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。     

Comparative inhibitory effects of dihydropyridines on platelet aggregation, calcium uptake and cyclic AMP concentration.

We studied the in vitro effects of several calcium channel blockers from the dihydropyridine (DHP) family on platelet aggregation and endogenous serotonin secretion, calcium uptake and cyclic AMP (cAMP) concentration using washed rat platelets. We found that, after 1 min incubation, nifedipine (Nif), nitrendipine (Nit) and nisoldipine (Nis) inhibited the thrombin-induced platelet aggregation and serotonin secretion with IC50 of about 140, 5 and 2 mumol/l, respectively. Nis and Nit are thus much more active than Nif. We also found that the thrombin-induced Ca2+ uptake amounted to 2,600 +/- 326 pmol Ca2+/10(9) platelets in control conditions. In the presence of 10 mumol/l of the DHP, this uptake was decreased by 19, 49 or 77%, with Nif, Nit or Nis, respectively. Compound BAY K 8644 (BK) with known agonistic properties on the calcium channel had inhibitory effects on the studied parameters. These compounds were in the order of Nif < BK < Nit < Nis. When added to previously aggregated platelets, Nit caused them to deaggregate. These results seem to be similar to those obtained with cAMP analogues or adenylate cyclase activators. The platelet resting cAMP concentration was therefore measured in the presence of the DHP. A nonsignificant increase was found with 20 mumol/l Nif whereas significant increases of 20 and 68% as compared with controls were obtained with 20 mumol/l Nit and Nis, respectively. Partition studies between platelets and plasma lipoproteins indicated that the effects might be related to the lipophilicity of the compounds. These data suggest that these agents work on platelet activity by multiple effects located intracellularly or at the membrane level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and inhibitory effects of 1,2,4-triazole derivatives on platelet aggregation.

Various derivatives of triazole substituted in the 2-position were prepared, and their activity on platelet aggregation tested. Compounds 4 and 14 had the most powerful action. These agents were thought to inhibit platelet aggregation via an inhibition of the cyclo-oxygenase-peroxidase complex (PGS complex), preventing synthesis of prostaglandins.     

国产依替巴肽抗犬血小板聚集作用研究

目的研究国产血小板糖蛋白Ⅱb/Ⅲa受体拮抗剂依替巴肽体内、体外抗犬血小板聚集作用及作用特点。方法采用比浊法测定血小板聚集,观察依替巴肽体外抗血小板聚集作用;模拟临床采取负荷量与维持量连续给药的方式,观察依替巴肽体内抗血小板聚集作用。结果依替巴肽体外抗犬血小板聚集的半数抑制浓度为136.7±72.6 nmol·L-1;体内给药可迅速抑制犬血小板聚集,在给药期间维持其抑制效应并呈现剂量依赖性;各剂量组血小板聚集抑制率均大于80%,达到临床血小板抑制靶目标。结论国产依替巴肽体内、体外可强效、快速、稳定地抑制犬血小板聚集。     

Studies on the inhibitory effect of etafenone hydrochloride on platelet aggregation

The inhibitory effect of etafenone hydrochloride (etafenone) on platelet aggregation in rabbit platelet rich plasma and the involvement of the arachidonic acid (AA) cascade in the inhibitory mechanism for etafenone on platelet aggregation were studied. 1) Etafenone exhibited a dose-dependent inhibitory effect on collagen (15--20 micrograms/ml)-induced platelet aggregation, and its median inhibitory concentration (IC50) was 1.7 X 10(-5)M. 2) In ADP (20 microM)-induced aggregation, etafenone also exhibited a dose-dependent inhibitory effect, but its IC50 was 2.7 X 10(-4)M and was significantly higher than that in the case of collagen. 3) Etafenone inhibited AA (0.3--0.5mM)-induced platelet aggregation dose-dependently. Its IC50 was 2.8 X 10(-5)M. 4) In thromboxane (TX) A2-induced aggregation, etafenone exhibited a dose-dependent inhibition, and the IC50 was 3.2 X 10(-4)M. 5) Trapidil which was reported to inhibit platelet aggregation via phosphodiesterase (PDE) inhibition had a similar IC50 on ADP- and TXA2-induced platelet aggregation to that of etafenone, but in collagen- and AA-induced aggregation, its IC50 was higher than that of etafenone. 6) Etafenone (3 X 10(-6)--3 X 10(-4)M) dose-dependently inhibited the production of TXB2 in PRP induced by collagen. 7) Etafenone scarcely affected TXA2 synthetase activity in rabbit platelet homogenate. 8) The correlation between the inhibitory effect of etafenone on platelet aggregation and inhibition of AA metabolism activation and PDE inhibition was discussed.     

