Selective conjugated fatty acids inhibit guinea pig platelet aggregation

Conjugated linoleic acids have been shown to reduce eicosanoid release from select tissues and/or cells. To elucidate effects of conjugated linoleic acid isomers on cyclooxygenase-1 (COX-1) activity and their application as platelet aggregation inhibitors, conjugated linoleic acid isomers and conjugated nonadecadienoic acid were incubated with ovine COX-1 and Raw264.7 macrophage to examine their effects on COX-1 activity. The effects were further examined in collagen and ADP-induced guinea pig whole blood platelet aggregation. Fatty acids tested were shown to inhibit COX-1 enzymatic activity. However, only 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid inhibited collagen and ADP-induced platelet aggregation with IC(50) 125.9 microM (74.2 microM to 213.4 microM, 95% confidence interval), 99.3 microM (52.8 microM to 187.2 microM, 95% confidence interval) and 124.3 microM (85.1 microM to 181.5 microM, 95% confidence interval) respectively in collagen-induced aggregation. TxB(2) release was also appreciably inhibited by 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid. Based on these data, we conclude 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid are platelet aggregation inhibitors while 9c, 11t-conjugated linoleic acid is a moderate inhibitor and linoleic acid, and 9c, 11c-conjugated linoleic acid have no effect on whole blood platelet aggregation.     

Drug-induced inhibition of guinea pig platelet aggregation unrelated to their beta-adrenolytic actions

Inhibitory actions on adenosine diphosphate (ADP)-induced platelet aggregation of atenolol, dl- and d-D-32, IPS-339, pindolol and propranolol were investigated in guinea pigs for the purpose of obtaining a clue about a possible mechanism for the disaggregatory phenomenon of beta-adrenoceptor blocking agents. The effects of verapamil and procaine on guinea pig platelet aggregation were also examined. All of these agents including verapamil and procaine showed a dose-dependent inhibitory effect on platelet aggregation, and their relative potencies determined on the basis of the molar concentrations producing a 50% inhibition of ADP-induced aggregation were in descending order: IPS-339 greater than propranolol greater than verapamil greater than dl-D-32 not equal to d-D-32 greater than pindolol greater than procaine greater than atenolol. This order of relative potencies of the inhibitory actions of these test compounds on platelet aggregation was well correlated to those of local anaesthetic action in guinea pigs (r = 0.932, P less than 0.01) and lipophilicity (r = -0.899, P less than 0.01), while it did not agree with the orders of potency of beta-adrenoceptor blocking action, intrinsic sympathomimetic action and vasodilator action. From these results, it may be reasonable to propose that inhibitory actions of beta-adrenoceptor blocking agents and local anaesthetics on platelet aggregation are caused through the same mechanism or through a very similar one.     

维拉帕米对糖尿病病人体外血小板聚集的影响

糖尿病Ⅱ型病人２０例（男性１０例，女性１０例，年龄５８±ｓ７ａ）在０．５μｍｏｌ／ＬＡＤＰ作为血小板致聚条件下加入０．２５－１．０μｍｏｌ／Ｌ维拉帕米，观察对体外血小板聚集的影响。结果表明糖尿病Ⅱ型病人在二相聚集比正常者显著增强，维拉帕米在０．２５－１．０μｍｏｌ／Ｌ浓度范围内均可部分减缓糖尿病Ⅱ型病人所增高的血小板聚集。     

Effect of some acetylcholinesterase reactivators on human platelet aggregation in vitro

