[Determination of the anticoagulant activity of low molecular weight heparins by micellar electrokinetic chromatography combined with on-column enzymatic reaction]

Low molecular weight heparins (LMWHs) have largely replaced heparin for the treatment and prevention of thrombosis because of their various advantages over unfractionated heparins (UFHs) such as less bleeding, greater bioavailability, and more predictable anticoagulant effects. For special groups of patients, such as pregnant women, children, and patients with renal failure, it is necessary to monitor the anticoagulant activity of LMWHs in the blood. The traditional method used to determine the anticoagulant activity of heparin is the coagulation test. However, the results are various from different laboratories and different reagents. In contrast, the chromogenic substrate method is more accurate, sensitive and is easy to automate. Here, a method for the determination of the anticoagulant activity of LMWHs was developed by using a capillary-electrophoresis-based substrate chromogenic method. In this method, micellar electrokinetic chromatography (MEKC) was used in combination with electrophoretically mediated microanalysis to determine the anti-factor Xa (FXa) activity of LMWHs. The inhibition was measured by employing a chromogenic peptide substrate (CPS) with a p-nitroaniline (p-NA) moiety as the chromophore. The injection end of the capillary was used as a microreactor in which solutions of LMWHs, antithrombin Ⅲ (ATⅢ), FXa and CPS were successively injected and mixed by using diffusion, the transverse diffusion of laminar flow profiles and applied voltage. The reaction product p-NA was separated from unreacted CPS and sample matrix by using the MEKC mode with discontinuous background electrolyte system. The produced p-NA was baseline separated from the other components and detected at 380 nm to obtain maximum sensitivity. The amount of p-NA was inversely proportional to the activity of LMWHs in the sample. To improve the accuracy of quantification and the method repeatability of methods, nitrofurantoin (NF) was selected as the internal standard, which was added to the solution of CPS. The method was validated and used to measure a set of samples. The method is characterized by automation, good repeatability, high sensitivity, and cost-effectiveness. Additionally, the method does not interfere by the sample matrix, and thus can be used to monitor the anticoagulant activity of LMWHs in plasma.

Development of hydrophilic interaction chromatography with quadruple time-of-flight mass spectrometry for heparin and low molecular weight heparin disaccharide analysis

RATIONALE

Heparin and low molecular weight heparin (LMWH) are widely used as clinical anticoagulants. The determination of their composition and structural heterogeneity still challenges analysts.

METHODS

Disaccharide compositional analysis, utilizing heparinase-catalyzed depolymerization, is one of the most important ways to evaluate the sequence, structural composition and quality of heparin and LMWH. Hydrophilic interaction chromatography coupled with quadruple time-of-flight mass spectrometry (HILIC/QTOFMS) has been developed to analyze the resulting digestion products.

RESULTS

HILIC shows good resolution and excellent MS compatibility. Digestion products of heparin and LMWHs afforded up to 16 compounds that were separated using HILIC and analyzed semi-quantitatively. These included eight common disaccharides, two disaccharides derived from chain termini, three 3-O-sulfo-group-containing tetrasaccharides, along with three linkage region tetrasaccharides and their derivatives. Structures of these digestion products were confirmed by mass spectral analysis. The disaccharide compositions of a heparin, two batches of the LMWH, enoxaparin, and two batches of the LMWH, nadroparin, were compared. In addition to identifying disaccharides, 3-O-sulfo-group-containing tetrasaccharides, linkage region tetrasaccharides were observed having slightly different compositions and contents in these heparin products suggesting that they had been prepared using different starting materials or production processes.

CONCLUSIONS

Thus, compositional analysis using HILIC/QTOFMS offers a unique insight into different heparin products.

Collaborative study for the calibration of replacement batches for the heparin low-molecular-mass for assay biological reference preparation

The European Pharmacopoeia (Ph. Eur.) prescribes the control of the activity of low molecular mass heparins by assays for anti-Xa and anti-IIa activities (monograph 0828), using a reference standard calibrated in International Units (IU). An international collaborative study coded BSP133 was launched in the framework of the Biological Standardisation Programme (BSP) run under the aegis of the Council of Europe and the European Commission to calibrate replacement batches for the dwindling stocks of the Heparin low-molecular-mass for assay Biological Reference Preparation (BRP) batch 8. Thirteen official medicines control and manufacturers laboratories from European and non-European countries took part in this study to calibrate two freeze-dried candidate batches against the 3rd International Standard (IS) for heparin, low molecular weight (11/176; 3rd IS). The Heparin low-molecular-mass for assay BRP (batch 8) was also included in the test panel to check the continuity between subsequent BRP batches. Taking into account the stability data, the results of this collaborative study and on the basis of the central statistical analysis performed at the European Directorate for the Quality of Medicines & HealthCare (EDQM), the 2 candidate batches were officially adopted by the Commission of the European Pharmacopoeia as Heparin low-molecular-mass for assay BRP batches 9 and 10 with assigned anti-Xa activities of 102 and 100 IU/vial and anti-IIa activities of 34 and 33 IU/vial respectively.

