A study of the role of plasma thromboxane B2 and 6-keto-prostaglandin F1 alpha in epidemic hemorrhagic fever

Plasma concentrations of Thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were dynamically measured with radioimmunoassay in 30 patients of epidemic hemorrhagic fever (EHF). It was found that the levels plasma TXB2 significantly increased and 6-keto-PGF1 alpha decreased in EHF patients as compared with those in controls. The more severe the patient's condition, the higher the level of TXB2 and the lower the level of 6-keto-PGF1 alpha. The ratio of TXB2/6-keto-PGF1 alpha was parallel with the severity of the patient's condition. Plasma TXB and TXB2/6-keto-PGF1 alpha ratio increased significantly in the hemorrhagic and shock group, while 6-keto-PGF1 alpha decreased significantly in the shock group. The results showed that there is a distinct imbalance of TXA2-PGI2 mediated through the increase of TXA2 and decrease of PGI2 in EHF. The imbalance of TXA2-PGI2 participates in the pathogenesis and pathophysiology of hemorrhage, shock and renal dysfunction.     

Effects of a selective thromboxane synthetase inhibitor (OKY-046) in patients with coronary artery disease during exercise

We studied the levels of thromboxane B2 (TXB2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), platelet aggregability, beta-thromboglobulin and platelet factor 4 in 30 coronary artery disease (CAD) patients and 21 normal subjects during exercise. During treadmill exercise, 13 of 30 CAD patients reported chest pain. We administered a selective thromboxane synthetase inhibitor (OKY-046) for 2 weeks to 10 CAD patients with exercise-induced chest pain and studied its effects. At rest, the plasma TXB2 levels and platelet aggregation were significantly lower in normal subjects than in CAD patients, and there was no difference between CAD patients with and without exercise-induced chest pain. On treadmill testing, plasma TXB2 levels and platelet aggregation increased significantly only in the CAD patients with exercise-induced chest pain. Plasma 6-keto-PGF1 alpha levels in normal subjects were significantly higher than those in CAD patients both at rest and during exercise. After administration of OKY-046, mean exercise time increased significantly from 7.5 to 8.6 min (p less than 0.001). Plasma TXB2 level and platelet aggregation decreased significantly after OKY-046 administration both at rest and during exercise. These results suggest that a marked increase in TXA2, with only a minimal change in PGI2, during exercise may contribute to exercise-induced myocardial ischemia, and that OKY-046 is useful in the treatment of CAD patients.     

阻塞性睡眠呼吸暂停低通气综合征患者血栓素B26-酮-前列腺素F1α和抗心磷脂抗体检测的临床研究

目的观察阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者血栓素B2(TXB2)、6-酮-前列腺素F1α(6-K-PGF1α)和抗心磷脂抗体(ACA)的变化及经鼻持续正压通气(nCPAP)对其影响.方法选择经多导睡眠图(PSG)确诊的OSAHS患者60例为试验组,根据睡眠呼吸暂停低通气指数(AHI)、最低血氧饱和度(SaO2min)将OSAHS患者分为轻、中重度组,并设正常对照组20名,19例重度OSAHS患者接受nCPAP治疗为治疗组,用酶联免疫吸附试验(ELISA)检测各组TXB2、6-K-PGF1α和ACA,比较各试验组与对照组,治疗组治疗前、后的各项指标的差异. 结果 (1)中重度OSAHS组血浆TXB2显著高于对照组(P<0.01),nCPAP治疗后比治疗前明显下降(P<0.001);中重度OSAHS组血清抗心磷脂抗体IgG和IgM(ACA-IgG、ACA-IgM)显著高于对照组(P<0.01),nCPAP治疗后比治疗前明显下降(P<0.001);中重度OSAHS组血浆6-K-PGF1α显著低于对照组(P<0.01),nCPAP治疗后比治疗前明显升高(P<0.001);(2)TXB2、ACA与AHI呈正相关,与SaO2 呈负相关(P<0.001);而6-K-PGF1α与AHI呈负相关,与SaO2呈正相关(P<0.001). 结论 OSAHS患者易患血栓栓塞性疾病.TXB2、6-K-PGF1α和ACA在OSAHS患者血栓栓塞性疾病高发病率中起重要作用,并与夜间低氧血症密切相关;nCPAP治疗可有效逆转上述改变.     