Acetylcholinesterase (AChE) reactivators are employed for the prophylaxis and treatment of intoxications with organophosphorus AChE inhibitors, including nerve agents and pesticides. For the recovery of inhibited enzyme, derivatives from the group of pyridinium or bispyridinium aldoximes (called oximes) are used. Adverse effects of these substances are not well elucidated, because of their narrow and one-shot usage. Owing to this fact, the study evaluated the influence of some currently applied oximes on human platelet aggregation in vitro. The antiplatelet activity of pralidoxime, obidoxime, HI-6, methoxime and HL? 7 was assayed in human platelet rich plasma (2.5 x 10(8) platelets.ml(-1)) at a concentration of 1.35 mM. Arachidonic acid (AA), adenosine diphosphate (ADP), collagen (COL) and thrombin (TR) were used as agonists of platelet aggregation. All tested substances, except pralidoxime and methoxime, caused a significant inhibition of the aggregation process induced by AA, ADP and COL. Of the oximes assayed, none was found to influence TR triggered aggregation. Since reduced platelet aggregation can play an important role as an adverse effect in reactivator administration, further evaluation is needed for the estimation of the real impact of active oximes to the aggregation process in humans.     

Effect of buflomedil on epinephrine-enhanced platelet aggregation in vitro and ex vivo

The effect of buflomedil (4-(1-pyrrolidinyl)-1-(2,4,6-trimethoxyphenyl)-1-butanone) in vitro and ex vivo after intravenous and oral administration was tested upon epinephrine-enhanced platelet aggregation (PA) in platelet-rich plasma (PRP) prepared from heparinized blood of healthy volunteers. In vitro incubation of PRP with buflomedil in concentrations above 10 mumol/l resulted in a significant depression of PA to approximately one-third of the control. 30 min after a single intravenous dose of 2.5 mg/kg buflomedil a depression of epinephrine-enhanced PA to about 60% of the value before injection of the drug was observed. This effect wore off during a few hours and was no longer present 24 h thereafter. Oral ingestion of 600 mg/d buflomedil depressed PA to approximately two-thirds within 2 days, with a further decrease to some 50% after 6 days of intake. 2 days after termination of treatment epinephrine-enhanced PA had returned to premedication values. Unlike nonsteroidal antiinflammatory drugs buflomedil does not act through an inhibition of prostaglandin synthesis.     

Effect of fibrinopeptides A and B on human and rat platelet aggregation in vitro

The effect of fibrinopeptides on platelet aggregation is reported. Fibrinopeptide A (minimal effective concentration, 0.65 microM) aggregated human (but not rat) platelets suspended in plasma and at lower concentrations (0.01-0.1 microM) potentiated platelet aggregation due to ADP and collagen in both species. Fibrinogen mimicked these effects of fibrinopeptide A. P-bromophenacyl bromide (100 microM), mepacrine (10 microM), indomethacin (10 microM) and dazoxiben (10 microM) inhibited human platelet aggregation induced by fibrinopeptide A and fibrinogen. In both species, fibrinopeptide B (0.65-6.5 microM) antagonised the platelet inhibitory effect of PGI2 and PGD2 but not adenosine. Antagonism was non-competitive in nature. The concentration of fibrinopeptide A required to potentiate platelet aggregation occurs naturally in the plasma of patients with thrombotic disease suggesting this effect may be of physiological significance during the formation of a thrombus. The novel action of fibrinopeptide B to reduce the platelet inhibitory effect of PGI2 and PGD2 may also contribute to the control of thrombus formation.     

雷公藤内酯醇诱导兔血小板聚集作用

雷公藤内酯醇 (Ｔｒｉｐｔｏｌｉｄｅ ,Ｔｒｉ)具有抗肿瘤、免疫抑制、抗炎等生物活性 ;临床上用于治疗银屑病 ,类风湿性关节炎及白血病[1] 。但在动物实验和临床应用中发现其静脉注射会引起严重的血栓性浅静脉炎 ;为探讨其引起血栓性浅静脉炎的机制 ,我们观察了Ｔｒｉ对兔血小板功能的影响。1　材料与方法1.1　材料　Ｔｒｉ由本所提取 ,纯度 99 9% ,使用时以 2 %丙二醇配成所需浓度。ＡＤＰ美国Ｓｉｇｍａ生产 ;5 ＨＴ瑞士Ｆｌｕ ｋａ生产 ;ＴＸＢ2 放免药盒 ,中国医学科学院基础所提供 ;ｃＡＭＰ和ｃＧＭＰ放免药盒 ,中国原子能研究所提…     