Thromboxane synthetase inhibitors. I. Synthesis of some imidazolylarylmethanols and their inhibitory activity on platelet aggregation

Several imidazolylpyridinemethanols and imidazolylbenzenemethanols were prepared and evaluated for an inhibitory activity against arachidonic acid-induced platelet aggregation. The result shows that the arylmethanol moiety is essential for the activity and may correspond to the 15-OH group of prostagrandin H2 (PGH2). Among the compounds tested, 4-[alpha-hydroxy-5-(1-imidazolyl)-2-methylbenzyl]-3,5-dimethylbenzoic acid (XV) was found to have a potent inhibitory activity and a long duration of action. Structure-activity relationships are also discussed briefly.     

Pharmacokinetics and platelet aggregation inhibitory effects of a novel intravenous formulation of clopidogrel in humans

1. PM103 is an intravenous formulation of clopidogrel being developed as an alternative to oral clopidogrel to provide for dosing flexibility in the emergent clinical setting. The present first-in-human study assessed the pharmacokinetic and pharmacodynamic effects of PM103 and its safety in 144 healthy human subjects. 2. The present was a randomized open-label parallel-group trial. Single intravenous doses of PM103 (0.1, 1.0, 10, 30, 100 or 300 mg) were administered to each group (n = 24 subjects per group). Platelet aggregation was assessed at baseline and then 15 and 30 min and 2, 5 and 24 h after drug administration. Determination of plasma concentrations of clopidogrel, clopidogrel carboxylic acid metabolite and the clopidogrel thiol metabolite were assessed at baseline and at 1, 5, 10, 20 and 30 min and 1, 2, 3, 4, 6, 8, 12 and 24 h after drug administration. 3. PM103 produced a rapid, persistent and dose-related inhibition of platelet aggregation. The onset of the ant platelet effect paralleled the appearance in plasma of the clopidogrel thiol active metabolite. PM103 was well tolerated and no subjects discontinued treatment because of adverse events. 4. These data suggest that PM103 may be a suitable alternative to oral clopidogrel for patients in whom the desired clinical management would include administration of clopidogrel after coronary angiography but prior to percutaneous coronary intervention.     

Mineral fiber-induced leukocyte activation: the role of intra- and extracellular calcium

The role of intra- and extracellular calcium in the activation of human polymorphonuclear leukocytes (PMNL) to produce reactive oxygen metabolites (ROM) were studied by using soluble, formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate (PMA), or particulate stimuli, quartz or chrysotile. A calcium channel inhibitor, verapamil, attenuated only quartz-induced elevation of free intracellular calcium ([Ca²⁺]_i) and ROM production. Likewise, ethyleneglycol-bis (aminoethyl ether) tetraacetic acid (EGTA) attenuated quartz-, chrysotile- and fMLP-induced elevation of [Ca²⁺]_i; and ROM production. It also inhibited PMA-induced ROM production. A calcium ionophore, A23187 amplified ROM production by all of these stimuli. These results suggest that both intra- and extra-cellular calcium are required for the full activation of respiratory burst by soluble and particulate stimuli in human PMNL.     

