Preferential consumption of heparin cofactor II in disseminated intravascular coagulation associated with acute promyelocytic leukemia.

We measured plasma heparin cofactor II (HC II) activity in patients with disseminated intravascular coagulation (DIC) due to various underlying diseases together with the levels of antithrombin III (AT III), pseudocholinesterase (a marker of hepatic synthesis), and various haemostatic molecular markers. Both HC II and AT III were decreased in DIC secondary to all the underlying diseases studied, except acute promyelocytic leukemia (APL), when compared with healthy subjects. The lowest HC II and AT III levels was observed in coagulopathy secondary to liver disease, the HC II level in sepsis was the second lowest. In DIC due to APL, the decrease in HC II was not accompanied by a decrease in AT III. Thus, we divided all 124 samples tested into APL and non-APL groups. The HC II level correlated positively with fibrinogen and plasminogen in both the APL and non-APL groups. In the APL group, the HC II level had a significant negative correlation with the thrombin-AT III complex (TAT), fibrinogen/fibrin degradation products, and D-dimer levels as well as the prothrombin time, while AT III showed no correlations with any of the haemostatic parameters. These results suggest that HC II may be consumed preferentially by thrombin in APL patients with DIC, and thus may spare the consumption of AT III. Accordingly, HC II seems to be a superior indicator of DIC than AT III in APL patients. Moreover, replacement therapy with HC II instead of AT III may be useful to treat DIC associated with APL. In the non-APL group, the HC II levels were positively correlated with the levels of AT III and pseudocholinesterase activity. This indicates that plasma HC II levels are closely related not only to consumption coagulopathy but also to hepatic synthetic activity, as is the case for plasma AT III.     

Antithrombin III and heparin cofactor II in patients with chronic renal failure undergoing regular hemodialysis

Heparin enhances the inhibition rate of thrombin by both antithrombin III (AT III) and heparin cofactor II (HC II). We studied the activity of these two plasma proteins in patients with chronic renal failure (CRF) undergoing regular hemodialysis as their heparin requirements varied widely. In 77 normal blood donors, normal ranges (mean +/- 2 SD) were 82-122% for AT III and 65-145% for HC II. When compared with these controls 82 dialyzed CRF patients had a subnormal AT III activity and a significantly (p less than 0.001) lower HC II activity. To evaluate the effect of hemodialysis we compared AT III, HC II and total proteins in plasma before and after dialysis in 24 patients (12 with normal and 12 with low basal HC II activity). AT III and HC II activities significantly (p less than 0.001) increased in absolute value. When related to total plasma proteins, in order to suppress the influence of hemoconcentration induced by dialysis, AT III decreased significantly (p less than 0.01) whereas HC II increased slightly but significantly (p less than 0.01) in the 12 patients with low initial HC II activity. The decrease of AT III induced by heparin administrated during dialysis is likely to account for this relative decrease of AT III activity. A modification of the distribution of both HC II and heparin between the vascular wall and the circulating blood is evoked to explain the relative increase in HC II activity and the need for higher heparin dosage in patients with low HC II levels.     

Plasma and urinary heparin cofactor II levels in patients with nephrotic syndrome

Heparin cofactor II (HC II) levels were measured by electroimmunoassay in plasmas and urines from 68 patients with nephrotic syndrome. In addition, antithrombin III (AT III) and protein C (PC) activities and antigens were measured also in the same group of patients. Seven of these patients had histories of thrombosis. Plasma HC II levels (mean +/- SD 105 +/- 43) were not different from levels in healthy subjects (94 +/- 17). Only 5 patients had low plasma levels of HC II. None of the patients with thrombosis had low HC II levels. Even though measurable amounts of HC II were found in 25 urines from 50 patients. There was a relationship in the urinary excretion between HC II and AT III and their urinary clearances were quite similar. However, no correlation was found between plasma HC II and AT III levels, and levels of AT III activity and antigen were significantly lower than in healthy subjects. Three patients with histories of thrombosis had low AT III levels. Most patients (including those with thrombosis histories) had high plasma PC levels and increased urinary loss. It is suggested that HC II does not play an important role in the pathogenesis of thrombosis in nephrotic syndrome.     