苦豆碱对兔血小板聚集的影响

苦豆碱抑制低浓度花生四烯酸(AA)和胶原诱导的兔血小板聚集,IC_(50)分别为184μg·L~(-1)和38.3mg·L~(-1)提高AA浓度使其抑制作用明显减弱。苦豆碱还抑制兔血小板形成血栓素B_2(TXB_2),此作用可能和其对血小板聚集的抑制有关。     

Effect of RGD-containing peptides on platelet aggregation

The influence of new synthetic peptides ARGDS-NH2 and RGD-dFK (synthesized by the fermentative method) and VPNLRGDLQVLA (a fragment of the foot-and-mouth virus's surface peptide) on the ADP-induced human platelet aggregation in vitro was studied. All peptides were found to inhibit the human platelet aggregation, but the synthetic peptides (ARGDS-NH2 and RGD-dFK) showed the most pronounced effect. Significant decrease in the platelet aggregation was observed at their concentrations within 0.1-10 mM. ARGDS-NH2 and RGD-dFK inhibited the platelet aggregation stronger than the reference drug pentoxifylline at equivalent concentrations.     

木瓜蛋白酶体外对血小板聚集的抑制作用

目的：以洗涤血小板为模型,观察木瓜蛋白酶在体外对血小板聚集的抑制作用,以探讨其抗血栓作用的可能机制。方法：将不同剂量木瓜蛋白酶与洗涤血小板作用,以血小板聚集分析仪检测ADP、花生四烯酸（AA）、胶原和凝血酶诱导的血小板最大聚集率,以流式细胞仪检测活化血小板膜纤维蛋白原受体（FIB-R）和P-选择素表达水平,以SDS-PAGE分析血小板肌动蛋白聚合体的变化。检测ADP诱导的原发性高血压（PH）及急性心肌梗死（AMI）患者血小板最大聚集率和FIB-R表达水平。结果：木瓜蛋白酶剂量依赖性地抑制血小板聚集,降低血小板最大聚集水平,血小板聚集水平与木瓜蛋白酶剂量呈负相关（P〈0.01）。木瓜蛋白酶剂量依赖性地抑制ADP诱导的血小板FIB-R表达,降低FIB-R表达水平（P〈0.01）。木瓜蛋白酶降低ADP诱导的血小板膜P-选择素表达水平和抑制肌动蛋白聚合体增加（P〈0.01）。木瓜蛋白酶抑制PH及AMI患者血小板聚集和FIB-R表达（P〈0.01）。结论：木瓜蛋白酶通过抑制活化血小板膜纤维蛋白原受体的表达,并抑制肌动蛋白聚合以及释放反应从而剂量依赖性地抑制血小板的聚集反应,有抗血栓形成作用。     

Endothelium-derived relaxing factor inhibits in vitro platelet aggregation

We studied the effects of endothelium-derived relaxing factor (EDRF), bovine retractor penis muscle inhibitory factor and sodium nitroprusside, three stimulants of guanylate cyclase, on the in vitro aggregation of washed human platelets. Platelet aggregation induced either by collagen or by the thromboxane A2 analogue U46619 was inhibited by all three agents. The anti-aggregatory effect of each agent was inhibited by haemoglobin. The anti-aggregatory effect of EDRF was potentiated by superoxide dismutase. These findings are discussed in relation to a potential role for EDRF in haemostasis.     