Changes of nitric oxide and endothelin, thromboxane A2 and prostaglandin in cirrhotic patients undergoing liver transplantation

AIM: To investigate the perioperative changes of nitric oxide (NO) and endothelin (ET), thromboxane Az (TXAa) and prostaglandin (PGh) during liver transplantation in end-stage liver disease patients. METHODS: Twenty-seven patients with end-stage cirrhosis undergoing liver transplantation were enrolled in this prospective study. Blood samples were obtained from superior vena at five different surgical stages. Plasma concentrations of nitrate and nitrite were determined to reflect plasma NO levels. Plasma levels of ET-1, 6-keto-PGF1 alpha and thromboxane B2 (TXB2), the latter two being stable metabolites of PGI2 and TXA2 respectively, were measured. RESULTS: The NO level decreased significantly after vascular cross-clamping and increased significantly at 30 min after reperfusion. While the ET levels at 30 min after clamping and after reperfusion were significantly elevated. The ratio of NO/ET decreased significantly at 30 min after vascular cross-clamping and at the end of surgery. The PGI2 level and the TXA2 during liver transplantation were significantly higher than the baseline level, but the ratio of TXA2/PGI2 decreased significantly at 30 min after clamping. CONCLUSION: NO/ET and TXA2/PGI2 change during liver transplantation. Although the precise mechanism remains unknown, they may play a role in the pathobiology of a variety of liver transplant-relevant processes.     

Cyclooxygenase products and cyclic nucleotide levels with infusion of arachidonic acid, PGI2, PGE2, PGF2, and 6-keto-PGF1 in an isolated dog lung

Arachidonic acid (AA) was infused into the pulmonary artery of an isolated dog lung perfused with a physiologic salt solution. This led to elevations in pulmonary cyclic AMP and prostaglandins (PGs) including PGE2, PGF2 alpha, TXB2 (a metabolite of TXA2), and 6-keto-PGF1 alpha (a metabolite of PGI2). The elevations were prevented by PG synthesis inhibitors. A dose of PGI2 comparable to that produced from AA led to elevations in cyclic AMP. These elevations were not reduced by PG synthesis inhibitors; this indicated that the inhibitors did not reduce cyclic AMP except by inhibiting metabolism of AA. The PGE2 led to lesser elevations in cyclic AMP than did PGI2; PGF2 alpha and 6-keto-PGF1 alpha did not increase cyclic AMP. Levels of cyclic AMP were not elevated. We conclude that some of the elevation in cyclic AMP from AA was most likely from production of PGs since elevations in both were prevented by the inhibitors. However, the possibility remains that AA metabolites other than PGs also contributed to elevations in cyclic AMP. We also conclude that PGI2 most likely accounted for some of the cyclic AMP elevation from AA since PGI2 could be readily produced in amounts that elevate cyclic AMP. However, the possibility remains that PGE2, the less consistent cyclic AMP stimulators (l.e., PGF2 alpha and 6-keto-PGF1 alpha), TXA2 or TXB2, or PGs not measured in this study also contributed to the elevations in cyclic AMP from AA.     

非酒精性脂肪性肝病大鼠血浆前列环素与血栓素的变化及其与肝脏损伤的关系

目的 探讨非酒精性脂肪性肝病(NAFLD)大鼠血浆前列环素(PG12)和血栓索(TX)A2的动念变化及其与肝组织学改变之间的关系。 方法 48只模型组SD大鼠给予高脂肪高胆固醇饮食饲养,分批于第8、12、16、24周处死,24只正常饮食大鼠作对照。放射免疫法检测血浆PGI 2和TXA 2的稳定代谢产物6酮-前列环素1α(PGF1 α)和TXB2含量,光镜观察肝组织切片病理学改变。 结果 模型组大鼠8周呈现单纯性脂肪肝,12～24周从脂肪性肝炎进展至脂肪性肝纤维化。模型组大鼠血浆TXB 2在造模第8、24周分别为(52.4±3.15)ng/L和(117.7±7.47)ng/L,对照组为(41.1±1.45)ng/L,t值为9.12和31.34,P<0.01和P<0.001。 血浆PGF1 α水平在造模8、24周分别为(31.1±1.6)ng/L和(3.4±2.4)ng/L,对照组为(36.5±1.7)ng/L,t值为6.27和34.62,P<0.01和,P<0.001。模型组大鼠血浆TXB2和PGF1 α水平分别与其肝组织损伤程度呈显著正相关(r=0.537,P<0.001)及负相关(r=-0.452,P<0.01)。 结论 持续24周的高脂饮食可以成功复制大鼠NAFLD模型,模型大鼠血浆TXA 2与PGI 2平衡失调,可能参与NAFLD的发病。     

