The Measurement of Heparin and Other Therapeutic Sufphated Polysaccharides in Plasma, Serum and Urine

1985 ◽  
Vol 54 (03) ◽  
pp. 630-634 ◽  
Author(s):  
J Dawes ◽  
C V Prowse ◽  
D D Pepper
Keyword(s):  
Biological Fluids ◽  
Anticoagulant Activity ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Heparin Therapy ◽  
Competitive Binding Assay ◽  
First Order Kinetics ◽  
Activity Measurements ◽  
Heparin Activity ◽  
Dose Dependent

SummaryThe competitive binding assay described will specifically and accurately measure concentrations of administered heparin in biological fluids with a sensitivity of 60 ng ml-1. Neither endogenous glycosaminoglycans, nor plasma proteins such as ATIII and PF4 interfere in the assay. Semi-synthetic highly sulphated heparinoids and LMW heparin can also be measured. Using this assay heparin clearance followed simple first-order kinetics over the dose range 100-5,000 units, but the half-life was strongly dose-dependent. There was good correlation with heparin activity measurements by APTT and anti-Xa clotting assays. Plasma concentrations were measurable for at least 5 h following subcutaneous injection of 10,000 units of heparin. Excretion in the urine could be followed after all but the lowest intravenous dose. This assay, used in conjunction with measurements of heparin anticoagulant activity, will be valuable in the elucidation of mechanisms of action of heparin and the heparinoids, and in the assessment and management of problems related to heparin therapy.

Reversal of Dabigatran's Anticoagulant Activity in the Monkey by a Specific Antidote and Pharmacokinetic and Pharmacodynamic Modeling

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 22-22 ◽  
Author(s):  
Joshuaine Toth ◽  
Guanfa Gan ◽  
Joanne van Ryn ◽  
Holly Dursema ◽  
Jennifer Isler ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Anticoagulant Activity ◽  
Plasma Concentrations ◽  
Mass Action ◽  
Pharmacodynamic Modeling ◽  
Dependent Manner ◽  
Thrombin Time ◽  
Binding Interaction ◽  
Mass Action Kinetics ◽  
Dose Dependent

Abstract Abstract 22 Background: The objective of this study is to determine the pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran (a small molecule thrombin inhibitor) and its antidote (a humanized Fab against dabigatran) in the monkey and to develop a combined mechanistic mathematical model to describe the data. Methods: There were three groups: control, antidote alone and dabigatran etexilate (DE) + antidote. Rhesus monkeys (n = 2/group) received either 12 mg/kg/day of DE or vehicle orally on Days 1–4, 15–18 and 29–32 with a single IV dose of the antidote administered 90 minutes after DE on Days 4, 18 and 32. Doses of the antidote were 30, 90 or 175 mg/kg, respectively. PK parameters of the antidote and sum dabigatran (dabigatran plus its glucuronides) were determined after measurements of plasma concentrations. Coagulation activity was measured using a diluted thrombin time assay to determine the activity of the unbound sum dabigatran. Results: The PK of the antidote were not affected by dabigatran. Clearance of the antidote was low (0.87 mL/min/kg) and steady-state volume of distribution was small (0.06 L/kg), indicating that the antidote was mostly restricted to plasma. The plasma profile of the antidote was bi-phasic with a short initial phase t1/2 of 0.4 hour (h) and a terminal phase t1/2 of 4.3 h. Immediately after antidote dosing, plasma concentrations of sum dabigatran increased, a consequence of the rapid redistribution of dabigatran and its glucuronides from tissue to plasma due to binding to the antidote. Complete reversal of dabigatran's anticoagulant activity was observed immediately after antidote dosing at all three dose levels, as measured by the diluted thrombin time assay, which indicates that all dabigatran was bound to the antidote. The degree to which this reversal effect was maintained over an extended period (24 h) was dose-dependent. A mechanistic ordinary differential equation model, based on the mass action kinetics for describing the distribution, binding and elimination of dabigatran and its antidote, was developed by combining the PK models for dabigatran and the antidote and adding the binding interaction (1:1 stoichiometry) between the two compounds. The distribution and elimination parameters of the dabigatran-antidote complex were assumed to be the same as those of the antidote, based on similar measured PK parameters of the antidote with and without dabigatran in the monkey. The combined PK/PD model of dabigatran and antidote was able to describe the in vivo PK/PD data observed in monkeys. Conclusion: The dabigatran-specific antidote successfully reversed the anticoagulant activity of dabigatran in the monkey in a dose-dependent manner, and our combined mathematical model accurately describes monkey PK/PD data of sum dabigatran and its antidote. Insights gained from this model will be used to guide model development for clinical trials. Disclosures: Toth: Boehringer Ingelheim: Employment. Gan:Boehringer Ingelheim: Employment. van Ryn:Boehringer Ingelheim: Employment. Dursema:Boehringer Ingelheim: Employment. Isler:Boehringer Ingelheim: Employment. Coble:Boehringer Ingelheim: Employment. Burke:Boehringer Ingelheim: Employment. Lalovic:Boehringer Ingelheim: Employment. Olson:Boehringer Ingelheim: Employment.