Analysis of 3-O-sulfo group-containing heparin tetrasaccharides in heparin by liquid chromatography-mass spectrometry

Complete heparin digestion with heparin lyase 2 affords a mixture of disaccharides and resistant tetrasaccharides with 3-O-sulfo group-containing glucosamine residues at their reducing ends. Quantitative online liquid chromatography-mass spectrometric analysis of these resistant tetrasaccharides is described in this article. The disaccharide and tetrasaccharide compositions of seven porcine intestinal heparins and five low-molecular-weight heparins were analyzed by this method. These resistant tetrasaccharides account for from 5.3 to 7.3wt% of heparin and from 6.2 to 8.3wt% of low-molecular-weight heparin. Because these tetrasaccharides are derived from heparin's antithrombin III-binding sites, we examined whether this method could be applied to estimate the anticoagulant activity of heparin. The content of 3-O-sulfo group-containing tetrasaccharides in a heparin correlated positively (r=0.8294) to heparin's anticoagulant activity.

Diagnostic approach to pulmonary embolism in a rural emergency department

INTRODUCTION

Pulmonary embolism (PE) is a serious condition with mortality estimates of up to 10%. We sought to investigate the diagnosis of PE, time to access imaging and diagnostic utility of each modality in a rural emergency department (Ed).

METHODS

We completed a retrospective chart review to determine the investigations performed and treatments initiated in the management of suspected PE in a rural hospital.

RESULTS

A total of 47 charts from a 5-year period were reviewed. Of these, 83.0% indicated a D-dimer test was ordered, and 31.9% and 40.4% indicated either ventilation-perfusion (V/Q) or computed tomography (CT) were ordered during the ED visit. Computed tomography diagnosed 11 of the 12 instances of confirmed PE. Mean time to patients undergoing V/Q or CT was 1.58 and 1.59 days, respectively. Low-molecular-weight heparin was started in 83.0% of patients.

CONCLUSION

In this ED there may be over reliance on the D-dimer test, irrespective of Wells score. Access to V/Q and CT were similar to that of an urban centre. Empiric anticoagulation was started in most patients.

Chitosan-genipin microspheres for the controlled release of drugs: clarithromycin, tramadol and heparin

The aim of this study was to first evaluate whether the chitosan hydrochloride-genipin crosslinking reaction is influenced by factors such as time, and polymer/genipin concentration, and second, to develop crosslinked drug loaded microspheres to improve the control over drug release. Once the crosslinking process was characterized as a function of the factors mentioned above, drug loaded hydrochloride chitosan microspheres with different degrees of crosslinking were obtained. Microspheres were characterized in terms of size, morphology, drug content, surface charge and capacity to control in vitro drug release. Clarithromycin, tramadol hydrochloride, and low molecular weight heparin (LMWH) were used as model drugs. The obtained particles were spherical, positively charged, with a diameter of 1-10 microm. X-Ray diffraction showed that there was an interaction of genipin and each drug with chitosan in the microspheres. In relation to the release profiles, a higher degree of crosslinking led to more control of drug release in the case of clarithromycin and tramadol. For these drugs, optimal release profiles were obtained for microspheres crosslinked with 1 mM genipin at 50 °C for 5 h and with 5 mM genipin at 50 °C for 5 h, respectively. In LMWH microspheres, the best release profile corresponded to 0.5 mM genipin, 50 °C, 5 h. In conclusion, genipin showed to be eligible as a chemical-crosslinking agent delaying the outflow of drugs from the microspheres. However, more studies in vitro and in vivo must be carried out to determine adequate crosslinking conditions for different drugs.

