Salutary actions of thromboxane synthetase inhibition during global myocardial ischemia

Summary Isolated cat hearts were perfused with blood-free Krebs-Henseleit solution for 165 min. Ischemia was induced by reducing perfusion to 0.02 ml/min/g wet heart weight for 2h followed by reperfusion at controls flows for 30 min. Hearts perfused with the thromboxane synthetase inhibitor OKY-1581 at concentrations of 5×10^–6 M were spared from the increases in circulating thromboxane B₂ occurring in untreated ischemic hearts. After reperfusion, cardiac contractile force increased to a higher level in OKY-1581 treated hearts. This was associated with a lower coronary vascular resistance than in untreated ischemic hearts. OKY-1581 treated ischemic hearts exhibited lower perfusate and higher myocardial creatine kinase (CK) activity than untreated ischemic hearts, indicative of preservation of cellular integrity. Also, OKY-1581 treated ischemic hearts showed improved lysosomal stability as evidenced by a lower tissue percent free cathepsin D activity than untreated ischemic hearts. These results are consistent with a significant role of thromboxanes in the propagation of myocardial cellular damage during ischemia.Supported in part by research grant 1 RO1 HL 25575-01 A1 from the National Heart Lung and Blood Institute of the NIH     

Bradykinin-induced release of thromboxane B2 into bronchoalveolar lavage fluid of guinea pigs: relationship to airflow obstruction

The aim of this study was to evaluate the role of thromboxane A₂ in bradykinin-induced airflow obstruction in guinea pig in vivo. Airway insufflation pressure (P_i) was measured to assess airflow obstruction and the thromboxane B₂ (a stable metabolite of thromboxane A₂) concentration in bronchoalvelolar lavage fluid was determined by radioimmunoassay. The animals were pretreated with propranolol (1 mg/kg i.v.) and suxamethonium (5 mg i.v.) prior to bradykinin administration. Bradykinin instillation into the trachea (300 nmol) induced a P_i increase (47.5 ± 8.3 cm H₂O versus 23.8 ± 1.5 in sham) and significant thromboxane B₂ release into bronchoalveolar lavage fluid (79 ± 19 pg/ml versus 19 ± 6 in sham). A thromboxane synthase inhibitor (OKY-046, 30 mg/kg i.v.; ((E-E)-3-[p(1H-imidazole-1-yl-methyl) phenyl]-2-propenoic acid hydrochloride mono-hydrate)) or a thromboxane A₂ receptor antagonist (ICI192,605, 0.5 mg/kg i.v.; (4-(Z)-6-(2-o-chloro-phenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl)hexenoic acid)) reduced the P_i increase evoked by bradykinin (38.7 ± 3.8 and 40.6 ± 3.8 cm H₂O, respectively). OKY-046 abolished the thromboxane B₂ release. A platelet-activating factor receptor antagonist, WEB2086 (1 mg/kg i.v.; (3-[4-(chlorophenyl)-9-methyl-6H-thienol [3,2-f][1,2,4]trizolo-[4,3-a][1,4] diazepin-2-yl]1-4-(4-morpholinyl)-1-propanon) did not significantly affect any measured parameter. We conclude that, in guinea pigs, bradykinin-induced airway effects are associated with a local thromboxane A₂ release.     

Preventive effect of the thromboxane A2 receptor antagonist S-1452 (d-s-145 Ca) on arachidonate-induced sudden death and cerebral infarction in rabbits

The thromboxane A₂ (TXA₂) receptor antagonist S-1452, d-S-145 Ca, calcium 5(Z)-1R,2S,3S,4S-7-[3-phenylsulfonylaminobicyclo[2.2.1]hept-2-yl]-5-heptenoate dihydrate, prevented sudden death induced by arachidonate or U46619 in rabbits when given in a dose range between 0.1 mg/kg and 1 mg/kg, p.o. OKY-046 and aspirin were also effective in this thromboembolism model, but 10 to 30 times larger doses were needed. Orally administered S-1452 successfully prevented the incidence of cerebral infarction in the rabbit, which was elicited by infusion of 10 mg/ml sodium arachidonate at a rate of 0.1 ml/min for 30 min via a left internal carotid artery. Significant reduction of the infarction grade was observed in dosing above 3 mg/kg of this compound 1 to 4 h before the arachidonate infusion. OKY-046 was effective similarly, but less active than S-1452 (the minimum effective dose: 10 mg/kg). Ticlopidine and aspirin were entirely inactive in this model even after much larger doses. S-1452 is a useful compound for prevention of TXA₂-mediated thrombosis in the brain. © 1993 wiley-Liss, Inc.     