Metabolism of Sodium Pentosan Polysulphate in Man Measured by a New Competitive Binding Assay for Sulphated Polysaccharides – Comparison with Effects Upon Anticoagulant Activity, Lipolysis and Platelet α-Granule Proteins

1985 ◽  
Vol 53 (03) ◽  
pp. 411-414 ◽  
Author(s):  
I R MacGregor ◽  
J Dawes ◽  
D S Pepper ◽  
C V Prowse ◽  
J Stocks
Keyword(s):  
Binding Assay ◽  
Peak Plasma ◽  
Anticoagulant Activity ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Competitive Binding ◽  
Platelet Factor ◽  
Competitive Binding Assay ◽  
Sulphated Polysaccharides ◽  
Pentosan Polysulphate

SummaryThree human volunteers were injected with a range of doses of pentosan polysulphate, SP54, i.v. or s.c. A competitive binding assay (CBA) for sulphated polysaccharides was used to detect circulating SP54 after doses as low as 1 mg i.v. and a linear relationship was observed between the peak plasma concentration of SP54 measured by CBA and the administered dose. A comparison was made between the clearance of SP54 measured by CBA and its anticoagulant and lipolytic activities. SP54 was detectable by CBA after doses which caused no alteration in activated partial thromboplastin time (APTT) or anti-factor Xa activity but after which a small increase of lipase activity was measurable. After SP54 at 10 mg i.v. or 100 mg s.c. anti-factor Xa activity was 4-6 times greater than would be expected from the in vitro activity of the concentrations of SP54 measured by CBA. Like heparin and other heparin analogues, SP54 caused an increase in plasma concentrations of platelet factor 4 (PF4) without a concomitant rise in p-thromboglobulin (β-TG).It is concluded that the newly developed CBA will provide a more sensitive means than conventional bioassays for the determination of plasma concentrations of SP54.

Effect of heparin and its derivatives on the progression of tumor growth in mouse Lewis lung carcinoma model.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. e13115-e13115
Author(s):  
Angel Gray ◽  
Debra Hoppensteadt ◽  
Matthew Hejna ◽  
Jawed Fareed
Keyword(s):  
Tumor Growth ◽  
Anticoagulant Activity ◽  
Dose Range ◽  
Saline Control ◽  
Spleen Weight ◽  
Dependent Manner ◽  
Heparin Group ◽  
Prevention Of Cancer ◽  
Cancer Associated Thrombosis ◽  
Dose Dependent

