Anticoagulant and lipolytic effects of a low molecular weight heparin fraction

The lipolytic and anticoagulant actions of a 4000 dalton low molecular weight (LMW) heparin were compared with unfractionated mucosal heparin after intravenous and various subcutaneous doses in man. I.v. injection of 100 USP units/kg body weight lipoprotein lipase (LPL) activity, and inhibition of factor Xa decreased with a half life twice as long after LMW heparin compared to normal heparin (p < 0.05). There were no differences in half lives for HTGL activity, thrombin inhibition and on aPTT. The area under the activity time curve (AUC) of LPL and factor Xa was double with LMW heparin (p < 0.05). S.c. administration showed that the AUC of LMW heparin on the factor Xa inhibition was 10 times larger compared to normal heparin. LPL activity was released comparable to normal heparin. The effects on HTGL were three times larger compared to normal heparin. There were no differences in half lives. The data show that in contrast to normal heparin LMW heparin is rapidly and completely absorbed from the subcutaneous depots. The pharmacodynamic data of LPL activity and factor Xa inhibition suggest similar release mechanisms.     

低分子肝素对进展性缺血性脑卒中预防作用的探讨

目的 探讨低分子肝素对进展性缺血性脑卒中的预防作用。方法 将起病在72小时内的203例脑梗死患者随机分成低分子肝素治疗组及常规治疗组。低分子肝素组在常规治疗的基础上加用低分子肝素0．4ml,每日2次腹部皮下注射,连续5－10天。治疗前后检测纤溶酶原和凝血因子X活性及血液流变学各项指标,同时对进展性缺血性脑卒中患者的神经功能缺损进行评分。结果 低分子肝素组11例发生进展性缺血性脑卒中,常规治疗组23例,两组比较有显著性差异（P＜0．05）;低分子肝素组发生的进展性卒中其进展的严重程度比常规治疗组轻（P＜0．01）;近期预后较常规治疗组好（P＜0．05）;低分子肝素治疗能明显降低纤溶酶原和凝血因子X活性及血液流变学各项指标。结论 低分子肝素治疗能降低进展性缺血性脑卒中发生率,有利于进展性缺血性脑卒中患者神经功能的恢复。     

The effects of heparin and low molecular weight heparins on bone

Recent clinical trials have shown that the risk of developing osteoporosis is substantially lower when low molecular weight heparins (LMWHs) are used in place of unfractionated heparin. While the reason(s) for this difference has not been fully elucidated, studies with animals have suggested that heparin causes bone loss by both decreasing bone formation and increasing bone resorption. In contrast, LMWHs appear to cause less bone loss because they only decrease bone formation. Whether all LMWHs decrease bone formation and therefore cause bone loss is unknown. For example, preliminary in vitro studies with the synthetic pentasaccaride, Fondaparinux, have suggested that it may not decrease bone formation and thus, may have no deleterious effects on bone. Further studies are required in order to determine if all LMWHs cause bone loss equally.     

低分子肝素对大鼠大脑皮层神经细胞缺血再灌注损伤的保护作用

目的研究低分子肝素(low molecular weight heparin,LMWH)对大鼠大脑皮层神经细胞缺血再灌注损伤的保护作用及其可能机制。方法体外培养新生大鼠大脑皮层神经细胞,建立缺血再灌注模型,MTT法检测细胞活力,Annexin V-FITC、PI双染流式测细胞凋亡率,荧光分光光度计法测定细胞内钙离子浓度。结果低分子肝素可提高缺血再灌注损伤的神经细胞活力,降低细胞凋亡率和细胞内钙离子浓度。结论低分子肝素对缺血再灌注损伤的大鼠大脑皮层神经细胞有保护作用,其机制可能与LMWH降低细胞内钙离子浓度有关。     

A low molecular weight heparin compared with unfractionated heparin

A 6000 daltons low molecular weight heparin (LMWH) was compared with unfractionated mucosal heparin in vitro and in vivo. Despite unimpressive specifications by clotting assays in vitro, the LMWH gave high and sustained activity in vivo by anti-Factor Xa assays, following subcutaneous injection. However, activity measured by APTT and calcium thrombin time assays was at least as high as occurred following unfractionated heparin. On the basis of clotting assays, there seems no reason to expect a lower incidence of haemorrhagic side-effects following the clinical use of this LMWH. The study also strikingly demonstrates the inadequacy of in vitro clotting assays for assessing the in vivo behaviour of LMWH.     