Establishment of replacement batches for heparin low-molecular-mass for calibration CRS, and the International Standard Low Molecular Weight Heparin for Calibration

An international collaborative study involving fourteen laboratories has taken place, organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM) with National Institute for Biological Standards & Control (NIBSC) (in its capacity as a World Health Organisation (WHO) Laboratory for Biological Standardisation) to provide supporting data for the establishment of replacement batches of Heparin Low-Molecular-Mass (LMM) for Calibration Chemical Reference Substance (CRS), and of the International Reference Reagent (IRR) Low Molecular Weight Heparin for Molecular Weight Calibration. A batch of low-molecular-mass heparin was donated to the organisers and candidate preparations of freeze-dried heparin were produced at NIBSC and EDQM. The establishment study was organised in two phases: a prequalification (phase 1, performed in 3 laboratories in 2005) followed by an international collaborative study (phase 2). In phase 2, started in March 2006, molecular mass parameters were determined for seven different LMM heparin samples using the current CRS batch and two batches of candidate replacement material with a defined number average relative molecular mass (Mn) of 3,700, determined in phase 1. The values calculated using the candidates as standard were systematically different from values calculated using the current batch with its assigned number-average molecular mass (Mna) of 3,700. Using raw data supplied by participants, molecular mass parameters were recalculated using the candidates as standard with values for Mna of 3,800 and 3,900. Values for these parameters agreed more closely with those calculated using the current batch supporting the fact that the candidates, though similar to batch 1 in view of the production processes used, differ slightly in terms of molecular mass distribution. Therefore establishment of the candidates was recommended with an assigned Mna value of 3,800 that is both consistent with phase 1 results and guarantees continuity with the current CRS batch. In phase 2, participants also determined molecular weight parameters for the seven different LMM heparin samples using both the 1st IRR (90/686) and its Broad Standard Table and the candidate World Health Organization (WHO) 2nd International Standard (05/112) (2nd IS) using a Broad Standard Table established in phase 1. Mean molecular weights calculated using 2nd IS were slightly higher than with 1st IRR, and participants in the study indicated that this systematic difference precluded establishment of 2nd IS with the table supplied. A replacement Broad Standard Table has been devised on the basis of the central recalculations of raw data supplied by participants; this table gives improved agreement between values derived using the 1st IRR and the candidate 2nd IS. On the basis of this study a recommendation was made for the establishment of 2nd IS and its proposed Broad Standard Table as a replacement for the 1st International Reference Reagent Low Molecular Weight Heparin for Molecular Weight Calibration. Unlike the 1st IRR however, the candidate material 2nd IS is not suitable for use with the method of Nielsen. The candidate materials were established as heparin low-molecular-mass for calibration batches 2 and 3 by the Ph. Eur. Commission in March 2007 and as 2nd IS low-molecular-weight heparin for molecular weight calibration (05/112) by the Expert Committee on Biological Standardization in November 2007.

Quantitative determination of disaccharide content in digested unfragmented heparin and low molecular weight heparin by direct-infusion electrospray mass spectrometry

Heparins and low molecular weight heparins (LMWHs) are heterogeneous glycosaminoglycans derived from natural sources that are prescribed as anticoagulants. In this work, a direct-infusion electrospray ionization mass spectrometry (ESI-MS) method was applied to the quantitative analysis of known disaccharides in various native heparins and LMWHs after digestion with heparinase enzymes. Disaccharide deltaUA2S-->GlcNS6S was found to compose the majority of all samples analyzed (81-88%). The values were significantly higher than those reported by previously published methods. The disaccharide isomer pair deltaUA-->GlcNS6S/deltaUA2S-->GlcNS was also detected in all samples at lower levels (11-19%). While digestion with heparinases I and II revealed a limited number of disaccharides, the addition of heparinase III to digests led to the detection of disaccharide deltaUA2S-->GlcNAc6S in native porcine heparin. This result indicated the importance of utilizing all three heparinases to gain maximum information when analyzing heparin and LMWH digests. This method displayed good between-day (4-6%) and between-digest (1-2%) reproducibility in separate experiments. To determine if the digestion matrix was suppressing the signal of low-abundance disaccharides, several disaccharides were exogenously added at low levels (1-10 pmol/mg) to a quenched digest reaction. Analysis revealed that low level disaccharides were detectable in this matrix above the limits of detection (0.1-0.2 pmol/mg) and quantitation (0.2-0.7 pmol/mg). While this method was unable to distinguish between disaccharide isomers, it utilized simple mass spectrometry instrumentation to provide useful quantitative data for characterizing preparations of native heparin and LMWH, which could be used to compare various marketed preparations of these popular anticoagulants.