Plasma eicosanoid levels in rats with nonketotic diabetes mellitus: effect of severity

Nonketotic diabetes mellitus (DM) is associated with increased platelet production of thromboxane (TX) A2 and decreased endothelial production of prostacyclin (prostaglandin [PG]I2), but measurements of stable derivatives of these substances in the circulation have yielded discordant results. We studied the relationship between the severity of nonketotic DM and the plasma levels of 13,14-dihydro-15-keto-PGE2, 6-keto-PGF1 alpha, and TXB2 (stable derivatives of PGE2, PGI2, and TXA2, respectively) in rats, using three commonly employed doses of streptozotocin (40, 50, and 60 mg/kg body weight) to induce nonketotic DM of varying severity. Small differences in the severity of DM were associated with considerable differences in the plasma levels of 13,14-dihydro-15-keto-PGE2 and 6-keto-PGF1 alpha but not TXB2. Each eicosanoid responded differently to variations in the severity of DM. The plasma 13,14-dihydro-15-keto-PGE2 level was significantly lower than normal in the rats given 40 mg/kg streptozotocin, was unchanged from normal in the rats given 50 mg/kg and was significantly higher than normal in the rats given 60 mg/kg. The plasma 6-keto-PGF1 alpha level was significantly increased in rats given 40 mg/kg and 60 mg/kg, but was unchanged in those given 50 mg/kg. The plasma TXB2 level was not significantly different from normal in any one of the three groups of rats with nonketotic DM. The effect of severity on the plasma levels of the PGE2 and PGI2 derivatives is unexplained, but may reflect the origin of these derivatives from diverse organs and tissues, and the differing effects of abnormal metabolic factors (eg, fatty acids, glucose, insulin, pH) on the synthesis of these derivatives.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma renin activity, angiotensin II, angiotensin converting enzyme, thromboxane A2 and prostacyclin I2 levels in pigs with severe hypoxia and hypercapnea and acidosis shock]

To evaluate the role of certain plasma biosubstances on the development of pulmonary hypertension and shock during severe hypoxia, hypercapnia and acidosis, plasma renin activity (PRA), angiotensin II (ATII), angiotensin converting enzyme (ACE), TXB2 and 6-Keto-PGF1 alpha (the stable metabolites of TXA2 and PGI2) were assayed in blood from pulmonary artery and aorta in seven pigs. Pulmonary arterial pressure (PAP) was monitored via Swan-Ganz catheter. During hypoxic and hypercapnic ventilation, PaO2 dropped to 4.7 kPa, PaCO2 rose to 21.1 kPa, pH dropped to 6.82, PAP increased from 2.43 +/- 0.06 to 4.46 +/- 0.45 kPa when acidotic shock developed (all P less than 0.05). Meanwhile ATII levels rose (all P less than 0.05). PRA significantly increased during acidotic shock as compared with normal ventilation (P less than 0.02). ACE dropped significantly (P less than 0.05), TXB2 and 6-keto-PGF1 alpha showed no significant change before and after hypoxic and hypercapnic ventilation.     