Comparative effects of heparin and PK 10169, a low molecular weight fraction, in a canine model of arterial thrombosis

The comparative properties of heparin and PK 10169, a low molecular weight fraction, were studied using an antithrombotic test in anaesthetized dogs. The antithrombotic properties of the two compounds were evaluated by measuring inhibition of thrombus formation following transluminar stimulation of coronary artery with anodal current and by measuring anticoagulant properties, anti Xa and anti IIa activities. The results show that PK 10169 displayed significant antithrombotic activities above 0.625 mg/kg and was equipotent at 2.5 mg/kg s.c. with heparin 10 mg/kg s.c. No correlation could be observed between antithrombotic/anti Xa ratio of both compounds. Moreover it was shown that, unlike heparin, PK 10169 s.c. was devoid of obvious anticoagulant properties and induced a negligible anti IIa activity contrasting with a high anti Xa level. A similar dissociation between anti Xa and anti IIa activities was observed following i.v. administration of 2.5 mg/kg of PK 10169 but not with heparin. This low molecular weight heparin fraction might thus be regarded as a potential arterial antithrombotic agent devoid of appreciable anticoagulant effect.     

低分子肝素钙治疗急性脑梗死的疗效观察

目的观察低分子肝素钙（LMWHCa）治疗急性脑梗死的疗效和安全性。方法选用48例急性脑梗死病人,其中24例用常规治疗为对照组,治疗组24例除常规治疗外,加用LMWHCa4100抗Xa国际单位腹部皮下注射,bid,连续10d为1疗程。治疗前后分别作神经功能评分、血液流变学观察和PT、AFTT、TT、Fg。结果治疗组神经功能恢复、血液流变学改善均明显优于对照组（P〈0．05）。治疗组用药后Fg降低,PT延长,与对照组比较差异显著（P〈0．01或P〈0．05）,两组治疗前后的TT、APTI变化不明显;治疗组有2例出现皮下淤斑。结论脑梗死急性期给予低分子肝素钙治疗安全和有效。     

Signs of thrombin generation in pediatric cardiac catheterization with unfractionated heparin bolus or subcutaneous low molecular weight heparin for antithrombotic cover

Introduction: Thrombosis is one of the most frequent adverse events after cardiac catheterization, which can be reduced by anticoagulation with unfractionated heparin (UFH) in both children and adults. Low molecular weight heparin (LMWH) might possibly offer advantages. Laboratory signs of thrombin generation during pediatric cardiac catheterization, with unfractionated heparin (UFH) bolus or subcutaneous LMWH for thrombosis prophylaxis, were determined in a first step to investigate the potential of LMWH for antithrombotic cover. Materials and methods: Signs of thrombin generation (D-dimer and F₁₊₂), anti-Xa activity and activated clotting time (ACT) were measured in 65 patients with congenital heart disease. A total of 40 patients were treated with a UFH bolus of 100 IU/kg bodyweight and, in 25 children, enoxaparin was subcutaneously administered at a dosage of 1/1.6 mg/kg bodyweight. Results: The dose to plasma activity of enoxaparin was more consistent than in the UFH group. Only a slight elevation of F₁₊₂ was found in some patients, which was a little higher in the enoxaparin group, but no difference of incidence of increased F₁₊₂ generation was detected between the two groups. D-dimer was elevated in three children after UFH bolus application, but no such effect was observed in any child after LMWH administration. Conclusions: Application of LMWH was equally efficacious during pediatric cardiac catheterization than UFH bolus administration, as determined by plasma levels and markers of clotting activation. In contrast to UFH bolus, no further monitoring was necessary after the application of LMWH during cardiac catheterization due to a consistent dose to plasma activity.     