Effects of thromboxane synthase inhibitors on renal function

Summary In general the effects of thromboxane A₂(TXA₂) on renal function are opposite those produced by other prostanoids. TXA₂ synthase inhibitors decrease the biosynthesis of TXA₂ and may increase the production of other prostanoids by causing endoperoxide shunting. Therefore, in situations of increased kidney arachidonate mobilization, inhibition of renal TXA₂ synthase might alter renal function by reducing TXA₂ production and/or increasing prostaglandin (PG) biosynthesis. This hypothesis was tested by comparing the changes in renal function induced by suprarenal aortic constriction in anesthetized dogs pretreated with either a TXA₂ synthase inhibitor (UK 38,485; n = 7 or OKY1581; n = 7) or vehicle (0.1 M Na₂CO₃; n = 9). Several renal function parameters were compared in control versus treated animals by analysis of variance. Neither UK38,485 (1 mg/kg, i. v.) nor OKY 1581 (10 mg/kg, i. v.) significantly altered renal artery hypotension-induced changes in mean arterial blood pressure, heart rate, renal blood flow, renal vascular resistance, glomerular filtration, filtration fraction, urine flow rate, sodium excretion rate, fractional sodium excretion, potassium excretion, or fractional potassium excretion. However, both UK 38,485 and OKY 1581 seemed to attenuate the increase in renal renin secretion rate induced by suprarenal aortic constriction. We conclude that acute administration of TXA₂ synthase inhibitors does not modify acute renal artery hypotension-induced changes in either electrolyte excretion or renal hemodynamics. However, acute administration of TXA₂ inhibitors attenuates suprarenal aortic constriction-induced increases in renin release in anesthetized dogs by unknown mechanisms. Send offprint requests to E. K. Jackson     

去氢紫堇碱对兔血小板TXB2及主动脉6-keto-PGF1PGF1α含量的影响

Dehydrocorydaline (DHC) was shown to reduce the production of thromboxane B₂ (TXB₂)in platelets and 6-keto-prostaglandin F_1α (6-keto-PGF_1α in the aorta of rabbits in vitro. The effect of DHC increased with the increase of dose.DHC 0.41 mg was found to inhibit the formatiom of TXB₂ markedly while not reduce the content of 6-keto-FCF_1α. DHC also exhibited obvious inhibitory effect on the arachidonic acid (0.66mmol/L) induced formation of platelet malondialdehyde (MDA). These effects were similiar to the specific cycloxygenase inhibitor, aspirin (0.03 mg/ml). The results suggest that (1) DHC reduced both contents of TXA₂ and PGI₂ in vitro. (2) DHC markedly inhibited the system of cycloxygenase in cell microsomes. (3) As to whether TXA₂ synthetase or cycloxygenase was inhibited in these experiments is still to be elucidated.     

L8027 and 1-nonyl-imidazole as non-selective inhibitors of thromboxane synthesis

The inhibition of prostaglandin-related actions on the platelets, respiration and hemodynamics of guinea pigs by 1-(isopropyl-2-indolyl)-3-pyridyl-3-ketone (compound L8027) and by 1-nonyl-imidazole (NI) was studied. L8027 (1–10 μg/kg, i.v.) inhibited arachidonic acid (AA)-initiated bronchoconstriction, thrombocytopenia and hypotension in a dose-dependent and reversible manner. NI, however, in doses as high as 8 mg/kg did not inhibit these actions. AA-induced platelet aggregation was antagonized by L8027 (50–500 nM) and NI (25–100 μM), and this action was dose-dependent and competitive. Thromboxane A2 (TxA2) synthesis in blood and platelets, as measured by the rabbit aorta bioassay, was suppressed in a concentration-related manner by L8027 at anti-aggregatory doses. NI did not inhibit TxA2 synthesis in guinea-pig platelet-rich plasma (PRP) at concentrations which blocked platelet aggregation. However, it did block TxA2 synthesis in rabbit and human PRP and in washed guinea-pig platelets, indicating a species or plasma specificity. Both compounds inhibited ATP release from platelets as they inhibited aggregation. The radioimmunoassay revealed that L8027 decreased formation of both TxB2 and PGE2, unlike imidazole which only blocked formation of TxB2 and resulted in an increase of PGE2. These results show that although L8027 does block TxA2 formation, it is not a selective antagonist and it inhibits cyclo-oxygenase as well. NI appears to have the ability to act via mechanisms other than prostaglandin metabolism.     

