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A comparative study of venous occlusion and ddavp stimulated fibrinolysis in normolipidemic subjects
THROMBOSIS RESEARCH 52; 655-660, 1988 0049-3848/88 $3.00 t .OO Printed in the USA. Copyright (c) 1988 Pergamon Press plc. All rights reserved.
BRIEF
COMMUNICATION
A COMPARATIVE STUDY OF VENOUS OCCLUSION AND DDAVP STIMULATED FIBRINOLYSIS IN NORMOLIPIDEMIC SUBJECTS
P. Smith*, H. Arnesen", K.H. Dahl**, D.W.T. Nilsen*, T. Opstad* and P. Andersen" *Red Cross Clinic and **Hemostasis Research Section, Nycomed A/S, Oslo, Norway. (Received 3.5.1988; accepted in revised form 10.8.1988 by Editor H.C. Godal) (Received in final form by Executive Editorial Office 12.10.1988) INTRODUCTION Stimulized release of the vascular plasminogen activator (t-PA) may be brought about by venous occlusion (VO) (1) or may be induced pharmacologically by the vasopressin-analogue DDAVP (1-Desamino-8-D-Arginine Vaso-pressin) (2). The fibrinolytic response to either one of these stimuli may be evaluated in clot lysis systems such as the euglobulin clot lysis time (ECLT)(3), and in assays using chromogenic substrates (4,5). In subjects with hypertriglyceridemia, reduced fibrinolytic response following both VO (6) and DDAVP (7) has been noted. Furthermore, hypertriglyceridemit subjects who are non-responders to venous occlusion in terms of the ECLT, may be responders to DDAVP (8). Previous studies comparing DDAVP and VO in normals are small and do not provide information on lipoprotein levels in the tested subjects (9-11). In the present study we have investigated single fibrinolytic variables and ECLT following stimulation by VO and DDAVP in 21 healthy normotriglyceridemic volunteers. SUBJECTS AND METHODS Subiects The study population comprised 21 healthy volunteers, 12 males and 9 females. Mean age was 40 years (range 21 - 51) and mean Body Mass Index was 22.1 kg/m2 (range 18.4-28.0). None of the subjects had a history of thromboembolic disease, none were taking any drugs and none of the women were taking oral contraceptives. Testing Procedures All tests were performed in the fasting condition between 8 and 10 a.m. Before ----~---~~~-~~~~~-~~~~~~~~~~~ Key words: Venous occlusion, DDAVP, fibrinolysis. 655
656
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Vol. 52, No. 6
stasis, blood was collected for determination of plasminogen activator inhibitor (PAI), triglycerides and baseline t-PA. Venous stasis was applied to the upper arm with a sphygmomanometer cuff of 90 mm Hg for 20 minutes (1). Blood samples for determination of fibrinolytic capacity by the ECLT and t-PA measurements were collected from an antecubital vein of the occluded arm just prior to release of the stasis. After a resting period of 30 minutes, DDAVP (Minirino, Ferring, Maims, Sweden)(0,4pg/kg body weight) was injected over 10 minutes in the arm that had been exposed to venous occlusion. Blood samples were drawn from the contralateral arm 30 minutes later. Analytical Methods Euglobulin fibrinolytic activity was determined in terms of ECLT, mainly as described by Nilsson (3). Results are expressed in minutes (normal 6 45) (12). Acidified plasma was prepared immediately by adding one part 1 M Na-acetate buffer, pH 3.9, to two parts of citrate blood. After centrifugation the plasma was snap-frozen in liquid nitrogen and stored at -7OoC. Specific t-PA activity was determined amidolytically with a chromogenic substrate (PL-l,H-D-Nleu-CHALys-pNA, Nycomed, Oslo, Norway) mainly as described by Wiman (4). The t-PA standard was prepared from melanoma cell cultures as described by Radcliffe et al (13) and calibrated against the international t-PA standard 83/517. Poly-Dlysine (Sigma, St. Louis, U.S.A.) was used as promoter. t-PA antigen (t-PA:Ag) was assayed by an ELISA method using a commercially available kit (Imulyse, Biopool, Umed, Sweden) (5). Values for t-PA activity are expressed as units/ml (U/ml), whereas t-PA:Ag values were estimated as nanogram/ml (ng/ml). One ng t-PA = 0.5 U. The fast acting t-PA inhibitory activity (PAI) was measured amidolytically according to Chmielewska et al (14) and is given as units (U/ml), 1 inhibitor unit being defined as the amount required to neutralize 1 unit t-PA (Spectrolyse, Biopool, Sweden). Mean PA1 level in the reference population of our laboratory was 7*4 (SD). Blood lipids were determined enzymatically by conventional methods (Boehringer Mannheim GmbH, FRG). Statistical Methods Wilcoxon's sign rank test was applied for comparison of data before and after stimulated release of t-PA. The association between variables was measured by the Spearman rank correlation coefficient. A p-value of <0.05 (two-tailed) was considered statistically significant. Group data are reported as medians unless otherwise indicated.