Inhibition of extrinsic hemostasis activation by low-molecular-weight heparin

Low-molecular-weight heparins (LMWHs) are very important drugs; unfortunately, the routine global hemostasis assays activated partial thromboplastin time and prothrombin time are not sensitive to LMWHs. Here the 50% inhibitory concentration (IC(50)) values of heparin and LMWHs on extrinsic thrombin generation are determined. Pooled normal plasma was supplemented with 0-2 IU/ml unfractionated heparin, 0-2 IU/ml LMWH dalteparin, or 0-20 microg/ml pentosanpolysulfate in 5-ml polystyrole tubes (23 degrees C) and tested in the tissue-factor-triggered extrinsic coagulation activity assay (EXCA): 50 microl plasma + 5 microl tissue factor/CaCl(2), 1 and 2 min incubation time at 37 degrees C (coagulation reaction time for EXCA-1 and EXCA-2); + 100 microl of 2.5 mol/l arginine (pH 8.6), 20 min at room temperature; + 50 microl of 1 mmol/l CHG-Ala-Arg-pNA, 1.25 mol/l arginine; increase in absorbance/time at 23 degrees C; calibrator = 1 IU/ml bovine thrombin in 6.7% human albumin replacing the plasma sample; in EXCA-1, about 1 IU/ml thrombin is generated in pooled unfrozen normal citrated plasma. The IC(50) values in EXCA-1 are 0.1 IU/ml heparin, 0.02 IU/ml LMWH, and 4.7 microg/ml pentosanpolysulfate. In ECXA-2 the IC(50) values are 0.07 IU/ml, 0.01 IU/ml, and 4.6 microg/ml, respectively. The EXCA reflects the efficiency of anticoagulants on plasmatic coagulation. It is suggested to adjust the dosage of LMWH according to the EXCA value; about 30% of normal extrinsic thrombin generation might be the correct dose for prophylactic anticoagulation.

Capillary zone electrophoresis characterization of low molecular weight heparin binding to interleukin 2

A method based on capillary zone electrophoresis (CZE) was used to study the interaction between low molecular weight heparin (LMWH) and interleukin 2 (IL-2). The results showed that the increase of the concentration of LMWH led to the decrease of the peak height and the increase of the peak width of IL-2, but the peak areas were kept constant. The binding constant of IL-2 with LMWH was calculated as 1.2 x 10(6)M(-1) by Scatchard analysis, which is in good agreement with the results found in the references using enzyme-linked immunosorbent assay (ELISA). The results demonstrated that the interaction between IL-2 and LMWH is of fast on-and-off kinetic binding reaction. CZE might be used to study not only slow on-and-off rates interactions, but also fast on-and-off rates ones. The binding constant can be calculated easily, and the method can be applied to study a wide range of heparin-protein interactions.

Collaborative study to establish the Low-molecular-mass heparin for assay--European Pharmacopoeia Biological Reference Preparation

Thirty laboratories participated in a collaborative study to calibrate replacements for the 1st International Standard for Low Molecular Weight Heparin and the European Pharmacopoeia Low-molecular-mass heparin for assay Biological Reference Preparation. Two freeze-dried materials and one liquid preparation were included in the study. All three samples gave excellent intra- and inter-laboratory variations (majority of mean % geometric coefficient of variation < 10 %) when assayed against the 1st International Standard by both anti-Xa and anti-IIa assays. There were no major differences found between potency estimates using all methods and that obtained using European Pharmacopoeia method only. Overall, this study showed that the differences between the candidates are marginal. Based on the results of the study Sample B, 01/608 was established as the 2nd International Standard for Low Molecular Weight Heparin. Sample A, 01/592 and sample C, the liquid preparation, were established as replacements for the European Pharmacopoeia 'Low-molecular-mass heparin for assay' Biological Reference Preparation.

On-line size-exclusion chromatography/mass spectrometry of low molecular mass heparin

Heparin and low molecular mass heparin (LMMH) consists of complex mixtures of sulphated linear oligosaccharides that are difficult to analyse. An on-line size exclusion chromatographic/electrospray ionization (ESI) mass spectrometric method that allows the determination of more than 60 components in an LMMH preparation is presented. The experimental setup includes on-line cation exchange in order to prevent massive adducting in the ESI interface.

Capillary electrophoresis for characterization of low molecular weight heparins

In many instances, low molecular weight heparins (LMWH) have replaced unfractionated heparins for prevention and treatment of venous thromboembolism. Each LMWH is a specific compound with its own physicochemical and pharmacological properties. These properties are critical in determining the therapeutic efficacy of the product. In recent times, capillary electrophoresis (CE) has emerged as a means of analytical separation of biological molecules. There are few reports, however, detailing the separation of whole heparins by capillary electrophoresis. This paper reports the use of CE to characterize LMWH without prior oligosaccharide release, labeling, or derivatization. The paper also focuses on the advantages of CE separation for the monitoring of product consistency.