Heparin cofactor II inhibits thrombin-stimulated release of tissue plasminogen activator from cultured human endothelial cells in the presence of dermatan sulfate

To investigate the involvement of heparin cofactor II (HC II) in fibrinolytic system, endothelial cells from human umbilical vein were cultured in the presence of HC II or antithrombin III (AT III) combined with or without thrombin. Although AT III significantly inhibited thrombin-induced increase in tissue plasminogen activator antigen (t-PA:Ag) release, HC II did not exhibit such a suppressive effect. In contrast, in the presence of dermatan sulfate, HC II inhibited thrombin stimulation of t-PA:Ag release more strongly than AT III did. The release of plasminogen activator inhibitor-1 antigen (PAI-1:Ag) was also stimulated by thrombin; this stimulation was inhibited only by the combination of HC II and dermatan sulfate. Comparatively high concentrations of HC II significantly suppressed thrombin stimulation of t-PA:Ag and PAI-1:Ag release but did not cause an obvious change of both release in the absence of thrombin. Based on these results, it was suggested that HC II may inhibit an increase in fibrinolytic activity mediated by thrombin-stimulated endothelial cells in the liquid phase through a suppression of thrombin stimulation of t-PA:Ag release, when plasma is exposed to vascular smooth muscle cells or fibroblasts which synthesize a significant amount of dermatan sulfate.     

Use of purified dermatan sulfate for heparin cofactor II (HC II) assay.

HC II functional assays are generally preferred with respect to immunochemical assays. Nevertheless functional assays can be biased by the antithrombin III (AT III)-heparin complex activity; in fact trace amounts of heparin generally contaminate dermatan sulfate (DS) commercial preparations used as HC II reaction activators. We have employed a purified DS preparation showing these features: DS concentration 94.4%, chondroitin sulfate 5.6%, M.W. 21.4 kDa. The absence of any interference due to AT III-heparin complexes was verified in a kinetic HC II assay of some human plasma pools. The immunological inhibition of AT III by anti-AT III caused a minimal decrease (6-8%) of the reaction slope, attributable to AT III activity. Progressive increase of heparin concentration in the assay was effective only starting from 30 U/ml (the assay was carried out in the presence of polybrene to prevent any AT III activation). The reference interval (mean +/- SD) obtained from 157 normal subjects was 100.8 +/- 20.2%; there was a good correlation with immunoreactive HC II. The purified DS we have used seems suitable for routinary assays of HC II where a minimal interference due to AT III-heparin is required.     

Heparin cofactor II deficiency in renal allograft recipients: no correlation with the development of thrombosis

Heparin cofactor II (HC II) is a thrombin inhibitor in human plasma which displays great similarities with antithrombin III (AT III). Hereditary HC II deficiency was recently reported to be associated with thrombophilia. Since thromboembolism constitutes an important post-operative complication after renal transplantation, we measured HC II and AT III in the plasma of 118 healthy renal allograft recipients (RAR) and found stable low HC II and high AT III levels. Administration of azathioprine (AZA), cyclosporine A (CSA) or both as immunosuppressive therapy did not affect HC II levels, but CSA seems to have raised plasma AT III. The proportion of patients with HC II deficiency was significantly higher in RAR than the proportion we previously found (11) in healthy individuals (16.9% vs 1.5%). However, the proportions with low plasma HC II were not different in healthy RAR and in ten RAR with thrombotic events, suggesting that in transplanted patients, HC II deficiency is not in itself a risk factor for the development of thrombosis.     

Measurement of markers of activated coagulation in antithrombin III deficient subjects.

Functional antithrombin III levels were measured by factor Xa inhibition in 63 members of a large family with type 2 antithrombin III deficiency and individuals were classified as antithrombin III deficient or non-deficient according to the results. F1 + 2 and TAT complexes were measured using an ELISA and FPA levels were measured by radioimmunoassay. Thirty subjects (48%) were classified as antithrombin III deficient and 33 (52%) as antithrombin III non-deficient. The mean level of F1 + 2 was significantly higher in the deficient adults (0.87 +/- 0.26) compared to both the non-deficient adults (0.70 +/- 0.21) (p = 0.03) and the deficient adults receiving warfarin (0.16 +/- 0.01) (p less than 0.001). The differences in the mean values of TAT complexes and FPA between deficient and non-deficient individuals were not statistically significant. These findings suggest that untreated antithrombin III deficient subjects generate more thrombin than their non-deficient family members and that warfarin inhibits this thrombin formation. In this cross-sectional study, it is not possible to correlate the levels of the surrogate makers with future clinical outcome.     