Relation of arachidonate metabolites to abnormal control of the pulmonary circulation in a child

To evaluate the role of arachidonate metabolites in regulating pulmonary vascular tone, we performed multiple studies on a 17-month-old girl with idiopathic pulmonary hypertension, systemic arterial hypoxemia (due to ventilation-perfusion mismatching), and an elevated thromboxane A2 (TXA2) to prostacyclin (PGI2) ratio due to increased TXA2 (measured as their stable metabolites, TXB2 and 6-keto-PGF1 alpha, respectively). Intravenous infusions of PGI2 reduced mean pulmonary arterial pressure (from 80 to 47 mmHg), increased cardiac output (from 3.43 to 3.97 L/min), increased systemic arterial oxygen saturation (from 60 to 72 percent), and decreased the TXB2 to 6-keto-PGF1 alpha ratio (from 5.9 to 0.2); mean systemic arterial pressure was unchanged. Pharmacologically decreasing the TXB2 to 6-keto-PGF1 alpha ratio with administration of nifedipine or diltiazem also reduced pulmonary hypertension and increased systemic arterial oxygen saturation in this patient. Nifedipine and diltiazem decreased the ratio by decreasing TXB2. Prostacyclin decreased the ratio by increasing 6-keto-PGF1 alpha. These studies support the hypothesis that the balance between TXA2 and PGI2 is an important influence on pulmonary vascular tone.     

Altered renal and platelet arachidonic acid metabolism in cirrhosis

Urinary excretion rates of prostaglandin (PG) E2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane (TX) B2 were evaluated in three groups of cirrhotic patients [without ascites (group 1, 13 cases), with ascites and normal renal function (group 2, 15 cases), and with ascites and renal failure (group 3, 5 cases)] and in 14 healthy controls. All urinary arachidonate metabolites were significantly increased in group 2 patients. Patients with renal failure showed lower PGE2, PGF2 alpha, and TXB2 values than those from group 2; PGF2 alpha values were also lower than controls. Platelet TXA2 production during whole blood clotting was significantly reduced in all groups of patients. Administration of low-dose aspirin and sulindac, two cyclooxygenase inhibitors selectively sparing renal cyclooxygenase activity, effectively inhibited platelet TXA2 production without affecting urinary TXB2 excretion, thus ruling out platelets as a possible source of urinary TXB2. We conclude that patients with ascites and normal renal function show an overall activation of the renal PG system. Renal production of vasodilating PGE2 and PGI2 may be involved in supporting renal function in these patients. A reduced platelet synthesis of proaggregatory TXA2 also occurs in cirrhotic patients. This may play a role in the bleeding tendency of cirrhosis.     

Intestinal prostacyclin and thromboxane production in irreversible hemorrhagic shock

Arterial and intestinal venous blood were sampled every hour for measurement of thromboxane B2 (TXB2) and 6-keto-PGF1 alpha, stable metabolites of thromboxane A2 and prostacyclin, respectively, in dogs subjected to hemorrhagic hypotension at 32.8 +/- 1.4 mm Hg for 3 h, followed by reinfusion of the remaining shed blood. Control dogs were treated alike without hypotension. Arterial and intestinal venous TXB2 significantly increased during hypotensive and post-transfusion periods, the venous concentration being significantly higher than the corresponding arterial. The arterial and venous 6-keto-PGF1 alpha increased during hypotension but decreased during post-transfusion periods. Furthermore, arterial and venous TXB2 to 6-keto-PGF1 alpha concentration ratio increased. Intestinal TXB2 release (blood flow X arteriovenous concentration difference) increased progressively, whereas 6-keto-PGF1 alpha release decreased. No significant changes occurred in the control dogs. This study shows an imbalance in intestinal production and release of TXA2 and PGI2, in favor of TXA2 during severe hemorrhagic hypotension and after blood transfusion. The imbalance may contribute to the development of irreversible hemorrhagic shock and reperfusion injury.     

Platelet functions in patients with acute myocardial infarction

The changes of platelet functions including platelet membrane microviscosity (PMMV), plasma 5-HT, plasma TXB2 and 6-K-PGF1a were studied in 30 cases of AMI and 13 cases of unstable angina (UA), 20 normal subjects as control. After onset of AMI, PMMV, plasma 5-HT, 6-k-PGF1a all increased quickly, especially on the 1st day (P less than 0.001-0.01). During 3 weeks observation, only 6-K-PGF1a decreased to the normal level on 14th day. There were no obvious decrease of plasma TXB2, 5-HT and PMMV. It showed that in acute phase of AMI without intervention of any antiplatelet drugs the platelets were activated continuously. Plasma 5-HT was the most sensitive predictor for the severity of AMI as observed by the comparison between the cases with complications and serum peak CK greater than 1000 U/L, and those without complications and peak CK less than 1000 U/L (P less than 0.001-0.05). The great change of PMMV was a bad prognosis. In patients with UA, during acute myocardial ischemia, the platelets were also activated significantly, but the extent was not as high as that in AMI.     