e13115 Background: Preclinical evidence suggests that heparins have an effect on tumor progression independent of their anticoagulant activity. Heparins have also been shown to exhibit interactions with growth factors and other cellular receptors. This study was designed to investigate whether heparin and its derivatives are able to inhibit tumor growth. Methods: Female C57BL/6 mice were obtained at 6-8 weeks of age and were implanted with 5X105 LN7 tumor cells by dorsal subcutaneous injection of in the upper back. When tumors were first palpable, after 7-10 days of growth, mice were treated with subcutaneous injections of heparin, a low molecular weight heparin (LMWH), namely enoxaparin, an ultra LMWH, semuloparin or saline, daily for two weeks in a dose range of 1.0 – 0.25 mg/kg. After the treatment period, animals were sacrificed and the spleens and tumors were removed and their weight, volume, spleen weight and size were measured. Results: At the 1.0 and 0.5 mg/kg dosages, both enoxaparin (p<0.01) and semuloparin (p<0.01) showed a decrease in tumor volume compared to the saline control animals. At the 1.0 mg/kg dosage, the mortality was high in the heparin group due to bleeding. At 0.5 mg/kg heparin was not different from the saline control. In addition, at a dosage of 0.25 mg/kg, only semuloparin showed a difference compared to the saline control (p<0.01). Similar results were observed for the tumor weight. There were no significant differences noted in spleen weight or spleen size among these agents. The mortality rates between the mice treated with enoxaparin and semuloparin were comparable. Conclusions: These studies suggest that heparin and its derivatives are capable of inhibiting tumor growth in a dose dependent manner. Enoxaparin and semuloparin are more effective at reducing tumor growth compared to heparin. Clinical studies have shown that semuloparin is safe and effective for the prevention of venous thromboembolism in cancer patients and compares favorably to enoxaparin in terms of antithrombotic effect and safety profile. Therefore, semuloparin may be a better alternate for the prevention of cancer associated thrombosis.

Safety, pharmacokinetics and pharmacodynamics of single doses of rivaroxaban – an oral, direct factor Xa inhibitor – in elderly Chinese subjects

2010 ◽  
Vol 103 (01) ◽  
pp. 234-241 ◽  
Author(s):  
Ji Jiang ◽  
Yufang Hu ◽  
Jianyan Zhang ◽  
Jueling Yang ◽  
Wolfgang Mueck ◽  
...  
Keyword(s):  
Dose Range ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Maximum Plasma ◽  
Direct Factor ◽  
Dose Escalation Study ◽  
Healthy Elderly ◽  
Elderly Chinese ◽  
Dose Dependent ◽  
Chinese Subjects

SummaryRivaroxaban is a novel, oral, direct factor Xa (FXa) inhibitor for the prevention and treatment of thromboembolic disorders. The aim of this study was to investigate the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of rivaroxaban in healthy, elderly Chinese subjects. In this single-centre, single-blind, placebo-controlled, parallel-group, dose-escalation study, 79 subjects, aged 59–74 years (mean 62.8), were randomised to receive once-daily oral doses of rivaroxaban 5, 10, 20, 30 or 40 mg. Rivaroxaban was well tolerated: there was a low incidence of treatment-emergent adverse events and all events were of mild intensity. Rivaroxaban was absorbed rapidly, reaching maximum plasma concentrations within 2–4 hours. The PK of rivaroxaban were dose dependent over the dose range tested. Maximal inhibition of FXa occurred 2–3 hours after dosing and returned to baseline after 24–48 hours, reflecting rivaroxaban plasma concentrations. Inhibition of FXa was associated with dose-dependent effects on global clotting tests. There were no clinically relevant differences in rivaroxaban plasma concentrations between male and female subjects. In conclusion, rivaroxaban was well tolerated and was found to have predictable PK and PD in healthy, elderly Chinese subjects.

Abstract WP273: Reversal of Dabigatran’s Anticoagulant Activity in the Monkey by a Specific Antidote and Pharmacokinetic and Pharmacodynamic Modeling

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Joshuaine Toth ◽  
Guanfa Gan ◽  
Joanne Van Ryn ◽  
Holly Dursema ◽  
Jennifer Isler ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Anticoagulant Activity ◽  
Plasma Concentrations ◽  
Mass Action ◽  
Pharmacodynamic Modeling ◽  
Dependent Manner ◽  
Thrombin Time ◽  
Binding Interaction ◽  
Mass Action Kinetics ◽  
Dose Dependent