Dual effects of 5-hydroxytryptamine on stable analogue of thromboxane A~(2~_) induced aggregation and release reaction in rabbit platelets

目的：研究５ＨＴ对ＳＴＡ２血小板聚集和释放反应的影响及可能的分子机制．方法：以透光法，介质中ＡＴＰ含量及荧光图像法评价血小板变形，聚集反应和［Ｃａ２］ｉ水平．结果：（１）５ＨＴ预处理可消除ＳＴＡ２的血小板变形，ＳＴＡ２０３μｍｏｌ·Ｌ－１的聚集增强，ｌ－３μｍｏｌ·Ｌ－１的聚集不变，释放反应抑制．（２）５ＨＴ预处理增加ＳＴＡ２０３μｍｏｌ·Ｌ－１的［Ｃａ２＋］ｉ，降低３μｍｏｌ·Ｌ－１的［Ｃａ２＋］ｉ降低．（３）延长加入５ＨＴ和ＳＴＡ２的间隔，ＳＴＡ２０３μｍｏｌ·Ｌ－１的聚集增强，３μｍｏｌ·Ｌ－１的聚集不变，释放反应抑制．结论：５ＨＴ对ＳＴＡ２介导的聚集和释放反应有双重影响．对ＳＴＡ２［Ｃａ２＋］ｉ的调节可能是上述反应的分子机制．     

Patents on bacterial tRNA synthetase inhibitors: January 1996 to March 1999

This review focuses on patents published between January 1996 and March 1999 covering bacterial tRNA synthetase inhibitors as antibacterial agents. Nine of the eleven patents issued during this period claim new formulations, forms and uses as well as new derivatives of pseudomonic acid A (mupirocin, SmithKline Beecham), a natural product inhibitor of isoleucyl-tRNA synthetase. One patent describes a new use for indolmycin, an inhibitor of tryptophanyl-tRNA synthetase, and another discloses a novel class of isoleucyl-tRNA synthetase inhibitors.     

ONO-3708和S-145对STA_2介导的家兔血小板变形和聚集反应的抑制作用(英文)

目的:评价ONO-3708和S-145对血小板变形和聚集反应的不同抑制模式。方法:以透光度法测量血小板变形和聚集反应,荧光图像分析法测量单细胞内游离钙的变化。结果:(1)STA_2的聚集反应可被依他酸,ONO-3708和S-145抑制(P<0.01),血小板变形仅被S-145抑制。(2)S-145的抑制作用随孵育时间延长而增强,ONO-3708不变。(3)洗脱后ONO-3708的作用消失,而S-145抑制作用依然存在。(4)STA_2的细胞内游离钙动员部分被ONO-3708和依他酸取消(P<0.01),但可被S-145完全抑制。结论:S-145和ONO-3708分别作用于血小板TXA_2受体的不同结合位点。     

丹酚酸B镁盐对兔洗涤血小板聚集和5-HT释放反应的影响(英文)

AIM: To study the effects and mechanism of magnesium lithospermate B(MLB) on rabbit platelet aggregation and 5-HT release. METHODS: The platelet aggregation was determined by Born's method. Release of serotonin (5-HT) and formation of thromboxane A2 (TXA2) were measured by fluorophotometry and radioimmunoassay (RIA) respectively. Cytoplasmic free Ca2+ concentration ([Ca2+]i) in platelets was measured by Fura 2-AM fluorescence technique. RESULTS: In washed platelets, thrombin (200 U/L) or arachidonic acid (AA) (30 mumol/L)-induced aggregation was inhibited by MLB 50-800 mg/L in a concentration-dependent manner. In addition, MLB had more inhibitory effects on platelet aggregation in the absence of extracellular calcium with IC50 of 102 mg/L than in the presence of CaCl2 1 mmol/L with IC50 of 194 mg/L. MLB concentration-dependently decreased the thrombin-activated release of 5-HT, whereas it did not affect the formation of TXA2 in platelets. Furthermore, MLB not only inhibited the rise of [Ca2+]i in thrombin stimulated platelets, but decreased the [Ca2+]i in resting platelets. CONCLUSION: MLB inhibited the aggregation and 5-HT release in rabbit platelets and it is probably by attenuating intracellular calcium concentration.     