Purification and biological property of heparin cofactor II: Activation of heparin cofactor II and antithrombin III by dextran sulfate and various glycosaminoglycans

Heparin cofactor II (HC II) has been purified from human plasma by a mocification of the method described by Tollefsen $\text{et al}$.(J. Biol. Chem., $\text{257}$, 2162, 1982) and abilities of dextran sulfate and various glycosaminoglycans to activate the antithrombin activities of HC II and antithrombin III (AT III) were studied. By the purification method described here, highly purified HC II with the same specific activity as reported by Tollefsen $\text{et al}$. was obtained with a higher yield and in a shorter purification time. Heparin, dextran sulfate and chondroitin polysulfates 1 and 5 activated both HC II and AT III, while dermatan sulfate activated only HC II. Dextran sulfate was almost as active as heparin in the activation of HC II and AT III, indicating that in the interactions of heparin with HC II and AT III, sulfate groups of heparin are more important than carboxyl groups. When mixed with thrombin in the presence of dermatan sulfate, normal human plasma showed antithrombin activity which was not due to AT III but to HC II only. HC II did not inhibit factor Xa or plasmin in the presence of any glycosaminoglycans or dextran sulfate, suggesting that HC II would be a specific inhibitor of thrombin.     

Heparin response and clearance in acute and chronic liver disease

Patients with liver disease are at risk of bleeding due to abnormalities of the clotting system although they must be anticoagulated if they require haemodialysis or haemoperfusion. The anticoagulant of choice is heparin. In this study we have investigated heparin kinetics in patients with fulminant hepatic failure (FHF) after a single intravenous dose of heparin (2,500 units) and found there was an increased clearance of heparin whether measured by its anti-Xa effect (t 1/2 = 27.8 +/- 2.9 min compared to t 1/2 = 50.2 +/- 2.7 min in normal controls p less than 0.001) or by the whole blood activated clotting time (t 1/2 = 23.7 +/- 2.2 min compared to t 1/2 = 37.0 +/- 2.0 min p less than 0.001). There was a decreased peak level of heparin measured by anti-Xa effect (peak level in FHF = 0.48 +/- 0.05 u/ml and in controls = 0.69 +/- 0.04 u/ml, p less than 0.02), but an increased sensitivity to heparin (sensitivity in FHF = 0.072 +/- 0.011 sec/unit, in controls 0.033 +/- 0.003 sec/unit, p less than 0.001). Patients with FHF had very low levels of antithrombin III (AT III), but there was no correlation between this and any parameters of heparin effect or clearance. In a group of patients with chronic liver disease heparin kinetics did not differ from controls despite low levels of AT III. The changes in heparin kinetics in FHF are likely to be complex with the balance between the proteins that act as cofactors, (e.g. AT III) and the proteins that have heparin neutralising activity, controlling the response of added heparin.     

Fibrinolysis and coagulation in patients with infectious disease and sepsis

Sepsis is often associated with hemostatic dysfunction. This study aimed to relate changes in fibrinolysis and coagulation parameters to sepsis and sepsis outcome. Urokinase-type plasminogen activator (u-PA) antigen, tissue-type plasminogen activator (t-PA) antigen and activity, plasminogen activator inhibitor (PAI) type 1 antigen, PAI activity, antithrombin (AT) III activity, and protein C activity were measured in 24 patients suffering from sepsis or septic shock and the results were compared with those observed in 30 non-sepsis patients with severe infectious disease. The u-PA level was markedly increased in plasma of sepsis patients as compared to non-sepsis patients (11.5 +/- 9.4 versus 1.6 +/- 1.5 ng/ml, p less than 0.0001). PAI-1 antigen and t-PA activity showed a significant increase in sepsis patients (320 +/- 390 ng/ml versus 120 +/- 200 ng/ml, and 3.0 +/- 3.6 IU/ml versus 1.0 +/- 0.7 IU/ml, respectively, p less than 0.01). AT III was decreased in sepsis patients (58 +/- 28% in sepsis versus 79 +/- 26% in severe infectious disease, p less than 0.01) as was protein C (30 +/- 18% versus 58 +/- 27%, p less than 0.001). No significant difference was found for t-PA antigen nor for PAI activity. Nonsurvivors of sepsis were distinguished mainly by a high u-PA antigen level and increased t-PA activity. It is concluded that plasma u-PA antigen showed the strongest significant difference, among the parameters evaluated, between sepsis and severe infection. u-PA antigen may be of prognostic value in patients admitted to the medical intensive care unit for severe infectious disease.     