The objective of this study is to determine pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran and its antidote (a humanized Fab against dabigatran) in the monkey and to develop a combined mechanistic mathematical model to describe the data. Rhesus monkeys (n = 2/group) received either 12 mg/kg/day of dabigatran etexilate (DE) or vehicle orally on Days 1-4, 15-18 and 29-32 with a single IV dose of the antidote at 30, 90 and 175 mg/kg administered 90 minutes after DE on Days 4, 18 and 32. PK parameters of the antidote and sum dabigatran (dabigatran plus its glucuronides) were determined after measurements of plasma concentrations. Coagulation activity was measured using a diluted thrombin time assay. The PK of the antidote were not affected by dabigatran. Clearance of the antidote was low (0.87 mL/min/kg) and steady-state volume of distribution was small (0.06 L/kg), indicating that the antidote was mostly restricted to plasma. The plasma profile of the antidote was bi-phasic with a short initial phase t 1/2 of 0.4 hour (h) and a terminal phase t 1/2 of 4.3 h. Complete reversal of dabigatran’s anticoagulant activity was observed immediately after antidote dosing at all 3 dose levels as measured by the diluted thrombin time assay, and the degree to which this reversal effect was maintained over an extended period (24 h) was dose-dependent. A mechanistic ordinary differential equation model, based on the mass action kinetics for describing the distribution, binding and elimination of dabigatran and its antidote, was developed by combining the PK models for dabigatran and the antidote and adding the binding interaction (1:1 stoichiometry) between the two compounds. The combined PK/PD model of dabigatran and antidote was able to describe the in vivo PK/PD data observed in monkeys. In conclusion, the antidote successfully reversed the anticoagulant activity of dabigatran in the monkey in a dose-dependent manner, and our combined mathematical model accurately describes monkey PK/PD data of sum dabigatran and its antidote. Insights gained from this model will be used to guide model development for clinical trials.

DOSE-DEPENDENT PHARMACOKINETICS OF RECOMBINANT TISSUE-TYPE PLASMINOGEN ACTIVATOR (tPA) IN ANESTHETIZED DOGS FOLLOWING INTRAVENOUS INFUSION

1987 ◽  
Author(s):  
K L L Fong ◽  
C S Crysler ◽  
B A Mico ◽  
K E Boyle ◽  
G A Kopia ◽  
...  
Keyword(s):  
Steady State ◽  
Plasma Concentration ◽  
Plasminogen Activator ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Tissue Type ◽  
Tissue Type Plasminogen Activator ◽  
Arterial Blood ◽  
Type Plasminogen Activator ◽  
Dose Dependent

The pharmacokinetics of SK&F recombinant two-cha1n tissue-type plasminogen activator (tPA) following Intravenous (i.v.) infusion were characterized in anesthetized, open chested mongrel dogs in which artificial Intracoronary thrombi were formed. SK&F tPA was Infused at rates of 0.5, 1, 2, 4, and 8 μg/kg/min (n=3 to 5 per dose) for 90 min and arterial blood samples were withdrawn during and after Infusion for determination of functionally active tPA concentrations using a modified and validated S-2251 chromogenlc assay. At all doses studied, steady state active tPA plasma concentrations were achieved 10-20 min after the onset of Infusion. Upon cessation of Infusion, active tPA plasma concentrations declined rapidly with a t1/2 of 2-3 min. The active tPA plasma concentration at steady state (Css) and the area under the tPA plasma concentration-time curve (AUC) Increased linearly with dose in the range of 0.5-4 μg/kg/min. However, as the dose was Increased 2-fold from 4 to 8 μg/kg/min, the AUC and the Css Increased 2.5 fold. The systemic clearance ranged from 15-16 ml/min/kg at doses of 0.5-4 μg/kg/min but decreased to 11.7 ml/min/kg at the 8 μg/kg/min dose. With exceptions in 3 dogs, the volume of distribution at steady state approached or slightly exceeded the blood volume. Plasma tPA antigen concentrations were also determined in the dogs receiving the 2 μg/kg/min dose. At steady state, active tPA accounted for 40-60% of the total tPA antigen. The post-infusion t1/2 of the tPA antigen was considerably longer (13.46 ± 5.94 min) than that of active tPA. These results suggested that non-plasminogen activating metabolites (e.g., tPA-inhlbltor complex(es)) are present in the plasma of dogs receiving tPA. It 1s also concluded from the present study that (1) distribution of the i.v. administered tPA molecule was limited primarily to the Intravascular space, and (2) tPA may display dose-dependent pharmacokinetics within the optimum thrombolytic dose range.

scholarly journals Analgesic and Respiratory Depressant Effects of R-dihydroetorphine

