- 4%) but significantly lower (P less than 0.05) in LF (6 +/- 2%) and in F (3 +/- 1%). In the non-abraded coronary arteries of I mean luminal encroachment was 1.3 +/- 0.3%. For F and LF similar values were found, but in L there was an increase to 11 +/- 3% during low-cholesterol feeding. ADP-induced platelet aggregation was lower in LF and F than in L. Thromboxane A2 production was only reduced in F, while the production of the weak thromboxane A3 agonist was larger in F than in LF. It is concluded that fish oil retards the progression of and causes regression of coronary atherosclerosis.
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PMID:Mackerel oil and atherosclerosis in pigs. 280 83

In monkeys with early and advanced atherosclerosis, we examined responses to the three major vasoactive agonists that are released when platelets aggregate. Measurements were obtained in normal cynomolgus monkeys and in monkeys fed an atherogenic diet for 4 +/- 1, 9 +/- 1, and 19 +/- 1 months (mean +/- SEM). Morphometry of femoral and iliac arteries indicated that 4 months of atherogenic diet produced only slight intimal thickening, 9 months produced early lesions, and 19 months produced approximately 5-10 fold greater intimal proliferation than did 9 months of atherogenic diet. Serotonin and adenosine 5'-diphosphate (ADP), which are endothelium-dependent agonists, and adenosine and phenylephrine, which are endothelium-independent agonists, were injected intra-arterially into the perfused hind limb. Thromboxane A2 analogue U46619 also was studied. Vasoconstrictor responses to serotonin were potentiated, and vasodilator responses to ADP were impaired by early and advanced atherosclerosis. In contrast, vasoconstrictor responses to phenylephrine and vasodilator responses to adenosine were similar in all groups. Vasoconstrictor responses to U46619 were potentiated by advanced atherosclerosis. Thus, vascular responses to serotonin, ADP, and thromboxane A2 are altered by atherosclerosis in a direction that would favor vasoconstriction when platelets aggregate. Furthermore, because responses to endothelium-dependent agonists are altered, these data suggest that endothelium is dysfunctional in early atherosclerosis. These findings may explain, in part, the propensity for exaggerated vasoconstriction even in arteries with minimal atherosclerotic lesions.
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PMID:Effect of early and advanced atherosclerosis on vascular responses to serotonin, thromboxane A2, and ADP. 291 93

RS-93427 is a potent, orally active prostacyclin-mimetic that is very rapidly absorbed but with generally long-lived actions in most species. It has antithrombotic, thrombolytic, and antivasospastic potential. Alone among several tested PGI-mimetics, it inhibits release of platelet mitogens more potently than its ability to inhibit aggregation. It also inhibits mitogen release from macrophages and vascular endothelial cells. RS-93427 is also potent at inhibiting macrophage accumulation of cholesteryl esters. These data suggest a broad spectrum of potential therapeutic utility for RS-93427 via the oral route. It might be useful both in acute manifestations of vascular occlusive disease involving thrombosis and vasospasm, in addition to the more chronic conditions involving intimal hyperplasia (as in arteriovenous grafts) and possibly frank atherosclerosis. Much work remains to be done, including examination of RS-93427 in chronic studies with various dosage forms, particularly in the study of atherosclerosis.
Adv Prostaglandin Thromboxane Leukot Res 1987
PMID:Orally active prostacyclin-mimetic RS-93427: therapeutic potential in vascular occlusive disease associated with atherosclerosis. 295 59

Thromboxane and prostacyclin metabolite determinations (radioimmunoassay) were performed in obliterative atherosclerosis and in diabetes mellitus with microangiopathy. The shift of these metabolites to the thromboxane side could have been documented in both diseases. This phenomenon calls attention to an increased platelet activation and endothelial cell damage. In a third group patients received aspirin (500 mg on alternative days) which caused a marked inhibition of both thromboxane and prostacyclin production, measured this way. The possible role of altered balance of these two prostanoids in atherogenesis and diabetic angiopathy is discussed.
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PMID:Plasma thromboxane and prostacyclin metabolite ratio in atherosclerosis and diabetes mellitus. 311 17