Bradykinin-induced contraction of guinea pig lung in vitro

We have investigated the contractile effect of bradykinin (BK) in guinea pig lung in vitro. BK induces a dose-related contraction of lung parenchymal strips which is increased significantly in the presence of 10^–5 M captopril (an angiotensin converting enzyme inhibitor) or 10^–5 M dl-thiorphan (a neutral endopeptidase inhibitor). The kininase I inhibitor, dl-2-mercaptomethyl-3-guanidino-ethylthiopropionic acid (MGTPA), has no effect on the BK-induced contraction. BK is more potent in contracting parenchymal lung strips than other contractile agents (histamine, carbachol and substance P), however the BK-induced maximal contraction is lower than those obtained with histamine and carbachol. The B₁ agonist, des-Arg⁹-BK, does not contract lung parenchymal strips. The new BK B₂ receptor antagonists (Hoe 140, NPC 17731 and NPC 17761), which possess binding affinities in the nanomolar range, inhibit the BK-induced contractile response in a dose-dependent manner. The BK-induced contraction was unaffected by propranolol, atropine, tetrodotoxin, capsaicin pre-treatment, triprolidine, methysergide, Ro 19-3704 and N-nitro-l-arginine-methyl-ester (l-NAME), excluding the involvement of nervous pathways, preformed mast cell mediators, platelet-activating factor and nitric oxide. However, indomethacin, a cyclooxygenase inhibitor, AA-861, a 5-lipoxygenase inhibitor, and furegrelate, a thromboxane A₂ synthase inhibitor, decreased the contractile response to BK, suggesting that both cyclooxygenase and 5-lipoxygenase products are involved in this contraction. Thapsigargin, an inhibitor of the endoplasmic reticulum Ca²⁺ ATPase, abolished the BK-induced contraction demonstrating an intracellular calcium-dependent mechanism. Moreover, on a mixed lung cell suspension, obtained by enzymatic digestion, BK is able to induce phosphoinositide production. We conclude that BK, acting on B2 receptors, is a powerful contractile agent of the guinea pig lung in vitro. The BK-induced contraction, modulated by kininases II, is not dependent on neural mechanisms whereas both eicosanoids and intracellular calcium are involved. Correspondence to: J. P. Gies at the above address     

N-Hydroxylation of 2-aminofluorene in the guinea pig and by guinea pig liver microsomes in vitro

Summary N-hydroxy-2-aminofluorene was found in the urine of guinea pigs intraperitoneally injected with 2-aminofluorene. The hydroxylamine was oxidized to the nitroso analogue and this was identified and determined in the carbon tetrachloride extract by its characteristic UV absorption, by thin-layer chromatography, and by the formation of a diazo compound in the reaction with nitrous acid. Only a small fraction of the 2-aminofluorene injected appeared in the urine as N-hydroxy derivative.Guinea pig liver microsomes were observed to N-hydroxylate 2-aminofluorene rather rapidly, the reaction proceeding at least as rapidly as the N-hydroxylation of aniline.The results of this paper were presented at meetings of the Deutsche Pharmakologische Gesellschaft in Mainz, April 26 to 28, 1965 (Kampffmeyer and Kiese) and Göttingen, September 27 to 30, 1965 (von Jagow, Kiese, Renner, and Wiedemann).     

异钩藤碱体外对家兔血小板聚集和胞浆游离钙离子浓度的影响

目的研究异钩藤碱对血小板内游离钙离子浓度([Ca2+]i)的影响,以探讨其抗血小板聚集作用的可能机制。方法比浊法测定家兔血小板聚集功能;双波长Fura-2荧光法测定血小板胞浆[Ca2+]i。结果异钩藤碱0.33~1.30mmol.L-1体外给药对ADP和凝血酶引起的血小板聚集有浓度依赖性的抑制作用。存在细胞外钙时,异钩藤碱对基础状态血小板的[Ca2+]i和ADP及凝血酶诱导的[Ca2+]i水平有浓度依赖性的降低作用,而无细胞外钙存在时,则均无明显影响,表明其可抑制血小板的外钙内流,对内钙释放无明显抑制作用。结论异钩藤碱可抑制血小板聚集,其作用机制可能与其抑制血小板胞浆[Ca2+]升高有关。