2019 ◽  
Vol 131 (6) ◽  
pp. 1327-1339
Author(s):  
Erik Olofsen ◽  
Merel Boom ◽  
Elise Sarton ◽  
Monique van Velzen ◽  
Paul Baily ◽  
...  
Keyword(s):  
Respiratory Depression ◽  
Peak Plasma ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Pharmacokinetic Analysis ◽  
Population Pharmacokinetic ◽  
Noxious Stimulation ◽  
Orphanin Fq ◽  
Arterial Blood ◽  
Dose Dependent

Abstract Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background There is an ongoing need for potent opioids with less adverse effects than commonly used opioids. R-dihydroetorphine is a full opioid receptor agonist with relatively high affinity at the μ-, δ- and κ-opioid receptors and low affinity at the nociception/orphanin FQ receptor. The authors quantified its antinociceptive and respiratory effects in healthy volunteers. The authors hypothesized that given its receptor profile, R-dihydroetorphine will exhibit an apparent plateau in respiratory depression, but not in antinociception. Methods The authors performed a population pharmacokinetic–pharmacodynamic study (Eudract registration No. 2009-010880-17). Four intravenous R-dihydroetorphine doses were studied: 12.5, 75, 125, and 150 ng/kg (infused more than 10 min) in 4 of 4, 6 of 6, 6 of 6, and 4 of 4 male subjects in pain and respiratory studies, respectively. The authors measured isohypercapnic ventilation, pain threshold, and tolerance responses to electrical noxious stimulation and arterial blood samples for pharmacokinetic analysis. Results R-dihydroetorphine displayed a dose-dependent increase in peak plasma concentrations at the end of the infusion. Concentration-effect relationships differed significantly between endpoints. R-dihydroetorphine produced respiratory depression best described by a sigmoid EMAX-model. A 50% reduction in ventilation in between baseline and minimum ventilation was observed at an R-dihydroetorphine concentration of 17 ± 4 pg/ml (median ± standard error of the estimate). The maximum reduction in ventilation observed was at 33% of baseline. In contrast, over the dose range studied, R-dihydroetorphine produced dose-dependent analgesia best described by a linear model. A 50% increase in stimulus intensity was observed at 34 ± 11 pg/ml. Conclusions Over the dose range studied, R-dihydroetorphine exhibited a plateau in respiratory depression, but not in analgesia. Whether these experimental advantages extrapolate to the clinical setting and whether analgesia has no plateau at higher concentrations than investigated requires further studies.

Effects of Native Fucosylated Glycosaminoglycan, Its Depolymerized Derivatives on Intrinsic Factor Xase, Coagulation, Thrombosis, and Hemorrhagic Risk

2020 ◽  
Vol 120 (04) ◽  
pp. 607-619 ◽  
Author(s):  
Lutan Zhou ◽  
Na Gao ◽  
Huifang Sun ◽  
Chuang Xiao ◽  
Lian Yang ◽  
...  
Keyword(s):  
Anticoagulant Activity ◽  
Intrinsic Factor ◽  
Low Molecular Weight ◽  
High Dose ◽  
Dependent Manner ◽  
Competitive Binding Assay ◽  
Thrombosis Model ◽  
Antithrombotic Effects ◽  
Hemorrhagic Risk ◽  
Dose Dependent

AbstractA native fucosylated glycosaminoglycan from sea cucumber Holothuria fuscopunctata (nHG), mainly branched with Fuc3S4S, exhibited potent anticoagulant activity by intrinsic tenase iXase (FIXa-FVIIIa complex) and antithrombin-dependent factor IIa (FIIa) inhibition, but also had the effects of FXII activation and platelet aggregation. For screening a selective iXase inhibitor, depolymerized nHG (dHG-1 ∼ –6) and a pure octasaccharide (oHG-8) were prepared. Like nHG, dHG-1 ∼ –6 and oHG-8 could potently inhibit iXase, and competitive binding assay indicated that dHG-5 and oHG-8 could bind to FIXa. Nevertheless, dHG-5 and oHG-8 had no effects on FXII and platelet activation. nHG, dHG-5, and oHG-8 could significantly prolong the activated partial thromboplastin time of human, rat, and rabbit plasma. In the rat deep venous thrombosis model, dHG-5 and oHG-8 showed potent antithrombotic effects in a dose-dependent manner, while the thrombus inhibition rate of nHG at high dose was markedly reduced. Additionally, dHG-5 and oHG-8 did not increase bleeding at the doses up to 10-fold of the effectively antithrombotic doses compared with nHG and low molecular weight heparin in the mice tail-cut model. Considering that dHG-5 possesses strong anti-iXase and antithrombotic activities, and its preparation process is simpler and its yield is higher compared with oHG-8, it might be a promising antithrombotic candidate.