It has been proposed that atherosclerotic arteries produce less prostacyclin (PGI2) than nonatherosclerotic arteries do, thereby predisposing arteries to vasospasm and thrombosis in vivo. We reexamined this concept by measuring spontaneous as well as arachidonate-induced PGI2 biosynthesis in aortic segments from nonatherosclerotic and cholesterol-fed atherosclerotic New Zealand White rabbits. Thromboxane A2 (TXA2) generation was also measured. Formation of PGI2, as well as TXA2, as measured by radioimmunoassay (RIA) of their metabolites, was increased in atherosclerotic aortic segments relative to nonatherosclerotic segments (P less than or equal to 0.05) at 0, 5, 10, 15, and 30 min of incubation with arachidonate. Pretreatment of arterial segments with indomethacin inhibited PGI2 as well as TXA2 formation, whereas pretreatment with the selective TXA2 inhibitor OKY-046 inhibited only TXA2 release, thus confirming the identity of icosanoids. To confirm the RIA data, aortic segments were incubated with [14C]arachidonate prior to stimulation with unlabeled arachidonate. The uptake of arachidonate was similar, but the release of incorporated [14C]arachidonate was significantly (P less than or equal to 0.05) greater in atherosclerotic segments than in nonatherosclerotic ones. Conversions of released [14C]arachidonate to 6-keto[14C]prostaglandin F1 alpha and [14C]thromboxane B2 were similar in the two types of aortic segments. Thus, synthesis of PGI2 as well as TXA2 is increased in atherosclerosis, and this alteration in arachidonate metabolism is related to increased release of arachidonate.
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PMID:Increased prostacyclin and thromboxane A2 biosynthesis in atherosclerosis. 313 16

Injury to the endothelial lining of arteries is an important mechanism in both the early and late stages of the development of atherosclerosis. Platelets can contribute to the early lesions by releasing factors that cause smooth muscle cell migration and proliferation. In the later stages, the formation of large platelet-fibrin thrombi that become organized into the vessel wall contributes to the development of focal atherosclerotic narrowing of arteries. Injury to the vessel wall can also be a factor in causing spasm of coronary arteries, particularly at sites of stenosis. The spasm may cause ischemia, anginal pain, and, in some individuals, ventricular fibrillation and death. In other individuals, the spasm may not cause death but may persist long enough for an occlusive thrombus to form and cause myocardial infarction. The events leading to thrombosis involve not only the release of arachidonic acid and the formation of TXA2, but other pathways that are independent of the arachidonate pathway. In some circumstances thrombin (which causes platelet aggregation and release that are largely independent of the arachidonate pathway and TXA2 formation) is the primary stimulus causing the initiation and growth of the thrombus. The role of products of the arachidonate pathway in causing spasm is not understood. PGI2 produced by the vessel wall could be important in preventing or minimizing coronary artery spasm. The best way to prevent the development of atherosclerosis and its clinical complications is to prevent or minimize injury of the endothelium.
Adv Prostaglandin Thromboxane Leukot Res 1985
PMID:Platelets, endothelium, and vessel injury. 315 7

Thromboxane A2 (TXA2) is mainly formed in thrombocytes. It promotes thrombocyte aggregation and contracts the blood vessels. TXA2 appears to be a specific physiological thrombotic agent. Synthesis of TXA2 is elevated in patients with diabetes mellitus of types I and II and in hypertensive patients. TXA2 has a half-life of about 30 s under physiological conditions. Prostacyclin (PGI2) is formed in the vessel walls. Its action is antagonistic to TXA2, that is, it inhibits platelet aggregation and dilates the blood vessels. Synthesis of PGI2 is depressed in the presence of the classical 4 main risk factors for atherosclerosis: arterial hypertension, hyperlipoproteinaemia, smoking and diabetes mellitus. PGI2 has a half-life of about 3 min under physiological conditions. Since TXA2 and PGI2 are very labile and thus extremely difficult to measure, it is at present usual to measure their stable metabolites thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). Radioimmunological measurement (RIA) of TXB2 in plasma requires no preliminary work, but radioimmunological measurement of 6-keto-PGF1 alpha in plasma requires prior extraction and concentrating, since the concentration of 6-keto-PGF1 alpha in the plasma is usually below the detection limit of commercial RIA kits. This paper describes standardized conditions for drawing the blood sample, a simple method of extraction from plasma, and the reliability of two commercial RIA kits with 125I tracer in measuring TXB2 and 6-keto-PGF1 alpha in plasma.
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PMID:Routine measurement of thromboxane B2 and the prostacyclin metabolite 6-keto-prostaglandin F1 alpha in plasma. 377 54


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