RESULTS Lipids, PA1 and ECLT Triglycerides, total cholesterol and HDL-cholesterol were all within normal limits of our laboratory. PA1 before stimulation revealed values within normal limits (median 1.6 U/L, range O-6). The median value of ECLT following DDAVP was shorter (20 minutes, range 13-40) than that post stasis (30 minutes, range 10-110) (p=O.O25) (fig.1). Four cases exceeded the upper normal limit of 45 minutes (range 55-110) as judged by ECLT after VO, but not so after DDAVP. t-PA and t-PA:Ag Due to hemolysis, determination of t-PA activity was not done in one sample. Median t-PA activity at baseline was 0.2 U/ml (range O-0.9) and t-PA:Ag was 4.3 ng/ml (range l-6.0). There was a statistically highly significant increase
Vol. 52, No. 6
STIMULATED FIBRINOLYSIS
657
of plasma t-PA (antigen and activity) (p
1
U/ml
I.5 6-
30 30
I
4.8
4_
min.
20
2-
Jl 2.2
1.1
0.2
P
t-PA t-PA:Ag BASELINE
0.7 CT:
;
r t-PA
t-PA&A:""
t-PA:Ag vo
-
;
ooAEVCPLT v”
FIG. 1 Median t-PA activity and t-PA antigen (converted to units) before and after DDAVP and VO. Median ECLT (minutes) after DDAVP and VO (right axis). Bars on top of column = 1 SEM.
The four subjects with abnormal ECLT after VO had t-PA activity readings that were distictively lower than after DDAVP (Fig 2). A similar pattern was seen regarding t-PA:Ag measurements.
L t-PA (VO) t-PA (DDAVP)
v
t-PA:Ag (VO) t-PA:Ag (DDAvP) w FIG. 2 Ranked values of t-PA response in terms of t-PA activity and t-PA antigen. Low (L) and high (H) end of array respectively. 0 Denotes normals and ??denotes low responders in terms of ECLT after VO. Correlations The ECLT after VO and DDAVP, respectively, were only weakly correlated (r==0.3, p = 0.11). t-PA activity following the two procedures were well correlated,
658
however between
STIMULATED FIBRINOLYSIS
Vol. 52, No. 6
(r=0.51, p=O.O2). There was no statistical significant correlation t-PA:Ag following the same stimuli (r=0.19, p=O.42).