The effect of low molecular weight heparin on experimental thrombosis and haemostasis--the influence of production method

Three low molecular weight heparins prepared by enzymatic depolymerization, chemical degradation, and fractionation, respectively were studied in experimental thrombosis and haemostasis models in vivo and in biological assays in vitro. The three low molecular weight heparins, which had comparable molecular weight distributions, showed very similar activities both in vitro and in vivo. All three showed dose dependent thromboprophylactic effect. The antithrombotic effects of the low molecular weight heparins and conventional heparin administered in the same dose (30 XaI u/kg b.w.) did not differ. Neither LMW heparin nor conventional heparin (60 or 90 XaI u/kg b.w.) showed significant effects on the haemostatic plug formation time in the rabbit mesenteric microcirculation.

These experiments confirm that low molecular weight heparins are potential antithrombotic drugs, which by intravenous administration have effects similar to those of standard heparin. The method of preparation seems to be of no or minor importance, at least if the molecular weight distributions of the products are similar.     

The disappearance of a low molecular weight heparin fraction (CY 216) differs from standard heparin in rabbits

In previous studies, we have reported that standard heparin (SH) was cleared by two mechanisms, a saturable mechanism which predominated at low doses (<100 anti-factor Xa U/kg) and a non-saturable mechanism which predominated at higher doses, when the first mechanism became saturated. In this study, we examined the importance of these two mechanisms in the disappearance of a low molecular weight heparin fraction (LMWH) (CY 216), by comparing the pharmacokinetics and the pharmacodyna-mics of a wide range of doses of SH and CY 216 (1.5 to 500 anti-factor Xa U/kg) Pharmacokinetics was measured as the disappearance of ¹²⁵I-radiolabelled SH or CY 216. Pharmacodynamics was measured as the disappearance of the anti-factor Xa activity of SH and CY 216. We found that the saturable mechanism contributed little to the disappearance of CY 216 and that it was cleared predominantly by the non-saturable mechanism at all doses tested. Thus, at low doses (<100 anti-factor Xa U/kg), SH was cleared more rapidly than CY 216, whereas at higher doses, CY 216 was cleared more rapidly than SH. We conclude that the mechanism of disappearance of LMWH's differ significantly from those of SH, and that this difference may explain the apparent prolonged anticoagulant activity of LMWH's within the therapeutic range doses.     

Comparative study of antithrombotic effect of a low molecular weight heparin and unfractionated heparin in an ex vivo model of deep arterial injury

Thrombosis after plaque rupture triggers the onset of acute coronary events. The treatment of choice for patients with acute coronary syndromes is conventional unfractionated heparin. Low molecular weight heparin has recently been reported to be as effective and even safer than unfractionated heparin. In this study, the effects of the low molecular weight heparin reviparin and unfractionated heparin on thrombus formation were examined under dynamic conditions using an extracorporeal perfusion chamber in a porcine model. Thrombus formation was assessed by the deposition of porcine ¹²³I-fibrin(ogen) and autologous ¹¹¹In-platelets on porcine tunica media at high and low shear rates. Reviparin reduced the fibrinogen molecules deposited on injured vessels at high shear rates (252±80 molecules×10¹²/cm² for reviparine (200 U/kg/hour) vs. 624±70×10¹²/cm² for unfractionated heparin (200 U/kg/hour) (p<0.05). At low shear rates, fibrinogen deposition was also significantly reduced by reviparin (130±15 molecules×10¹²/cm²) compared to unfractionated heparin (192±40×10¹²/cm² at 200 U/kg/hour; p<0.05). No change in platelet deposition was detected after heparin administration in either treatment group. In conclusion, the low molecular weight heparin reviparin has a higher antithrombotic potential than unfractionated heparin. Reviparin may have advantages over unfractionated heparin in treatment and prevention of acute coronary syndromes.     