川芎嗪芳酸醚甘氨酸衍生物合成及抗血小板聚集活性

目的 合成一系列新的甘氨酸衍生物,并初步筛选其抗血小板聚集活性.方法 以川芎嗪、甘氨酸、阿魏酸等芳酸为起始原料,经过一系列反应,合成得到目标化合物.结果 合成了6个川芎嗪芳酸醚类甘氨酸衍生物,其结构均经IR、1H-NMR、13C-NMR和MS确证.结论 所有目标化合物均未见文献报道.药理结果初步显示化合物1a、1b、1...     

The inhibitory effect of liposome-encapsulated indomethacin on inflammation and platelet aggregation

A comparison has been made between liposome-encapsulated and free indomethacin for their anti-inflammatory activities in the carrageenan paw oedema test in rats, and their inhibitory effect on platelet aggregation induced by adenosine 5-diphosphate (ADP) in-vitro. Free indomethacin, 3 mg kg-1, strongly inhibited carrageenan-induced oedema and a similar inhibitory activity was shown by 0.3 mg kg-1 of encapsulated drug. For the inhibition of platelet aggregation, the threshold concentration of free drug was 0.559 mM. At this concentration, at least 5 min incubation was needed to achieve 12.5% and 45 min for 50% inhibition. The inhibition was much stronger with encapsulated drug, and pre-incubation of 28 microM encapsulated drug for 10 min with platelet-rich plasma before addition of ADP completely inhibited platelet aggregation.     

吡考他胺类似物的合成及其抑制血小板聚集作用

目的为寻找新的抗血小板聚集剂,以抗血小板聚集药物吡考他胺(picotamide)为先导化合物,对其结构进行改造,合成新的类似物.方法以苯甲醚为原料,经3步反应制得中间体4-甲氧基-1,3-苯二甲酰氯,经与不同的胺类化合物进行取代反应制得目标化合物.结果与结论共制得10个新化合物,其结构经红外和核磁共振谱确证.药理实验结果表明,化合物PN9和PN10的抗血小板聚集活性很高,明显优于阳性对照药物picotamide.     

The mode for the manifestation of the inhibitory effects of ifenprodil tartrate on platelet aggregation in vivo and ex vivo

The mode for the manifestation of the inhibitory effect of ifenprodil tartrate on platelet aggregation in vivo and ex vivo was studied in mice and men, respectively. The ifenprodil level in plasma reached the maximum in 20 min after oral administration of 30 mg ifenprodil tartrate/kg in mice, and it decreased over a 3 hr period after the administration. On the other hand, the maximal inhibitory effect was observed 60 min after the administration. Thus ifenprodil tartrate manifested its inhibitory effect on platelet aggregation only after the maximum plasma concentration of ifenprodil was reached. The same phenomenon was observed with the inhibitory effects of ifenprodil tartrate on platelet aggregation ex vivo in man. To clarify the reason for the delay in the manifestation of the inhibitory effects of ifenprodil, the ifenprodil contents in mouse platelets after the oral administration of the drug was measured. The pattern of change in the ifenprodil contents in platelets was found to resemble closely the pattern of the change in its inhibitory effects, suggesting that the manifestation of the inhibitory effects on platelet aggregation by oral administration of ifenprodil tartrate was directly related to the ifenprodil contents in platelets rather than the ifenprodil level in plasma.     

Differences between negative inotropic and vasodilator effects of calcium antagonists acting on extra- and intracellular calcium movements in rat and guinea-pig cardiac preparations