DISCUSSION A brisker fibrinolytic response in terms of ECLT has been found following DDAVP compared with VO in hypertriglyceridemic subjects (8). Some studies have addressed the same issue in assumed normals (9-11). However, only small numbers of persons have been investigated, and the lipoprotein profile has not been documented. As in hypertriglyceridemics, the subjects in our study were throughout less responsive to VO than to DDAVP in terms of ECLT readings. The weaker responsiveness occurred despite higher levels of t-PA after VO, both when expressed in terms of functional t-PA and as t-PA antigen (fig.1). Our data thus confirm the results of Prowse et al. (9), who compared the hemostatic responses to DDAVP, VO and exercise in 6 male volunteers. In that study euglobulin clot lysis time showed higher fibrinolytic activity after DDAVP-infusion than after VO, whereas t-PA:Ag revealed the opposite pattern. Different results have been obtained by others, however. In a study in 7 normal persons Nilsson et al. found roughly the same responses in terms of fibrinolytic activity following both DDAVP and VO (10). Another paper reporting on effects of DDAVP in patients with panhypopituitarism found both higher t-PA:Ag and euglobulin fibrinolytic activity after DDAVP than following VO in a control group of 6 subjects (11). In the latter study the stimulation tests were performed with an interval of 15 days, and venous occlusion was applied for 10 minutes. The hemoconcentration inevitably occurring during VO may have influenced the concentration of t-PA after this procedure. No correction has been made for such changes. However, the magnitude of changes likely to occur (9), should not have influenced the readings significantly. Fibrinolytic activity following VO is a useful predictor in prethrombotic and thrombotic states (7,15,16). Weak responders to DDAVP have been described in familial thromboembolism (17) and in spontaneous thrombosis (18). Four subjects had abnormal ECLT readings after VO despite normal values following DDAVP. Fig. 2 suggests that at least in some of the cases this may have been brought about by less released t-PA after VO. However, the possibility of different release of PA1 by the two stimulation procedures should be kept in mind. In conclusion, our study has confirmed diversities between response to VO and DDAVP in normolipidemic subjects. Hence, these procedures may not always be compatible. Future studies aiming at elucidating the mechanisms involved should include also determination of PA1 (activity as well as total amount) before and after stimulation. Such studies should additionally take into account the possibility of the two stimuli acting differently on release of t-PA and PA1 from non-endothelial sources. REFERENCES 1. ROBERTSON BR, PANDOLFI M, NILSSON IM. Fibrinolytic capacity in healthy volunteers as estimated from effect of venous occlusion of arms. Acta Chir. Stand. 138,429-36,1972. 2. GADER AMA, da COSTA J, CASH JD.L-desamino-8-d-arginine vasopressin and fibrinolysis in man. Scot. Med. J. 19,56-7,1974
Vol. 52, No. 6
STIMULATED FIBRINOLYSIS
3. NILSSON IM, OLOW B. Fibrinolysis Chir. Stand. 123,247-66,1962.
induced by
streptokinase in
659
man. Acta
4. WIMAN B, MELLBRING G, RANBY M. Plasminogen activator release during venous stasis and exercise as determined by a new specific assay. Clin. Chim, Acta 127,279-88,1983. 5. BERGSDORF N, NILSSON T, WALLEN P. An enzyme linked immunosorbent assay for determination of tissue plasminogen activator applied to patients with thromboembolic disease. Thromb. Haemostas. 50,740-4,1983. 6. ANDERSEN P, ARNESEN H, HJERMANN I. Hyperlipoproteinemia and reduced fibrinolytic activity in healthy coronary highrisk men. Acta Med. Stand. 209, 199-202,1981. 