Effects of 5-HT released from platelets on thrombin-induced aggregation and ATP release in rabbit pla

Ｅｆｅｃｔｓｏｆ５ＨＴｒｅｌｅａｓｅｄｆｒｏｍｐｌａｔｅｌｅｔｓｏｎｔｈｒｏｍｂｉｎｉｎｄｕｃｅｄａｇｇｒｅｇａｔｉｏｎａｎｄＡＴＰｒｅｌｅａｓｅｉｎｒａｂｂｉｔｐｌａｔｅｌｅｔｓｉｎｖｉｔｒｏＬＩＢａｉＹａｎ１，ＬＩＷｅｎＨａｎ（Ｄｅｐａｒ...     

Inhibitiory effects of procainamide on rabbit platelet aggregation and thromboxane B_2 production in vitro

目的：研究普鲁卡因胺（ＰＡ）对凝血酶诱导血小板聚集和血栓素Ｂ２（ＴＸＢ２）产生的影响．方法：用比浊法和放射免疫分析法．结果：普鲁卡因胺８５，３４，１３６和５４４μｍｏｌ·Ｌ－１有明显抑制作用．抑制率分别为４５％±３７％，４８％±３２％，８８％±２３％，９２％±１５％和５３％±２４％，６５％±２６％，９０％±６％，９５％±６％．ＰＡ的浓度与血小板聚集和ＴＸＢ２产生的抑制效力之间，以及血小板聚集抑制率和ＴＸＢ２产生的抑制率之间均存在着正相关关系，三者的线性方程和主要参数为：＾Ｙ＝０２０７５Ｘ－４９１５７，ｒ＝０９９８５；＾Ｙ＝０９５４６Ｘ－３４６７２４，ｒ＝０９９２１；＾Ｙ＝０８２０２Ｘ＋１９７０６２，ｒ＝０９９２１．结论：普鲁卡因胺抑制凝血酶诱导血小板聚集和ＴＸＢ２产生．     

槲皮素对血小板聚集和胞浆游离钙的影响(英文)

目的:研究槲皮素对凝血酶诱导的血小板聚集和胞浆游离钙浓度的影响及钙对槲皮素的血小板聚集抑制效应的作用。方法:用荧光钙离子指示剂观察槲皮素对血小板胞浆游离钙的影响.结果:槲皮素明显抑制凝血酶诱导的血小板聚集和游离钙的升高.IC_(50)和95％可信区间分别为146.2(92.4～231.3)和78.5(49.5—124.4)μmol·L~(-1).槲皮素对血小板的抑制作用可被钙翻转.槲皮素对凝血酶诱导的钙释放无影响.结论:抑制钙内流是槲皮素抑制血小板聚集和[Ca~(2 )]_i升高的机制.     

粉防己碱对兔血小板聚集和血小板活化因子生成的影响(英文)

目的:探讨粉防己碱(Tet)对兔血小板聚集和PAF生成的影响.方法:卡西霉素(Cal)和PAF诱导血小板聚集的聚集率和Tet对血小板聚集的抑制率被测定;给予或未给予Tet处理之血小板用Cal刺激释放PAF的量也被测定.结果:在4—64 μmol·L~(-1)浓度范围,Tet明显抑制Cal和PAF诱导的血小板聚集.IC_(50)值分别为8.6μmol·L~(-1)和14.0μmol·L~(-1).Tet也浓度依赖性的抑制Cal诱导血小板释放PAF,IC_(50)值为21.0μmol·L~(-1).结论:Tet抑制血小板聚集作用与抑制内源性PAF生成有关.     

MK-447对兔血小板中胶原、ADP及血栓素A_2稳定类似物诱导的血小板变形、聚集和腺苷三磷酸释放的影响

目的:研究MK-447对胶原、ADP及血栓素A_2稳定类似物(STA_2)诱导的血小板变形、聚集和释放反应的影响。方法:浊度法评价血小板变形和聚集反应,测定富含血小板血清中ATP的量确定释放反应。结果:(1)MK-447诱导血小板变形,不被吲哚美辛抑制。预置MK-447可使胶原、ADP及STA_2的血小板变形能力下降,时程延长。(2)MK-447抑制胶原的聚集反应,并使ADP和STA_2聚集增强。(3)胶原和STA_2的释放反应可被MK-447抑制和增强。MK-447对STA_2的作用与S-145无关。结论:血小板变形在其激活早期发挥重要作用。MK-447诱导血小板变形,并对不同聚集剂的作用表现为抑制和增强的双重影响。     