Production of thromboxane A2 and prostaglandin i2 affected by interaction of heat aggregated IgG,endothelial cells,and platelets in lupus nephritis

OBJECTIVE: To examine the role of immune complexes in the prostanoid metabolism of glomerular capillary endothelial cells (EC) and platelets in lupus nephritis. Heat aggregated IgG (HA-IgG), instead of immune complexes, was incubated using an in vitro coculture system with human umbilical vein EC, instead of glomerular capillary EC, and platelets. The effect of complement component C1q and a novel imidazole-type thromboxane A2 (TXA2) synthetase inhibitor, DP-1904, on this prostanoid metabolism change was also investigated. METHODS: EC monolayers (1.5x10(5) cells/well) were incubated with various concentrations of HA-IgG, monomeric IgG, or medium alone for 1 h at 37 degrees C, and then incubated with platelet suspensions (1x10(8) cells/ml) for various times. Concentrations of TXB2 and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), the stable hydrolysis products of TXA2 and prostaglandin I2 (PGI2), respectively, released in the supernatants were measured by ELISA. RESULTS: HA-IgG bound to EC monolayers produced TXB2 and 6-keto-PGF(1alpha) in a concentration dependent manner and much more than monomeric IgG or medium alone did. However, the production of 6-keto-PGF(1alpha) stimulated with HA-IgG was much lower than that of TXB2, indicating a large imbalance between TXA2 and PGI2. Preincubation of HA-IgG with purified C1q partially suppressed the production of TXB2, but not that of 6-keto-PGF(1alpha). DP-1904 suppressed the production of TXB2 completely, but by sharp contrast, it dramatically increased the production of 6-keto-PGF(1alpha) from EC and platelets by HA-IgG. CONCLUSION: The large imbalance of TXA2 and PGI2 produced by the interaction of EC, immune complexes, and platelets may be associated with alterations in glomerular pathological findings and hemodynamics mediated by immune complexes in lupus nephritis. C1q and a TXA2 synthetase inhibitor may improve the abnormal prostanoid metabolism change of lupus nephritis.     

Effect of single-dose aspirin on TXA2 and PGI2 cyclooxygenases in vivo

The present study investigated the sensitivities of the thromboxane A2 (TXA2) cyclooxygenase and the prostacyclin (PGI2) cyclooxygenase to aspirin using an in vivo animal model. In this model, arachidonic acid (AA) was administered to mice via cardiac puncture, and plasma levels of thromboxane B2 (TXB2) and 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) were determined. Infusion of AA (5, 10, 25 and 50 mg/kg) resulted in a dose-dependent increase in both TXB2 and 6-keto PGF1 alpha. Pretreatment with aspirin resulted in a dose-dependent and parallel decrease in TXB2 and 6-keto PGF1 alpha production. This nonselective inhibition occurred at all doses of aspirin (1, 10 and 50 mg/kg) and at all levels of cyclooxygenase activity (5-50 mg/kg AA). These results indicate that the TXA2 and PGI2 cyclooxygenase enzymes are equally sensitive to inhibition by a single dose of aspirin.     