7. BROMMER EJP, BARRET-BERGSHOEFF MM, ALLEN RA, SCHICHT I, BERTINA RM, SCHALEKAMP MADH. The use of desmopressin acetat as a test of the fibrinolytic capacity of patients - analysis of responders and non-responders. Thromb. Haemostas. 48(2),156-61,1982. 8. NILSEN DWT, ANDERSEN P, HJERMANN I, GODAL HC. Discrepancy in fibrinolytic response to desmopressin as compared to venous occlusion. Thromb. Haemostas. 53,60,1985. 9. PROWSE CV, FARRUGIA A, BOULTON FE, TUCKER J, LUDLAM CA, McLAREN M, BELCH JJF, PRENTICE CRM, DAWES J, MacGREGOR IR. A comparative study using immunological and biological assays of the haemostatic responses to DDAVP infusion, venous occlusion and exercise in normal men. Thromb. Haemostas. 51,110-4,1984. lo. NILSSON IM, VILHARDT H, HOLMBERG L, ASTEDT B. Association between factor VIII related antigen and plasminogen activator. Acta Med. Stand. 211,10512,1982. 11. JUHAN-VAGUE 1, CONTE-DELVOX B, AILLAUD MF, MENDEZ C, OLIVER C, COLLEN D. Effects of DDAVP and venous occlusion on the release of tissue-type plasminogen activator and von Willebrand factor in patients with panhypopituitarism. Thrombosis Res. 33,653-9,1984. 12. NORDBY E, ARNESEN H, ANDERSEN P, GODAL HC. The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis. Stand. J. Haematol. 25,407-11,198O. 13. RADCLIFFE R, HEINZE T. Isolation of plasminogen activator from human plasma by chromatography on Lysine-sepharose. Arch. Biochem. Biophys. 189, 185-94,1978. 14. CHMIELEWSKA J, RANBY M, WIMAN B. Evidence for a rapid inhibitor to tissue plasminogen activator in plasma. Thrombosis Res. 31,427-36,1983. 15. ISACSON S, NILSSON IM. Defective fibrinolysis in blood and vein walls in recurrent "idiopathic" venous thrombosis.Acta Chir. Scand.138,313-19,1972. 16. ARNESEN H, SEMB G, HOL R, KARLSEN H. Fibrinolytic capacity after venous stasis in patients undergoing aortocoronary by-pass surgery. Relation to shunt occlusion. Stand. J. u. 30 (supp1),43-6,1983.
660
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Vol. 52, No. 6
17. JOHANSSON L, HEDNER U, NILSSON IM. A family with thromboembolic disease associated with deficient fibrinolytic activity in vessel wall. Acta Med. Stand. 203,477-80,1978. 18. ABERG M, NILSSON IM, VILHARDT H. The release of fibrinolytic activator and factor VIII after injection of DDAVP. In: Progress in chemical fibrinolysSamama MM Desnoyers PC is and thrombolysis, Davidson JF, Cepelak V 5. Edinburgh-London-New York: Churchill Livfngstone, 19+9, pp 92-7.
BRIEF
COMMUNICATION
A COMPARATIVE STUDY OF VENOUS OCCLUSION AND DDAVP STIMULATED FIBRINOLYSIS IN NORMOLIPIDEMIC SUBJECTS
P. Smith*, H. Arnesen", K.H. Dahl**, D.W.T. Nilsen*, T. Opstad* and P. Andersen" *Red Cross Clinic and **Hemostasis Research Section, Nycomed A/S, Oslo, Norway. (Received 3.5.1988; accepted in revised form 10.8.1988 by Editor H.C. Godal) (Received in final form by Executive Editorial Office 12.10.1988) INTRODUCTION Stimulized release of the vascular plasminogen activator (t-PA) may be brought about by venous occlusion (VO) (1) or may be induced pharmacologically by the vasopressin-analogue DDAVP (1-Desamino-8-D-Arginine Vaso-pressin) (2). The fibrinolytic response to either one of these stimuli may be evaluated in clot lysis systems such as the euglobulin clot lysis time (ECLT)(3), and in assays using chromogenic substrates (4,5). In subjects with hypertriglyceridemia, reduced fibrinolytic response following both VO (6) and DDAVP (7) has been noted. Furthermore, hypertriglyceridemit subjects who are non-responders to venous occlusion in terms of the ECLT, may be responders to DDAVP (8). Previous studies comparing DDAVP and VO in normals are small and do not provide information on lipoprotein levels in the tested subjects (9-11). In the present study we have investigated single fibrinolytic variables and ECLT following stimulation by VO and DDAVP in 21 healthy normotriglyceridemic volunteers. SUBJECTS AND METHODS Subiects The study population comprised 21 healthy volunteers, 12 males and 9 females. Mean age was 40 years (range 21 - 51) and mean Body Mass Index was 22.1 kg/m2 (range 18.4-28.0). None of the subjects had a history of thromboembolic disease, none were taking any drugs and none of the women were taking oral contraceptives. Testing Procedures All tests were performed in the fasting condition between 8 and 10 a.m. Before ----~---~~~-~~~~~-~~~~~~~~~~~ Key words: Venous occlusion, DDAVP, fibrinolysis. 655