急性脑血管病患者血浆低分子量肝素浓度监测

目的 研究脑血管病患者急性期（10d内）及亚急性期（4周内）血浆低分子量肝素（LMWH）浓度,了解LMWH样物质水平的自然变化趋势,并观察LMMH治疗干预后体内LMWH血浓度的变化以及出血副反应与浓度之间的关系。方法 应用发色底物法抗FXa测定法对84例急性脑血管病患者的血浆LMWH浓度进行动态观察。结果 脑梗死患者与脑出血患者血浆LMWH浓度在0.3-0.4之间,相比无显著性差异。应用LMWH治疗的脑梗死患者血浆LMWH浓度高于非治疗组,且有显著差异性。血浆LMWH浓度与出血副反应有一定的相关性。结论 监测血浆LMWH浓度有益于防止出血副反应,为个体化给药提供了基础。     

Sulfated low molecular weight lignins,allosteric inhibitors of coagulation proteinases via the heparin binding site,significantly alter the active site of thrombin and factor xa compared to heparin

Sulfated low molecular weight lignins (LMWLs) have been found to bind in the heparin binding sites of coagulation proteinases. LMWLs represent a library of diverse non-carbohydrate, aromatic molecules which are structures different from heparin, but still potently inhibit thrombin and factor Xa. To better understand their mechanism of action, we studied the effects of three sulfated LMWLs (CDSO3, FDSO3, and SDSO3) on the active sites of thrombin and factor Xa. LMWLs were found to uniformly inhibit the catalytic activity of thrombin and factor Xa, regardless of the substrate used. Michaelis-Menten kinetic studies indicate that maximal velocity of hydrolysis of each chromogenic substrate decreases significantly in the presence of sulfated LMWLs, while the effect on Michaelis constant is dependent on the nature of the substrate. These studies indicate that LMWLs inhibit thrombin and factor Xa through allosteric disruption of the catalytic apparatus, specifically through the catalytic step. As opposed to heparin, LMWLs significantly alter the binding of the active site fluorescent ligand p-aminobenzamidine. LMWLs also had a greater effect on the molecular orientation of fluorescein-labeled His 57 than heparin. The molecular geometry surrounding the most important catalytic amino acid, Ser 195, was significantly altered by the binding of LMWLs while heparin had no measurable effect on Ser 195. These results further advance the concept of sulfated LMWLs as heparin mimics and will aid the design of anticoagulants based on their novel scaffold.     

低分子肝素联合丹参注射液治疗急性脑梗死的效果分析

目的探讨低分子肝素和丹参注射液联合治疗急性脑梗死的临床效果。方法选取2012-12—2015-01我院诊治的急性脑梗死患者95例,随机分为研究组(n=48例)和对照组(n=47例),对照组实施基础治疗与丹参注射液,观察组加用低分子肝素治疗。比较2组治疗前后血液流变情况、神经功能改变情况(NIHSS评分),并评定临床疗效、并发症情况。结果2组治疗后血液流变学指标(纤维蛋白原、红细胞比积、血浆黏度、全血低切黏度、全血高切黏度)均明显低于治疗前(P0.05),且研究组较对照组降低更明显(P0.05);治疗后7、14、28d2组NIHSS评分均较治疗前明显降低(P0.05),且研究组各时点NIHSS评分较对照组更低(P0.05);研究组与对照组总有效率分别为91.67%和74.47%,研究组高于对照组(P0.05);2组并发症发生情况无明显差异(P0.05)。结论低分子肝素联合丹参注射液治疗急性脑梗死,患者脑部循环明显改善,效果显著,值得推广。     

A comparison of the anti thrombotic and haemorrhagic effects of low molecular weight heparin fractions: The influence of the method of preparation

Bleeding is an important complication of heparin therapy. A number of low molecular weight heparin fractions produce less bleeding than standard heparin for an equivalent antithrombotic effect in experimental animals. Low molecular weight heparin fractions and fragments are produced by a number of different procedures but their relative effects on haemostasis and thrombosis have not been evaluated. We have compared the antithrombotic and haemorrhagic effects of two low molecular weight heparin fragments and of a heparinoid with porcine mucosa heparin and related these in vivo findings to the results of ex vivo tests of blood coagulation and in vitro tests of platelet function. Haemorrhage was assessed using a rabbit ear bleeding model. The antithrombotic effects were assessed by measuring inhibition of a tissue thromboplastin-induced jugular vein thrombus and by inhibition of fibrin and platelet accumulation in an arterial-venous shunt. The ex vivo anticoagulant effects were     