Reduction of prostacyclin synthesis as a possible cause of transient flow reduction in a partially constricted canine coronary artery

Coronary blood flow decreases cyclically in a partially occluded coronary artery of anesthetized dogs. Spontaneous aggregation and deaggregation of platelet plugs in the constricted artery have been indicated to be responsible for this phenomenon. A current hypothesis is that platelet aggregation may be determined by a balance between proaggregatory platelet product, thromboxane A2 (TXA2), and antiaggregatory substance, prostacyclin (PGI2). To elucidate the relationship between the cyclical reduction of coronary flow (CRCF) and metabolic alterations of TXA2 and PGI2, we attempted to determine the plasma levels of their stable catabolites, thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), in the coronary circulation of 69 dogs. Of 40 cases, 20 cases exhibited CRCF accompanying a significant increase in TXB2 in the coronary sinus (CS) (P less than 0.05) and constant levels of 6-keto-PGF1 alpha in the CS and aorta (Ao). Another 20 cases did not exhibit CRCF that accompanied a marked increase in 6-keto-PGF1 alpha (P less than 0.05) with virtually no change in TXB2 in the CS and Ao. A higher dose of indomethacin (10 mg/kg, i.v.) was capable of evoking CRCF in cases not exhibiting CRCF spontaneously. Under these conditions, a significant decrease in 6-keto-PGF1 alpha was seen both in the CS and Ao compared with lower doses of indomethacin (1 to 3 mg/kg, P less than 0.01), that produced less pronounced reduction of 6-keto-PGF1 alpha without CRCF. Intravenous infusion of PGI2 (0.1 microgram/kg/min.) completely abolished spontaneously and indomethacin-induced CRCF with a marked elevation of 6-keto-PGF1 alpha in the CS and Ao. Although OKY-1580, a TXA2 synthetase inhibitor, relieved spontaneously-evoked CRCF with a marked increase in 6-keto-PGF1 alpha and a slight reduction of TXB2, indomethacin-induced CRCF was not abolished by this agent. These results are consistent with the hypothesis that the reduction of endogenous PGI2 synthesis in the vascular wall is related to the occurrence of CRCF after partial constriction of coronary artery and indomethacin.     

The hypertensive response to vasopressor agents stimulates the release of thromboxane A2 in hypercholesterolaemic rabbits

The production of thromboxane A2 (TXA2) and prostacyclin (PGI2) is altered in hypercholesterolaemia. The purpose of this study was to investigate the effect of an acute rise in arterial pressure produced by pressor agents on the release of TXA2 and PGI2 in hypercholesterolaemic rabbits. Hypercholesterolaemia was induced in rabbits by feeding pellet food containing 1% cholesterol for 3 months. Administration of pressor agents (ergonovine 0.5-2.0 mg.kg-1, noradrenaline 5.0-20.0 micrograms.kg-1 and angiotensin-II 0.5-2.0 micrograms.kg-1) increased arterial pressure dose dependently, accompanied by a pressure dependent increase in the plasma concentrations of both TXB2 and 6-keto-PGF1 alpha (stable metabolites of TXA2 and PGI2) in control rabbits, but only of TXB2 in hypercholesterolaemic rabbits. In control rabbits the maximum increase in TXB2 was 51% with ergonovine, 73% with noradrenaline, and 51% with angiotensin-II; and the maximum increase in 6-keto-PGF1 alpha was 48% with ergonovine, 76% with noradrenaline, and 198% with angiotensin-II. In hypercholesterolaemic rabbits the maximum increase in TXB2 was 130% with ergonovine, 144% with noradrenaline, and 128% with angiotensin-II. The pressor induced increase in TXB2 was suppressed when the increase in arterial pressure was counteracted by the concomitant administration of vasodilators (glyceryl trinitrate 40 micrograms.kg-1.min-1 and verapamil 20 micrograms.kg-1.min-1) in both control and hypercholesterolaemic rabbits. Neither TXB2 biosynthesis nor phospholipase A2 activity in platelets was affected by ergonovine, noradrenaline or angiotensin-II in vitro. These results suggested that the acute rise in arterial pressure caused by these pressor agents increased TXA2 release in vivo and that the increase was greater in hypercholesterolaemic than in control rabbits.     