Enhanced sensitivity electrochemical assay of low-molecular-weight heparins using rotating polyion-sensitive membrane electrodes

Use of a novel rotating polycation-sensitive polymer membrane electrode yields sensors that can serve as simple potentiometric titration endpoint detectors for the determination of three FDA approved low-molecular-weight heparin (LMWH) anticoagulant drugs (Fragmin, Normiflo, and Lovenox). The rotating electrode configuration dramatically improves the reproducibility and increases the sensitivity for LMWH determinations by protamine titration. At a rotation speed of 3000 rpm, electrodes with optimized thin (50 microm) polymer membranes doped with dinonylnaphthalene sulfonate (DNNS) respond to low levels of protamine (<2 microg mL(-1)) with good precision (+/-1 mV, N=10), when protamine is infused continuously into a Tris-buffer solution, pH 7.4. When infusing protamine (at 5 microg min(-1)) continuously into solutions containing Fragmin, a clear endpoint is obtained, with the amount of protamine required to reach this endpoint proportional to the level of Fragmin present. A detection limit of less than 0.02 U mL(-1) Fragmin can be obtained via this new method, approximately one order of magnitude lower than that previously reported based on a non-rotating polycation electrode. Similar low detection limits can be achieved for potentiometric titrations of Normiflo and Lovenox. Such titrations can also be carried out in undiluted plasma samples containing the various LMWH species. In this case, detection of the LMWHs at clinically relevant concentrations (>0.2 U mL(-1)) can be readily achieved.

Low molecular weight heparins: differences and similarities in approved preparations in the United States

There is adequate preclinical data to support the differential biochemical and pharmacological behavior of the currently approved low molecular weight heparins (LMWHs) in the United States. Initial studies on the anti-Xa, anti-IIa, and U.S. Pharmacopoeial (USP) potencies have clearly demonstrated differences among these products. Furthermore, the ratios between the anti-X and anti-IIa activities vary from one product to another. This is primarily due to the composition of each product manufactured by using different patented methods. Studies in pharmacologic animal models, using gravimetric dosages or adjusted anti-Xa dosages of the LMWHs, produce product-specific results. The pharmacokinetics and pharmacodynamics of each product also vary markedly and are not predictable on the basis of any pharmacopoeial potency designation. These agents are capable of releasing tissue factor pathway inhibitor (TFPI), an inhibitor of the coagulation process. Its release is also dependent on the type of LMWH. In the United States enoxaprin, dalteparin, and ardeparin have been approved for DVT prophylaxis. Only enoxaparin and dalteparin have been approved for the acute coronary syndrome. Recently the clinical differentiation among these LMWHs has been demonstrated in the treatment of acute coronary syndrome. Similarly, when these drugs are used at high dosages, they are expected to produce product-specific pharmacodynamic effects. It must be noted that while these drugs may be interchangeable at clinically optimized/approved dosages, these drugs are not interchangeable at equivalent anti-Xa dosages. Even at optimized dosages, the clinical provile of each drug may be different. Thus, each of the LMWHs should be considered a distinct entity and their use in a given clinical situation should be validated in proper clinical trials.

Determination of low-molecular-weight heparins and their binding to protamine and a protamine analog using polyion-sensitive membrane electrodes

A polycation-sensitive membrane electrode based on the ion-exchanger dinonylnaphthalene sulfonate has previously been developed and used as an end-point detector for the determination of unfractionated heparin in whole blood samples via simple potentiometric titration with protamine. Herein, we report the application of the same methodology for the quantitation of a commercial low-molecular-weight heparin (LMWH) preparation (Fragmin) in whole blood samples at concentrations up to 2 U/ml. Further, an analogous polyanion (heparin)-sensitive electrode is used to estimate the binding constants between protamine and various LMWH preparations. The equilibrium constants (Keq) and the number of binding sites per mole of heparin (n) are determined by recasting the data in the form of a Scatchard plot. Results show that the average molecular weight and molecular weight distribution of the LMWH preparation are important parameters affecting their binding with protamine. Comparable binding constants are obtained for the same LMWH preparations titrated with a synthetic protamine analog, [+18RGD] [acetyl-EA(R2A2R2A)4R2GRGDSPA-NH2].