656
STIMULATEDFIBRINOLYSIS
Vol. 52, No. 6
stasis, blood was collected for determination of plasminogen activator inhibitor (PAI), triglycerides and baseline t-PA. Venous stasis was applied to the upper arm with a sphygmomanometer cuff of 90 mm Hg for 20 minutes (1). Blood samples for determination of fibrinolytic capacity by the ECLT and t-PA measurements were collected from an antecubital vein of the occluded arm just prior to release of the stasis. After a resting period of 30 minutes, DDAVP (Minirino, Ferring, Maims, Sweden)(0,4pg/kg body weight) was injected over 10 minutes in the arm that had been exposed to venous occlusion. Blood samples were drawn from the contralateral arm 30 minutes later. Analytical Methods Euglobulin fibrinolytic activity was determined in terms of ECLT, mainly as described by Nilsson (3). Results are expressed in minutes (normal 6 45) (12). Acidified plasma was prepared immediately by adding one part 1 M Na-acetate buffer, pH 3.9, to two parts of citrate blood. After centrifugation the plasma was snap-frozen in liquid nitrogen and stored at -7OoC. Specific t-PA activity was determined amidolytically with a chromogenic substrate (PL-l,H-D-Nleu-CHALys-pNA, Nycomed, Oslo, Norway) mainly as described by Wiman (4). The t-PA standard was prepared from melanoma cell cultures as described by Radcliffe et al (13) and calibrated against the international t-PA standard 83/517. Poly-Dlysine (Sigma, St. Louis, U.S.A.) was used as promoter. t-PA antigen (t-PA:Ag) was assayed by an ELISA method using a commercially available kit (Imulyse, Biopool, Umed, Sweden) (5). Values for t-PA activity are expressed as units/ml (U/ml), whereas t-PA:Ag values were estimated as nanogram/ml (ng/ml). One ng t-PA = 0.5 U. The fast acting t-PA inhibitory activity (PAI) was measured amidolytically according to Chmielewska et al (14) and is given as units (U/ml), 1 inhibitor unit being defined as the amount required to neutralize 1 unit t-PA (Spectrolyse, Biopool, Sweden). Mean PA1 level in the reference population of our laboratory was 7*4 (SD). Blood lipids were determined enzymatically by conventional methods (Boehringer Mannheim GmbH, FRG). Statistical Methods Wilcoxon's sign rank test was applied for comparison of data before and after stimulated release of t-PA. The association between variables was measured by the Spearman rank correlation coefficient. A p-value of <0.05 (two-tailed) was considered statistically significant. Group data are reported as medians unless otherwise indicated.
RESULTS Lipids, PA1 and ECLT Triglycerides, total cholesterol and HDL-cholesterol were all within normal limits of our laboratory. PA1 before stimulation revealed values within normal limits (median 1.6 U/L, range O-6). The median value of ECLT following DDAVP was shorter (20 minutes, range 13-40) than that post stasis (30 minutes, range 10-110) (p=O.O25) (fig.1). Four cases exceeded the upper normal limit of 45 minutes (range 55-110) as judged by ECLT after VO, but not so after DDAVP. t-PA and t-PA:Ag Due to hemolysis, determination of t-PA activity was not done in one sample. Median t-PA activity at baseline was 0.2 U/ml (range O-0.9) and t-PA:Ag was 4.3 ng/ml (range l-6.0). There was a statistically highly significant increase
Vol. 52, No. 6
STIMULATED FIBRINOLYSIS
657
of plasma t-PA (antigen and activity) (p
1
U/ml
I.5 6-
30 30
I
4.8
4_
min.