Enhancement of ADP-induced aggregation by 5-HT in rabbit platelets

目的：研究５ＨＴ对ＡＤＰ介导的血小板聚集反应的增强作用．方法：以透光法、图像法和受体结合法评价聚集反应、单细胞内钙和三磷酸肌醇的含量．结果：５ＨＴ（００３－３μｍｏｌ·Ｌ－１）浓度依赖性地引起ＰＲＰ的透光度降低（ＤＬＴ），电镜结果显示血小板变形的同时伴有颗粒中心化，无聚集和释放反应．Ｆｕｒａ２负载后，５ＨＴ升高［Ｃａ２＋］ｉ，９０秒达峰值，ＩＰ３一过性升高．ＡＤＰ同样引起ＤＬＴ，但可被５ＨＴ消除，呈浓度依赖性．ＡＤＰ的聚集反应和［Ｃａ２＋］ｉ动员则由于５ＨＴ预处理而升高．结论：５ＨＴ增强ＡＤＰ的聚集反应与５ＨＴ的细胞内钙动员及ＡＤＰ的外钙内流两者的叠加作用有关．     

噻氯匹定对血小板血栓烷B_2生成的影响

口服噻氯匹定(ticlopidine)能抑制胶原诱导的血小板血栓烷B_2(TXB_2)生成。大剂量(500mg/d)可使TXB_2生成很快降低,停药1wk后恢复正常。给小剂量(250mg/d)时TXB_2的减少出现较晚,恢复亦快。噻氯匹定对ADP诱导的血小板TXB_2生成也有显著抑制作用。噻氯匹定的抗血小板作用至少有部分与抑制花生四烯酸的代谢有关。     

Effects of protein kinase C inhibitors on thromboxane production by thrombin-stimulated platelets

The purpose of these studies was to identify a possible role for protein kinase C in thromboxane production. The effects of four putative protein kinase C inhibitors were studied with platelet stimulation by thrombin (0.5-150 nM), Thrombin Quick I (1.5-500 nM) or a thrombin receptor (protease activated receptor-1) agonist peptide (TRAP) (5-120 microM). Thromboxane production was increased by the bisindolylmaleimide derivative, 2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimi de (GF 109203X), unchanged by the inhibitors 12-(2-cyanoethyl)-6,7, 12,13-tetrahydro-13-methyl-5-oxo-5H-indolo (2,3-a) pyrrolo (3, 4-c)-carbazole (G? 6976) and 5,21:12,17-dimetheno-18H-dibenzo[i, o]pyrrolo[3,4-l][1,8]diazacyclohexadecine-18,20(19H)-dione, 8-[(dimethylamino)methyl]-6,7,8,9,10,11-hexahydro-, monomethanesulfonate (379196), the latter of which is protein kinase C beta-selective, and decreased by 1-[6-[(3-acetyl-2,4, 6-trihydroxy-5-methylphenyl)methyl]-5,7-dihydroxy-2, 2-dimethyl-2H-1-benzopyran-8-yl]-3-phenyl-2-propen-1-one (rottlerin), an inhibitor selective for protein kinase C delta. These results indicate complex regulation of thromboxane synthesis in human platelets including a probable role for protein kinase C delta. The results taken together further suggest that GF 109203X may suppress negative feedback resulting from an unidentified kinase and that the classical protein kinase C isoforms alpha and beta do not have a significant role in regulating thromboxane production by platelets.     

MK-447对家兔凝血酶诱导的血小板聚集,ATP释放及细胞内游离钙动员的影响(英文)

目的:研究MK-447对家兔凝血酶诱导的血小板聚集释放反应及单细胞内钙水平的影响.方法:利用浊度法及测定PRP中ATP的含量评价聚集和释放反应,以荧光图像法分析细胞内钙浓度.结果:MK-447仅使兔多血小板血浆(PRP)透光度降低(DLT),即血小板变形,单血小板[Ca~(2 )]_i轻度增加(160 nmol·L~(-1)),并不被依他酸3 mmol·L~(-1)抑制.MK-447消除凝血酶诱导的DLT,聚集和ATP释放增强,呈剂量依赖性,且凝血酶介导的[Ca2 ]_i由369 ±45 nmol·L~(-1)增加到621±121 nmol·L~(-1).结论:MK-447的血小板变形与其[Ca~(2 )]_i释放有关.MK-447增强凝血酶的血小板聚集和ATP释放.MK-447的这一作用可能于[Ca2 ]_i的协同作用有关.