Heparins, low-molecular-weight heparins, and other glycosaminoglycans analyzed by agarose gel electrophoresis and azure A-silver staining

A sensitive, nonradioactive azure A-silver staining method combining agarose gel electrophoresis was established and evaluated. Unfractionated heparins (UFHs), low-molecular-weight heparins (LMWHs), heparan sulfate (HS), chondroitin sulfate A (CSA), dermatan sulfate (DS), keratan sulfate (KS), and hyaluronic acid (HA) were analyzed. The detection limit of the method was 0.5 ng for heparin, LMWH, HA, CSA, and DS, 2 ng for KS, and 6 ng for HA in the 2-microliter sample volume. Dilution curves demonstrated linear correlation between the logarithm of the concentration of glycosaminoglycans (GAGs) and their optical absorbance at 548 nm. The linear ranges were 1 to 500 ng/microliter for heparins, LMWHs, HS, DS, and CSA, 3 to 500 ng/microliter for KS, and 8 to 500 ng/microliter for HA. GAGs have their characteristic migration patterns and their Rf value decreased from CSA to KS, DS, HS, heparin, and HA. The differences were described for heparins and LMWHs. LMWHs migrated faster and displayed broader bands than unfractionated heparins. It was also observed that some unfractionated heparins contained low sulfated GAGs as contamination, which seemed to be DS as judged by their migration patterns.

Purification of the monoclonal heparin antibody H-1.18

An antibody of the (immunoglobulin) IgG1 subclass against heparin was purified. Here we report on the purification of the heparin antibody. Ammonium sulfate precipitation was performed and showed a high purity of the precipitate. In the heparin radioimmunoassay it showed a high heparin binding. Capillary electrophoresis showed that albumin and other proteins were separated from the heparin antibody. The purification method allowed a large scale production of the heparin antibody.

Feasibility study of heparin mass calibrator as a GPC calibrator for heparins and low molecular weight heparins

The proposed European Pharmacopoeial (EP) method for molecular weight determination of low molecular weight heparins (LMWHs) has been shown to have a range which is too narrow to allow for the accurate molecular weight determinations of all LMWHs. We have recently shown that a chemically degraded benzyl ester of unfractionated heparin, ITH-3, is a better calibrator using this methodology. Data is presented here which indicates that this calibrator cannot only be used to determine the molecular weights of LMWHs but also of unfractionated heparins. Therefore, it is now renamed heparin mass calibrator or HMC because of this extension of range. Weight average molecular weight, number average molecular weight, peak molecular weight, and dispersity values were calculated using the HMC calibration and a reference narrow-range 19-calibrator method for various LMWHs and unfractionated heparins. Values for the parameters calculated using the HMC calibration were found not to be significantly different from those of the reference method until the molecular weight exceeded 15.0 kDa. In contrast, the molecular weight profile obtained with the proposed EP method was significantly different from the reference method for samples > 8.0 kDa. The range exhibited by the HMC calibrator should allow it to be used for both LMWHs and unfractionated heparins.

Characterization of heparins with different relative molecular masses (from 11,600 to 1600) by various analytical techniques

Heparin was extracted and purified from beef intestinal mucosa, and its structure and physico-chemical properties, e.g. disaccharide pattern (by specific enzymatic cleavage), relative molecular mass and sulfate-to-carboxyl ratio, were evaluated by different techniques. Heparin fractions with different relative molecular mass (from M(r) = 7560 to M(r) = 1600) were prepared by chemical degradation and gel-permeation chromatography. The fractions were characterized with respect to relative molecular mass, disaccharide pattern, sulfate-to-carboxyl ratio and percentage of slow moving and fast moving components by agarose-gel electrophoresis. The percentage of the two heparin species was calculated by densitometric analysis and specific calibration curves. The amount of the slow moving component decreases with relative molecular mass. The disaccharide pattern is different for the two heparin fractions. The percentage of trisulfated disaccharide decreases and the amount of mono- and disulfated disaccharides increases with a decrease of the relative molecular mass. The charge density, evaluated as the sulfate-to-carboxyl ratio, also decreases with the molecular mass of the fractions. This study confirms the heterogeneity of the structure, as evaluated by the constituent disaccharides, of the physico-chemical properties, such as relative molecular mass and charge density, and of the relative amount of the two heparin components also for low molecular mass heparins particularly produced by chemical depolymerization in the presence of free radicals.