Antithrombin III in renal transplant recipients

Antithrombin III (AT III) is increased in situations where there is increased platelet turnover. Plasma AT III levels measured in 39 renal transplant recipients were significantly higher than in 20 healthy subjects (p less than 0.001) and 20 patient controls (p less than 0.025). AT III levels were significantly correlated with the patients' platelet counts (r = 0.4, p less than 0.02). Transplant patients with less than 1 year follow up had significantly higher AT III levels than patients with more than 1 year follow up (p less than 0.01). All 5 patients with transplant rejection in the study had elevated plasma AT III levels. The data suggest that elevation of plasma AT III may be related to graft rejection.     

Carbamazepine/valproic acid interaction in man and rhesus monkey

Sodium valproate (VPA) was administered for 1 week (1 g b.i.d.) to seven epileptic patients receiving chronic carbamazepine (CBZ) therapy. Steady-state CBZ levels determined before and after VPA therapy were reduced by 3-59% in six patients and were unchanged in one patient. The plasma concentration ratio of carbamazepine-10,11-epoxide ( CBZE ) to CBZ increased in all patients by 11-500%. The plasma binding of CBZ was determined in six healthy volunteers given a single 400 mg CBZ dose with and without the coadministration of 1 g VPA in a cross-over design. The mean CBZ free-fraction was increased in three of the subjects (p = 0.008-0.031), decreased in one subject (p less than 0.002), and remained unchanged in two subjects when VPA was administered. Four male rhesus monkeys were infused intravenously with CBZ (15 mg h-1) for 5 days and then three consecutive 24-h infusions were given: I, CBZ alone; II, CBZ with 75 mg h-1 VPA; III, CBZ with 150 mg h-1 VPA. The mean free-fraction of CBZ and CBZE increased during infusions II and III from 31.5 +/- 2.7% to 33.6 +/- 2.6% (p less than 0.05) and 37.7 +/- 1.3% (p less than 0.01) for CBZ and from 46.9 +/- 9.2% to 53.6 +/- 5.7% (p greater than 0.05) and 60.1 +/- 4.0% (p less than 0.01) for CBZE . The clearance of free CBZ declined from 7.96 +/- 1.75 to 4.84 +/- 1.26 (p less than 0.01) and 4.12 +/- 1.75 (p less than 0.01) 1 kg-1h-1 during infusions II and III, respectively. The mean free CBZE /CBZ ratio increased from 0.12 +/- 0.03 to 0.24 +/- 0.03 and 0.36 +/- 0.04 during infusions II and III, respectively (p less than 0.001). These findings indicate a decrease in the elimination clearance of CBZE possibly coupled with a decrease in its formation clearance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Turnover study of heparin cofactor II in healthy man

Heparin cofactor II (HC II) is a heparin-dependent inhibitor of thrombin, distinct from antithrombin III (AT III). This study was designed to evaluate its metabolism in healthy subjects. Purified HC II was labelled with 125I by the lactoperoxidase-glucose oxidase technique. The biological activity of the HC II was unchanged after labelling as was its migratory pattern by crossed immunoelectrophoresis in the presence of heparin or dermatan sulfate. Three healthy volunteers were injected with 10 microCi and the plasma radioactivity was measured daily. The data were approximated by a sum of two exponential terms and the metabolism of HC II was described by a two compartment mamillary system. The mean values of fractional catabolic rate, intravascular fraction and half-life of the elimination phase were respectively: 0.44 d-1, 0.60 and 2.53 d. These parameters are of the same order of magnitude as those reported in the literature for AT III. The plasma HC II concentration in the 3 subjects ranged from 61 to 82 micrograms/ml as estimated using our purified preparation. Accordingly, the absolute catabolic rate ranged from 1.17 to 1.36 mg X kg-1 X d-1.     

Homozygous variant of antithrombin III that lacks affinity for heparin, AT III Kumamoto

Abnormal antithrombin III (AT III) was found in the plasma of a 31-year-old female who suffered from recurrent thrombotic episodes. Heparin cofactor activity was 28% of normal and undetectable when measured by inhibition of thrombin and factor Xa (F.Xa), while both progressive antithrombin and antifactor Xa activities were normal. The concentration of plasma AT III antigen was 37 mg/dl. Analysis by crossed-immunoelectrophoresis (CIE) in the presence of heparin and affinity chromatography on heparin-Sepharose revealed that the propositus' AT III did not bind to heparin. When heparin cofactor II (HC II) was removed from propositus' plasma, heparin cofactor activity of AT III was not detected. Thus, HC II seemed to account for the plasma heparin cofactor activity found in the presence of thrombin. The patient's parents and three of her brothers demonstrated qualitative abnormality of AT III; heparin cofactor activity was 30-50% of normal levels in the presence of both thrombin and F.Xa. These findings indicate that the propositus' AT III lacks affinity for heparin and the mode of its inheritance seems to be autosomal dominant and, hence, the propositus would be a homozygote. For this variant, the name of AT III Kumamoto is proposed.     