Summary In order to get more insight into the utilization of calcium in the mammalian heart and the influence of calcium antagonists on this process we have evaluated the negative inotropic and vasodilator effect of nifedipine, diltiazem, verapamil, bepridil and lidoflazine as well as of the intracellularly acting calcium antagonists ryanodine and TMB-8 in the presence of 0.9 and 1.8 mmol/l calcium in rat Langendorff hearts. The effect of ryanodine was also studied in guinea-pig Langendorff hearts. In addition, in rat and guinea-pig papillary muscles the effect of these drugs on the force of contraction was examined.With the exception of ryanodine and TMB-8 all calcium antagonists induced a pronounced coronary vasodilator effect. The rank order of potency for this effect was: nifedipine > verapamil = diltiazem = bepridil = lidoflazine in the presence of 0.9 mmol/l calcium. At a calcium concentration of 1.8 mmol/l nifedipine and verapamil proved more potent, whereas diltiazem was less active. All calcium antagonists completely suppressed the development of the left ventricular pressure. At a calcium concentration of 0.9 mmol/l the potency order for this effect was: ryanodine > nifedipine = verapamil > diltiazem = bepridil = lidoflazine > TMB-8. In the presence of 1.8 mmol/l calcium the concentration-response curves for reduction of the left ventricular pressure by nifedipine, verapamil and diltiazem slightly shifted to the right. In contrast to all calcium antagonists investigated, in guinea-pig Langendorff hearts ryanodine only partially decreased the left ventricular pressure.In rat papillary muscles ryanodine nearly completely reduced the force of contraction, whereas nifedipine only partially inhibited the force of contraction. Lidoflazine only slightly affected the force of contraction. In guinea-pig papillary muscles all drugs partially decreased the force of contraction. Lidoflazine, however, was more effective than in rat papillary muscles. In rat and guinea-pig papillary muscles the force of contraction was fully suppressed by a combination of nifedipine and ryanodine.The results of the present study suggest that in the rat heart extracellular calcium plays a major role in the maintenance of the coronary vascular tone. The development of contractile force relies on the release of activator calcium from the sarcoplasmic reticulum but also requires the influx of calcium through dihydropyridine-sensitive channels. In the guinea-pig heart activator calcium may also be released from a source complementary to the sarcoplasmic reticulum. Lidoflazine displays certain selectivity towards this particular calcium pool.Preliminary results have been presented at the Spring Meeting of the German Pharmacological and Toxicological Society, 14–17 March, 1989, Mainz (Hugtenburg et al. 1989a)     

Comparison of the effects of isobutylmethylxanthine and milrinone on ischaemia-induced arrhythmias and platelet aggregation in anaesthetized rabbits.

1. The aim of this study was to compare the effects of the non-selective phosphodiesterase (PDE) inhibitor, isobutylmethylxanthine (IBMX) and the selective PDE III inhibitor, milrinone, in a rabbit model of acute myocardial ischaemia. 2. Coronary artery occlusion caused changes in the ST-segment of the ECG and ectopic activity in all control rabbits. Ventricular fibrillation occurred in 10 out of 14 (71%) of these animals. Pretreatment with IBMX 100 micrograms kg-1 plus 10 micrograms kg-1 min-1, starting 10 min before coronary artery occlusion, reduced ischaemia-induced ST-segment changes and ventricular fibrillation occurred in only 10% of this group (n = 10). A similar dose of milrinone had no antiarrhythmic activity, whereas with a lower dose of milrinone, 30 micrograms kg-1 plus 3 micrograms kg-1 min-1 (n = 10), only 30% of rabbits fibrillated and ST-segment changes were attenuated. 3. Acute administration of both IBMX and milrinone reduced arterial blood pressure. With the higher dose of milrinone a significant effect was still present after 10 min of drug infusion. A greater hypotensive response to the higher dose of milrinone was observed in the rabbits which subsequently fibrillated during ischaemia. A marked tachycardia was also observed after administration of the higher dose of milrinone. 4. At the end of the experiment platelet aggregation was studied ex vivo. ADP-induced aggregation was reduced by pretreatment of the rabbits with milrinone but not IBMX. Both PDE inhibitors enhanced the ability of isoprenaline to inhibit ADP-induced platelet aggregation but milrinone was more effective, particularly at the higher dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Paradoxical effect of calcium on some cardiovascular effects of verapamil in the rat