Oligosaccharide composition of heparin and low-molecular-weight heparins by capillary electrophoresis

The application of capillary electrophoresis to total compositional analysis of heparin and low-molecular-weight heparin samples has been studied. Optimum resolution of 17 defined oligosaccharides was obtained with the buffer system composed of 10 mM sodium borate and 50 mM sodium dodecyl sulfate at pH 8.81 and at a constant voltage of 20 kV. The ratio of oligosaccharide charge to the number of saccharide residues correlated with the migration time. For oligosaccharides having the same charge to saccharide ratio, the larger of the oligosaccharides eluted earlier. A hexasaccharide having a 3-O-sulfated glucosamine residue at the reducing end and arising from heparin's antithrombin III binding site, migrated in an unusual fashion. The limit of oligosaccharide detection was from 600 fmol to 1 pmol. Quantitative analysis could conveniently be performed on 10 pmol of an oligosaccharide sample. Oligosaccharide composition using capillary electrophoresis was obtained by nearly complete depolymerization of heparins with a mixture of heparin lyase I, II, and III. The analysis resulted in 95% mass balance for both heparin and low-molecular-weight heparin. Capillary electropherograms of heparin and different low-molecular-weight heparins depolymerized with heparin lyase I alone showed a high level of structural heterogeneity in the products formed. The oligosaccharide maps thus obtained might find use in fingerprinting the heparin and low-molecular-weight samples.

Evaluation of the effects of low molecular weight heparin on inflammation and collagen deposition in chronic coxsackievirus B3-induced myocarditis in A/J mice

Coxsackievirus, Group B, type 3 (CVB3) infection of A/J male mice induces chronic myocarditis with increased interstitial fibrosis and collagen deposition. Heparin, a naturally occurring sulfated glycosaminoglycan, has both anti-inflammatory and antifibrotic activities besides its well-known anticoagulant activity. This study determined whether heparin treatment could decrease either cardiac inflammation or fibrosis in chronic CVB3-induced myocarditis. Control mice were either untreated or treated with heparin (4 micrograms/g body weight, subcutaneously 5 times weekly) beginning 2 days before infection of other groups. Additional groups received either virus only (1 x 10(4) plaque-forming units [PFU]), virus followed by heparin beginning 14 days after CVB3 inoculation, or virus and heparin beginning 2 days before CVB3 inoculation. Animals were sacrificed 14, 28, and 58 days after infection. Heparin treatment begun either before or after virus inoculation reduced animal mortality by approximately 20%. Heparin did not alter virus infection or replication in the heart. Histologically, only animals treated with heparin before virus inoculation showed reduced myocardial inflammation, and only at day 58. However, heparin treatment begun either before or after virus infection significantly decreased collagen deposition in the heart (fibrosis).

Oligosaccharide mapping of low molecular weight heparins: structure and activity differences

Low molecular weight heparins from a variety of commercial sources were examined. These had been prepared by several methods including peroxidative cleavage, nitrous acid cleavage, chemical beta-elimination, enzymatic beta-elimination, and chromatographic fractionation. The molecular weight and polydispersity of these low molecular weight heparins showed greater differences than were observed for typical commercial heparin preparations. Considerable differences were also observed in the antithrombin III mediated anti factor Xa activity, the heparin cofactor II mediated antifactor IIa activity, and the USP activity of these low molecular weight heparins. An oligosaccharide-mapping technique (comparable to the peptide mapping of proteins) was applied to these low molecular weight heparins in an effort to understand the structural features responsible for their activity differences. Heparin lyase from Flavobacterium heparinum was first used to depolymerize the low molecular weight heparin into its constituent oligosaccharides. The oligosaccharides present in the resultant mixture were identified and quantitated by using standard oligosaccharides of defined structure on gradient polyacrylamide gel electrophoresis and strong anion exchange high pressure liquid chromatography. Six of the oligosaccharide products have been identified and represent nearly 90 wt % of heparin's mass. Even though all the low molecular weight heparins showed these six oligosaccharide components, their content in each varied greatly, accounting for 20 to over 90% of their mass. The antithrombin III mediated anti factor Xa activities of the low molecular weight heparins correlated only poorly to the concentration of a hexasaccharide containing a portion of heparin's antithrombin III binding site. The heparin cofactor II mediated antifactor IIa activity, however, could not be correlated to these six oligosaccharides of known structure nor to the molecular weight or charge density of these low molecular weight heparins. The low molecular weight heparins prepared by different methods each showed a new distinctive oligosaccharide in their maps. Their isolation and structural characterization, which included two-dimensional NMR and fast atom bombardment mass spectrometry, indicated that these unusual oligosaccharides result from end-sugar modification during chemical depolymerization. Both gel electrophoresis and high-pressure liquid chromatography mapping techniques showed a greater structural diversity between low molecular weight heparins than had previously been observed between similarly analyzed commercial heparins.