No evidence for short-term regulation of plasminogen activator inhibitor activity by insulin in man.

In cross-sectional studies a positive correlation has been found between circulating insulin, triglycerides and plasminogen activator inhibitor (PAI-1) activity. To directly examine the effect of insulin on PAI-1 activity in vivo, we determined the response of PAI-1 activity in 17 normal subjects to acute hyperinsulinemia (serum free insulin 92 +/- 8 mU/l) during maintenance of normoglycemia (plasma glucose 5.1 +/- 0.1 mmol/l). In 12 matched control subjects PAI-1 activity was measured during infusion of saline (serum free insulin 3.6 +/- 0.3 mU/l, plasma glucose 5.2 +/- 0.1 mmol/l). Plasma PAI-1 activity decreased during the insulin infusion from 9.0 +/- 1.4 to 5.6 +/- 0.8 U/ml (p less than 0.01), and during saline infusion from 7.0 +/- 1.4 to 4.3 +/- 0.6 U/ml (p less than 0.05). Serum triglyceride concentrations decreased from 1.09 +/- 0.20 to 0.76 +/- 0.09 mmol/l (p less than 0.001) during hyperinsulinemia but remained unchanged during the saline infusion (1.04 +/- 0.11 vs. 1.02 +/- 0.12 mmol/l, NS). We conclude that insulin does not acutely change plasma PAI-1 activity, and that acute insulin-induced changes in serum triglycerides occur independently from those of PAI-1 activity.     

Which factors affect high D-dimer levels in the elderly?

To study the age-related changes in plasma D-dimer levels and the effect of atherosclerotic disease and long-term immobilization on haemostasis the elderly, we measured plasma D-dimer levels in 148 subjects aged from 60 to 94 years using an ELISA. We also measured plasma fibrinogen, serum uric acid, total cholesterol, triglycerides, HDL cholesterol, beta-lipoprotein fractions, and apolipoproteins (A-I, A-II, B, E). Plasma D-dimer levels (326 +/- 148 ng/ml) were significantly higher in the healthy elderly subjects than in younger controls (180 +/- 58 ng/ml, p less than 0.01) and increased further with age (r = 0.344, p less than 0.01). D-dimer levels were significantly higher in elderly women than in elderly men (p less than 0.05). The D-dimer level correlated significantly with both the fibrinogen antigen level (r = 0.286, p less than 0.001) and the clotting activity (r = 0.275, p less than 0.01), and also correlated with apolipoprotein E levels. There were no correlations with the other parameters assessed. The D-dimer levels were significantly higher in the elderly subjects with atherosclerotic disease (516 +/- 285 ng/ml) than in healthy elderly subjects (p less than 0.001). Moreover, the levels were even higher in elderly subjects with long-term immobilization (866 +/- 408 ng/ml) than in subjects with atherosclerosis, even after age, sex and underlying diseases were taken into consideration. These results indicate that coagulation and fibrinolysis activity are increased in the elderly, especially those with atherosclerotic disease and that moreover long-term immobilization further accelerates their haemostatic hyperactivity.     

Antithrombin activity of a fucan sulfate from the brown seaweed Ecklonia kurome

The mechanism of antithrombin action of a fucan sulfate (C-II), which was isolated from the brown seaweed Ecklonia kurome, was examined by clotting method using a thrombin-fibrinogen system and by amidolytic method using a chromogenic substrate in the presence and the absence of antithrombin III (AT III) or heparin cofactor II (HG II). C-II significantly inhibited the clotting of fibrinogen by thrombin even in the absence of the protease inhibitors, and the anidolytic activity of the protein only in the presence of HC III. C-III was not adsorbed on an AT III-agarose column and its anticoagulant activity in AT III-depleted plasma was the same as that in normal one. Examination of interaction of C-III with fibrinogen by g-el filtration chromatography demonstrated that C-III bound to the protein. These results indicated that the antithrombin activity of C-III was mediated by HC III and not by AT III, and that the polysaceharide bound to fibrinogen, thereby blocking thrombin action, and also that its direct thrombin inhibition was very weak.     