The ability of calcium infusions to reverse some cardiovascular effects of verapamil was tested in anesthetized rats and on isolated rat atria. Intravenous infusions of 1.88 mg/kg verapamil increased the cycle length (CL), lengthened the PR interval (PRi), and decreased the mean arterial pressure (Pa). After these effects were stabilized, a series of infusions of calcium chloride (338 mumol/kg each) were performed. Calcium on the one hand promoted the return of Pa to its basal value; on the other hand, it failed to reverse the effect of verapamil on AV conduction and the first infusion of calcium produced an additional increase in CL of 55 +/- 16 ms. This paradoxical effect of calcium was prevented by previous infusion of atropine (0.2 mg/kg). On isolated atria, the increase of calcium concentration in the media ([Ca2+]0) from 1.0 to 6.0 mM increased the concentration frequency by approximately 40 beats/min, both in atropinized and in nonatropinized preparations. After verapamil, however, the same increase in [Ca2+]0 decreased atrial rate in 50 +/- 15 beats/min in nonatropinized atria. The results obtained indicate that extra calcium can overcome the hypotensive effect of verapamil, whereas it paradoxically increases its negative chronotropic effect and fails to reverse its effect on AV conduction. This paradoxical effect of calcium can be prevented, both in vivo and in vitro, by atropine blockade of muscarinic receptors.     

阿魏酸衍生物的合成及抗血小板聚集活性

以具有活血化瘀作用的中药有效成分阿魏酸为先导物,设计合成了6个阿魏酸衍生物,其结构经IR、1H NMR、13C NMR及MS确证。体内药效筛选结果显示,阿魏酸衍生物对二磷酸腺苷(ADP)诱导的血小板聚集具有较好的抑制活性,其抑制作用明显强于阳性对照药奥扎格雷钠。     

Influence of ethanol and serotonin on rat platelet aggregation

We demonstrated that ethanol (1.0, 2.0 and 4.0 g/kg p.o.) significantly decreased blood platelet aggregation in a dose-dependent manner. The chronic administration of ethanol (6 g/kg daily for 4 weeks) also altered the sensitivity of rat platelets to ADP (4 mumol/l). We found that the acute and chronic administration of alcohol significantly increased the amplifying effect of 5-hydroxytryptamine (5-HT; 10(-6) mol/l) on ADP-induced aggregation. In all groups of rats, ketanserin (10(-5) mol/l) completely inhibited the amplification of aggregation induced by serotonin. In conclusion, the present results show that ethanol did not only produce inhibition of ADP-induced platelet aggregation but also affected the potentiating action of 5-HT on this process.     

Amidinosemicarbazido derivatives of pyrazole: synthesis and inhibitory effect on blood coagulation and platelet aggregation

Amidinosemicarbazido derivatives of pyrazole having various substituents on pyrazole ring were prepared and their effect on platelet function and blood coagulation was determined in vitro. Platelet aggregation and serotonin release induced by ADP, collagen, arachidonic acid and thrombin were markedly inhibited by pyrazole derivatives at mM concentrations. Compounds with a hydrophobic nucleus at position 1 of the pyrazole ring showed the most potent antiplatelet activity. On the contrary, their effect on blood coagulation was faintly inhibitory.     

Amlodipine in hypertension: its effects on platelet aggregation and dynamic exercise

The antihypertensive efficacy and safety of once-daily amlodipine (5-10 mg) were studied in patients with essential hypertension. The study also included an assessment of the effects of single doses of amlodipine on platelet aggregation. Ten patients received amlodipine (mean daily dose of 7 mg) for 12 weeks in an open chronic study preceded by a 4-week placebo run-in period. Amlodipine significantly reduced the mean dorsal supine (-31/-20 mm Hg), sitting (-34/-23 mm Hg), standing (-34/ -23 mm Hg), and postexercise (-30/-20 mm Hg) blood pressures (BPs) at the end of 12 weeks of treatment compared with the placebo run-in period (p < 0.005), with no significant change in heart rate. At the end of a 4-week placebo washout phase following the chronic study, nine of the patients received an acute single 10-mg dose of amlodipine. Exercise testing before and 6 h after dosing showed that an acute 10 mg dose of amlodipine reduced BP without modifying the physiologic response to dynamic exercise. Amlodipine significantly reduced the degree of platelet aggregation in these patients (p < 0.005) induced by either collagen or ADP. This study demonstrated that amlodipine once daily was an effective antihypertensive agent and significantly inhibited platelet aggregation.