Physicochemical characterization of the First World Health Organization International Standard for low molecular weight heparin derivatives

High-field (300 MHz) 1H NMR spectral analysis and particle size distribution analysis employing the quasielastic light scattering (QELS) technique were performed on samples of the 1st International Standard for low molecular weight (LMW) heparin derivatives recently selected by the World Health Organization (WHO). We propose that the results of these analyses, which showed that the material is highly homogeneous in particle size and retains spectral features characteristic of its porcine mucosal origin, form an appropriate basis for physicochemical comparison between the "Standard" and other LMW heparin preparations.

Chemical composition, particle size range, and biological activity of some low molecular weight heparin derivatives

Several low molecular weight (LMW) heparin sodium derivatives from different sources, as well as some related regular heparin sodium preparations, were examined for chemical composition by high field (300 MHz) 1H NMR spectroscopy, for particle size range by quasi-elastic light scattering (QELS) methods, and for anti-coagulation potency and anti-factor Xa activity by the standard U.S. Pharmacopeial assays described for regular heparin. The NMR spectra provided insight into possible modes of depolymerization used to generate the LMW heparins, as well as into the presence of dermatan sulfate or other chemical contaminants. The QELS analysis permitted the heparin preparations to be characterized and compared by virtue of their distinctive particle size distributions.

In vitro effect on Heptest of low molecular weight heparin fractions and preparations with various anti-IIa and anti-Xa activities

The Heptest heparin assay has recently been introduced, and evaluated for the laboratory monitoring of patients receiving low molecular weight heparins (LMWH). The aim of the present study was to elucidate the relative role on the Heptest assay of the anti-factors Xa and IIa activities present in the three types of compounds that possess: 1. exclusively anti-Xa activity (LF1: LMWH fractions with MW ranging from 1,200 to 4,200 D.); 2. both anti-Xa and anti-IIa activities (LF2 with MW from 4,800 to 12,000 D.); 3. exclusive anti-IIa activity (Hirudin and Dermatan Sulfate). All compounds studied demonstrated dose-dependent activities in both amidolytic and clotting assays. The LF2 in contrast to the LF1, additionally enhanced the clotting times of Heptest. This enhancement was shown to be due to the anti-Factor IIa activity of the agents. Heptest does not exclusively reflect Anti-Xa activity since it is influenced by agents containing exclusive anti-IIa activity like Hirudin and Dermatan Sulfate. At low concentrations of LF2, Heptest measures predominantly the anti-factor Xa activity while at higher concentrations it is influenced by the combined activity of anti-factor Xa and anti-factor IIa. However, Heptest sensitivity to anti-factor IIa is significantly lower than for anti-Xa activity.

A fragmin-like protein from plasmodium of Physarum polycephalum that severs F-actin and caps the barbed end of F-actin in a Ca2+-sensitive way

Many protein factors regulating actin polymerization can be extracted from plasmodia of Physarum polycephalum in the presence of a high EGTA concentration (30 mM). A protein factor with the molecular weight of 60,000 (60 kDa protein) was especially interesting because of its fragmin-like properties. We purified and characterized this 60 kDa protein in the present study. The purified 60 kDa protein enhanced the initial rate of G-actin polymerization, severed F-actin, and capped the barbed end of F-actin in a Ca2+-dependent way. The threshold concentration for Ca2+ was around 10(-6) M. The flow birefringence measurement showed that the length of F-actin decreased from 2.8 to 1.0 microns depending on the concentration of 60 kDa protein added to F-actin. These properties were identical to those of fragmin (Mr 42,000) isolated from plasmodia (Hasegawa et al. (1980) Biochemistry 19, 2677-2683). However, the molecular weight, the tryptic peptide map, and the cross-reactivities with polyclonal anti-fragmin antibodies were different from those of fragmin. We concluded from these results that 60 kDa protein is a new Ca2+-sensitive F-actin-severing protein. Considering its similarity to fragmin, we termed the 60 kDa protein fragmin 60.

Monitoring the purity of pharmaceutical heparin preparations by high-field 1H-nuclear magnetic resonance spectroscopy

High-field (300 MHz) 1H NMR spectral analyses are reported for various sodium or calcium heparin products available on the Canadian market. Dermatan sulfate (chondroitin sulfate B) was detected as a contaminant in virtually all of these products. Its content varied among the suppliers from less than 1 to 15%, and also over nearly the same range within the groups of heparin preparations of particular suppliers. No correlation was found between in vitro biological activities (potency and anti-factor Xa by the USP tests) and the levels of dermatan sulfate found. Other components, or unlisted constituents, detected in some preparations were paramagnetic metal ions, polyols, and lidocaine.