Anticoagulant Activity of Hirulog™, a Direct Thrombin Inhibitor, in Humans

1993 ◽  
Vol 69 (02) ◽  
pp. 157-163 ◽  
Author(s):  
Irving Fox ◽  
Adrian Dawson ◽  
Peter Loynds ◽  
Jane Eisner ◽  
Kathleen Findlen ◽  
...  
Keyword(s):  
Rational Design ◽  
Therapeutic Potential ◽  
Anticoagulant Activity ◽  
Subcutaneous Administration ◽  
Direct Thrombin Inhibitor ◽  
Controlled Study ◽  
Thrombin Inhibitor ◽  
Thrombin Time ◽  
Thrombotic Disease ◽  
Dose Dependent

SummaryHirulog™ (BG8967) is a direct thrombin inhibitor built by rational design using the protein hirudin as a model (Maraganore et al. [1990]; Biochemistry 29: 7095–101). In order to evaluate the therapeutic potential for hirulog in the management of thrombotic disease, the tolerability and anticoagulant activity of the agent were examined in a study of human volunteers.In a randomized, placebo-controlled study (n = 54), the intravenous infusion of hirulog over 15 min showed a rapid, dose-dependent prolongation of activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT). There was a corresponding dose-dependent increase in plasma hirulog levels. The peptide was rapidly cleared with a half-life of 36 min and a total body clearance rate for the peptide of 0.43 1 kg−1 h−1. Similar activity was observed following subcutaneous injection but with sustained pharmacodynamic and pharmacokinetic behavior. There was a significant correlation between pharmacokinetic and pharmacodynamic variables for both intravenous (r = 0.8, p <0.001) and subcutaneous administration (r = 0.7, p = 0.002).To evaluate the possible interactions of aspirin on the tolerability and anticoagulant activity of intravenous hirulog, a cross-over design was employed in eight subjects. Aspirin administration did not modify the peptide’s activity. At the administered dose of 0.6 mg kg−1 h−1 for 2 h, hirulog infusion prolonged APTT from 230 to 260% baseline. The infusion of hirulog in subjects who had received aspirin was not associated with any significant changes in the template bleeding time.The final phase of the study examined the activity and tolerability of hirulog in ten subjects during prolonged intravenous infusions for up to 24 h. The peptide (0.3 mg kg−1 h−1) exhibited sustained anticoagulant activity with no evidence for a cumulative effect. During hirulog infusion, APTT was prolonged from 210 to 250% baseline.In all phases of the study, hirulog administration was generally well-tolerated.Our observations show that hirulog is an active antithrombin agent with excellent tolerability in humans. As a direct thrombin inhibitor, hirulog provides a novel approach for the management of thrombotic disease.

The Disappearance of Heparin Activity with Liver Globulins and Determinations of Heparinase

1963 ◽  
Vol 10 (01) ◽  
pp. 071-080 ◽  
Author(s):  
L. B Jaques ◽  
C Mary Jaques
Keyword(s):  
Anticoagulant Activity ◽  
Rabbit Liver ◽  
Dissociation Curve ◽  
Ph Values ◽  
Phenol Extraction ◽  
Progressive Loss ◽  
Heparin Activity

SummaryPreparations were made of rabbit liver globulin by the method of Jaques for heparinase and their effect on heparin studied. The results confirmed the observations of a progressive loss of anticoagulant activity with globulin in 0.9% saline, of a loss of metachromatic activity after phenol extraction and the reversal of the latter by alkali. The latter observations were due to the solubility in phenol of heparin on combination with protein. With suitable preparations, a decrease in anticoagulant activity without decrease in metachromatic activity was observed, i.e. conversion of heparin to uroheparin. Loss of heparin due to combination with protein and resulting precipitation, solubility in phenol, etc. followed a protein pH-dissociation curve. Loss of heparin anticoagulant activity due to heparinase was maximal at pH 5.4. No loss of heparin occurred at pH values more acid than 5 or more alkaline than 7.

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