Changes of thromboxane A2 (TXA2) and prostacyclin (PGI2) in COPD patients with pulmonary hypertension

We measured the pulmonary arterial pressure and the level of Thromboxane A2 (TXA2), and Prostacyclin (PGI2) in 30 stable COPD patients and the level of TXA2 and PGI2 in 10 normal subjects so as to investigate the changes of TXA2 and PGI2 in COPD patients with pulmonary hypertension. The results showed that the level of TXA2 increased significantly in COPD patients with dominant and latent pulmonary hypertension when compared with that in normal subjects (P less than 0.001, less than 0.01), and the level of TXA2 in COPD patients with dominant pulmonary hypertension was also higher than that in COPD patients with latent pulmonary hypertension (P less than 0.02), but there was no difference in the level of PGI2 among normal subjects and COPD patients with or without pulmonary hypertension. This indicates that TXA2 plays an important role in causing pulmonary hypertension in COPD patients.     

Effect of OKY-046, a thromboxane A2 synthetase inhibitor, on arachidonate-induced platelet aggregation: possible role of "prostaglandin H2 steal" mechanism

To clarify the mode of action of a selective thromboxane A2 (TXA2) blockade in platelet reactivity, we examined the effect of (E)-3-[4-(1-imidazolylmethyl) phenyl]-2-propenoic acid hydrochloride (OKY-046), a potent TXA2 synthetase inhibitor, on human platelet aggregation induced by arachidonic acid (1 mM) in the absence and presence of aspirin-treated aortic microsomes containing prostacyclin (PGI2) synthetase activity ex vivo. The production of TXA2 and PGI2 in platelet rich plasma was determined by the amounts of their stable catabolites, TXB2 and 6-keto-PGF1 alpha respectively, measured by radioimmunoassay. In the absence of aortic microsomes, OKY-046 (greater than 10(-5) M) produced more than 90% inhibition of TXA2 production, whereas platelet aggregation was less inhibited, about 40% inhibition over control, by OKY-046 in that concentration. In the presence of aortic microsomes, the inhibitory effect of OKY-046 on platelet aggregation was markedly augmented in a dose-dependent manner in proportion to the increment of PGI2 production, which paralleled the OKY-046-induced inhibition of TXA2. These results suggest that a selective TXA2 blockade produces effects on platelet aggregation mainly in dual fashion in the presence of PGI2 synthetase: one is due to mere inhibition of TXA2 synthetase and the other is due to the enhancement of PGI2 production probably involving "prostaglandin H2 (PGH2) steal" mechanism, in which PGH2 accumulated in platelets is partly converted to a substrate of PGI2 synthetase in aortic microsomes to produce PGI2.     

Changes in parameters of hemorheology and circulation 6-keto-PGF1 alpha and TXB2 in dilated cardiomyopathy

The changes in 12 parameters of hemorheology were observed and the levels of peripheral plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) measured in 35 cases of dilated cardiomyopathy (DCM), including 6 peripartum cardiomyopathy (PCM). We found that there is of hyperviscosity in DCM, the causes were decrease of erythrocyte deformability, increase of red blood cell aggregation, increase of plasma fibrinogen and TXA2 level and decrease of plasma 6-keto-PGF1 alpha level.     

血小板活化在哮喘发病中的意义

目的　探讨血小板活化在哮喘发病中的作用。方法　利用酶联免疫法及流式细胞仪分别测定 6 2例哮喘患者和 18名正常对照者血浆 11 去氢血栓烷B2 (11 DH TXB2 )、血栓烷 (TXB2 )浓度和血小板膜CD 6 2P的表达情况 ,并利用荧光酶联免疫法测定部分血清嗜酸细胞阳离子蛋白 (ECP)水平。结果　症状性哮喘组血浆 11 DH TXB2 浓度为 (33 2± 2 7)ng/L ,血小板CD 6 2P阳性百分比为 (2 3 8±3 0 ) % ,平均荧光强度为 2 75± 0 2 9;与健康对照组和缓解组比较差异有显著性 (P分别 <0 0 1、<0 0 5 )。缓解期哮喘与健康对照组比较仅血浆 11 DH TXB2 浓度差异有显著性 (P <0 0 5 )。哮喘发作时血小板活化水平与血清ECP及一秒钟用力呼气容积占预计值百分比 (FEV1占预计值百分比 )、最大呼气流量 (PEF)相关。结论　哮喘发作时存在血小板的异常活化 ,其活化程度与哮喘气道炎症及病情有一定相关性 ,血小板可能通过影响嗜酸细胞功能参与哮喘的发病