Heparin cofactor II: a simple assay method and results of its clinical application

A simple assay method of heparin cofactor II (HC II) activity is described. The procedure is based on the following principle: Antithrombin III (AT III) in plasma is inactivated by addition of an IgG fraction of goat serum after immunization of the animals against human AT III. Complete inactivation of AT III could be shown by absence of an anti Xa-effect of heparinized plasma treated with this antibody. Thrombin was only partially inhibited after inactivation of AT III. The characteristics of this inhibition were typical for the action of HC II. This method was applied for an assay of HC II activity. After optimizing of the method practical application in clinical routine screening was carried out. A diminution of HC II was observed in liver cirrhosis and in DIC but not in AT III deficiency. In 15 out of 269 cases of recurrent DVT there were HC II activities below 70% of normal. In 4 out of these patients activities of HC II were repeatedly between 44% and 52%. In arterial obstructive disease there was an HC II activity of less than 60% in 18 out of 583 patients and in 11 of them the HC II levels were repeatedly between 45% and 54%.     

The predictive value of the hemostasis parameters in the development of preeclampsia.

In order to find out which hemostasis parameters would have the predictive value for the development of preeclampsia, modified antithrombin III (ATM, representative of the antithrombin III-serine esterase complex), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), beta-thromboglobulin (BTG), antithrombin III (AT III), fibrinogen, fibrin(ogen) degradation product (FDP), FDP D-dimer and euglobulin lysis time (ELT) were measured in 20 normal non-pregnant women, 21 normal pregnant women, 6 high-risk pregnant women, 14 preeclampsia pregnant women, and 5 patients with disseminated intravascular coagulation (DIC). Only tPA and AT III were found significantly different between the preeclampsia and the normal or high-risk pregnant women: tPA was found progressively and significantly increased from the normal pregnant, to the high-risk pregnant, then to the preeclampsia women (p less than 0.05). AT III was significantly lower in the preeclampsia than in the normal pregnant (p = 0.0001) or in the high-risk pregnant women (p = 0.002). In the 2nd trimester, tPA, PAI, fibrinogen and FDP were significantly higher, and AT III was significantly lower in the preeclampsia than in the normal pregnant women, whereas in the 3rd trimester, tPA and AT III were significantly higher or lower, respectively, in the preeclampsia than in the normal pregnant women. No significant difference of ATM could be found between the preeclampsia and the normal or high-risk pregnant women. From the present study, we suggest that tPA and AT III would be used as the main predictors, and FDP and D-dimer as the complementary predictors for the development of preeclampsia and should be detected in the normal or high-risk pregnant women.     

Comparative turn-over of heparin cofactor II and antithrombin III in baboons. Influence of heparin and pentosan polysulfate administration

Heparin and pentosan polysulfate (PPS) interact in plasma with antithrombin III (AT III) and Heparin cofactor II (HC II) respectively. To assess the influence of heparin or PPS treatment on the metabolism of their respective cofactors, we performed a double tracer study in baboons receiving heparin or PPS. Purified AT III and HC II from human plasma were labelled with 131I and 125I respectively by the lactoperoxidase-glucose oxidase technique. The tracers had unchanged biological activities, were homogeneous in SDS-PAGE, migrated as native proteins by crossed immunoelectrophoresis in the presence of heparin or PPS and virtually coeluted with endogenous baboon proteins from heparin-agarose. Nine animals were randomly allocated to receive, during the metabolic study, heparin (500 IU/kg/d, n = 3), PPS (5 mg/kg,d, n = 3) or a placebo (n = 3) given in 2 daily subcutaneous injections. Heparin levels and anticoagulant effects were similar in extent and duration to those usually achieved in man. The plasma concentrations of AT III and HC II did not vary under treatment. The half-life of the elimination phase in the placebo group ranged from 1.95 to 2.33 d for AT III and from 1.96 to 2.21 d for HC II. There was no significant difference in the half-lives of the 2 inhibitors between the placebo group and the animals receiving heparin or PPS. This suggest that clinical conditions associated with heparin treatment may be important for the effect of heparin on AT III metabolism previously reported in patients.(ABSTRACT TRUNCATED AT 250 WORDS)