20
2-
Jl 2.2
1.1
0.2
P
t-PA t-PA:Ag BASELINE
0.7 CT:
;
r t-PA
t-PA&A:""
t-PA:Ag vo
-
;
ooAEVCPLT v”
FIG. 1 Median t-PA activity and t-PA antigen (converted to units) before and after DDAVP and VO. Median ECLT (minutes) after DDAVP and VO (right axis). Bars on top of column = 1 SEM.
The four subjects with abnormal ECLT after VO had t-PA activity readings that were distictively lower than after DDAVP (Fig 2). A similar pattern was seen regarding t-PA:Ag measurements.
L t-PA (VO) t-PA (DDAVP)
v
t-PA:Ag (VO) t-PA:Ag (DDAvP) w FIG. 2 Ranked values of t-PA response in terms of t-PA activity and t-PA antigen. Low (L) and high (H) end of array respectively. 0 Denotes normals and ??denotes low responders in terms of ECLT after VO. Correlations The ECLT after VO and DDAVP, respectively, were only weakly correlated (r==0.3, p = 0.11). t-PA activity following the two procedures were well correlated,
658
however between
STIMULATED FIBRINOLYSIS
Vol. 52, No. 6
(r=0.51, p=O.O2). There was no statistical significant correlation t-PA:Ag following the same stimuli (r=0.19, p=O.42).
DISCUSSION A brisker fibrinolytic response in terms of ECLT has been found following DDAVP compared with VO in hypertriglyceridemic subjects (8). Some studies have addressed the same issue in assumed normals (9-11). However, only small numbers of persons have been investigated, and the lipoprotein profile has not been documented. As in hypertriglyceridemics, the subjects in our study were throughout less responsive to VO than to DDAVP in terms of ECLT readings. The weaker responsiveness occurred despite higher levels of t-PA after VO, both when expressed in terms of functional t-PA and as t-PA antigen (fig.1). Our data thus confirm the results of Prowse et al. (9), who compared the hemostatic responses to DDAVP, VO and exercise in 6 male volunteers. In that study euglobulin clot lysis time showed higher fibrinolytic activity after DDAVP-infusion than after VO, whereas t-PA:Ag revealed the opposite pattern. Different results have been obtained by others, however. In a study in 7 normal persons Nilsson et al. found roughly the same responses in terms of fibrinolytic activity following both DDAVP and VO (10). Another paper reporting on effects of DDAVP in patients with panhypopituitarism found both higher t-PA:Ag and euglobulin fibrinolytic activity after DDAVP than following VO in a control group of 6 subjects (11). In the latter study the stimulation tests were performed with an interval of 15 days, and venous occlusion was applied for 10 minutes. The hemoconcentration inevitably occurring during VO may have influenced the concentration of t-PA after this procedure. No correction has been made for such changes. However, the magnitude of changes likely to occur (9), should not have influenced the readings significantly. Fibrinolytic activity following VO is a useful predictor in prethrombotic and thrombotic states (7,15,16). Weak responders to DDAVP have been described in familial thromboembolism (17) and in spontaneous thrombosis (18). Four subjects had abnormal ECLT readings after VO despite normal values following DDAVP. Fig. 2 suggests that at least in some of the cases this may have been brought about by less released t-PA after VO. However, the possibility of different release of PA1 by the two stimulation procedures should be kept in mind. In conclusion, our study has confirmed diversities between response to VO and DDAVP in normolipidemic subjects. Hence, these procedures may not always be compatible. Future studies aiming at elucidating the mechanisms involved should include also determination of PA1 (activity as well as total amount) before and after stimulation. Such studies should additionally take into account the possibility of the two stimuli acting differently on release of t-PA and PA1 from non-endothelial sources. REFERENCES 1. ROBERTSON BR, PANDOLFI M, NILSSON IM. Fibrinolytic capacity in healthy volunteers as estimated from effect of venous occlusion of arms. Acta Chir. Stand. 138,429-36,1972. 2. GADER AMA, da COSTA J, CASH JD.L-desamino-8-d-arginine vasopressin and fibrinolysis in man. Scot. Med. J. 19,56-7,1974