Inhibition of low molecular weight heparin by protamine chloride in vivo

To determine the antagonization of anticoagulant and lipolytic effects of a low molecular weight [LMW] heparin preparation protamine chloride was given intravenously after i.v. injection of LMW or normal heparin. The effects of normal heparin on factor Xa, thrombin, aPTT, lipoprotein [LPL] and hepatic triglyceride lipase [HTGL] activities were neutralized immediately by i.v. protamine. The inhibition of thrombin and aPTT by LMW heparin were also abolished, whereas the effects on LPL and HTGL were counteracted to 80% and on factor Xa only to 40% by i.v. protamine chloride. No rebound of the anticoagulant or lipolytic effect was detected. It is assumed that haemorrhagic complication during therapy can be antagonized by protamine chloride. The incomplete inhibitory effect of protamine chloride on LPL, HTGL and factor Xa activities of LMW heparin indicate that protamine chloride requires more than 14 saccharide units in the heparin molecule for interaction.     

阿司匹林与低分子肝素钠联合治疗进展性脑梗死的临床疗效

目的探讨阿司匹林与低分子肝素钠联合治疗进展性脑梗死的临床疗效。方法收集2012-10—2014-08我院就诊的155例进展性脑梗死患者,随机分为对照组77例,研究组78例,对照组口服阿司匹林肠溶片治疗,研究组采用阿司匹林肠溶片及低分子肝素钠联合治疗,比较2组临床疗效、NIHSS评分、ADL评分。结果研究组总有效率89.74%,对照组75.32%,2组疗效差异有统计学意义(P0.05)。治疗后2组NIHSS评分明显降低,ADL评分明显升高,研究组治疗后NIHSS评分较对照组明显较低,ADL评分明显较高,差异有统计学意义(P0.05)。研究组治疗后PLT、Fg较治疗前及对照组治疗后显著降低,PT、APTT明显延长,差异有统计学意义(P0.05)。且2组均未见不良反应。结论阿司匹林与低分子肝素钠联合治疗进展性脑梗死临床疗效好,可改善患者NIHSS评分及ADL评分,可以在临床推广应用。     

低分子肝素对TIA患者黏附分子及血小板指标的影响

目的观察低分子肝素对短暂性脑缺血发作(TIA)患者黏附分子及血小板指标的影响。方法选取本院收治的68例(TIA)患者为研究对象,按照随机分配的原则分为对照组和观察组各34例,对照组进行常规治疗,观察组在对照组基础上加用低分子肝素,比较2组治疗前后的血清黏附分子及血小板指标。结果治疗前2组血清黏附分子及血小板指标比较,差异无统计学意义(P0.05),而治疗后2d、5d及7d观察组PLT均高于对照组,其他血清黏附分子及血小板指标均低于对照组,差异有统计学意义(P0.05)。结论低分子肝素可显著改善短暂性脑缺血发作患者的黏附分子及血小板指标。     

Prevention of experimental venous thrombosis in rabbits with low molecular weight heparin, dextran and their combinations, administered before or during induction of venous endothelial trauma

An in vivo experimental venous thrombosis model based on endothelial damage and flow reduction was used to investigate the effect of low molecular weight heparin (LMWH) alone and in combination with dextran and the effect of surgical and endothelial trauma on thrombus formation, formation of occlusive thrombi and thrombus weights. Five groups with 15 rabbits in each were studied. Two groups received dalteparin (50 anti-Xa IU/kg i.v.) before surgical trauma or after, during the endothelial trauma and two groups received dalteparin (50 anti-Xa IU/kg i.v.) with dextran 70 (1 g/kg i.v.) before surgical trauma or after, during the endothelial trauma. Compared to a control group (saline) all treatment regimes reduced significantly the frequency of thrombosis and occlusive thrombi as well as thrombus weights. No significant difference was observed between the identical treatment groups when the substances were introduced before respective after surgical trauma. It is concluded from the present study that thromboprophylaxis with LMWH in this particular in vivo model, given before or after surgical trauma is equally effective. Dextran has a certain augmenting thromboprophylactic effect when added to LMWH in this model.