Vol. 52, No. 6
STIMULATED FIBRINOLYSIS
3. NILSSON IM, OLOW B. Fibrinolysis Chir. Stand. 123,247-66,1962.
induced by
streptokinase in
659
man. Acta
4. WIMAN B, MELLBRING G, RANBY M. Plasminogen activator release during venous stasis and exercise as determined by a new specific assay. Clin. Chim, Acta 127,279-88,1983. 5. BERGSDORF N, NILSSON T, WALLEN P. An enzyme linked immunosorbent assay for determination of tissue plasminogen activator applied to patients with thromboembolic disease. Thromb. Haemostas. 50,740-4,1983. 6. ANDERSEN P, ARNESEN H, HJERMANN I. Hyperlipoproteinemia and reduced fibrinolytic activity in healthy coronary highrisk men. Acta Med. Stand. 209, 199-202,1981. 7. BROMMER EJP, BARRET-BERGSHOEFF MM, ALLEN RA, SCHICHT I, BERTINA RM, SCHALEKAMP MADH. The use of desmopressin acetat as a test of the fibrinolytic capacity of patients - analysis of responders and non-responders. Thromb. Haemostas. 48(2),156-61,1982. 8. NILSEN DWT, ANDERSEN P, HJERMANN I, GODAL HC. Discrepancy in fibrinolytic response to desmopressin as compared to venous occlusion. Thromb. Haemostas. 53,60,1985. 9. PROWSE CV, FARRUGIA A, BOULTON FE, TUCKER J, LUDLAM CA, McLAREN M, BELCH JJF, PRENTICE CRM, DAWES J, MacGREGOR IR. A comparative study using immunological and biological assays of the haemostatic responses to DDAVP infusion, venous occlusion and exercise in normal men. Thromb. Haemostas. 51,110-4,1984. lo. NILSSON IM, VILHARDT H, HOLMBERG L, ASTEDT B. Association between factor VIII related antigen and plasminogen activator. Acta Med. Stand. 211,10512,1982. 11. JUHAN-VAGUE 1, CONTE-DELVOX B, AILLAUD MF, MENDEZ C, OLIVER C, COLLEN D. Effects of DDAVP and venous occlusion on the release of tissue-type plasminogen activator and von Willebrand factor in patients with panhypopituitarism. Thrombosis Res. 33,653-9,1984. 12. NORDBY E, ARNESEN H, ANDERSEN P, GODAL HC. The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis. Stand. J. Haematol. 25,407-11,198O. 13. RADCLIFFE R, HEINZE T. Isolation of plasminogen activator from human plasma by chromatography on Lysine-sepharose. Arch. Biochem. Biophys. 189, 185-94,1978. 14. CHMIELEWSKA J, RANBY M, WIMAN B. Evidence for a rapid inhibitor to tissue plasminogen activator in plasma. Thrombosis Res. 31,427-36,1983. 15. ISACSON S, NILSSON IM. Defective fibrinolysis in blood and vein walls in recurrent "idiopathic" venous thrombosis.Acta Chir. Scand.138,313-19,1972. 16. ARNESEN H, SEMB G, HOL R, KARLSEN H. Fibrinolytic capacity after venous stasis in patients undergoing aortocoronary by-pass surgery. Relation to shunt occlusion. Stand. J. u. 30 (supp1),43-6,1983.
660
STIMULATED FIBRINOLYSIS
Vol. 52, No. 6
17. JOHANSSON L, HEDNER U, NILSSON IM. A family with thromboembolic disease associated with deficient fibrinolytic activity in vessel wall. Acta Med. Stand. 203,477-80,1978. 18. ABERG M, NILSSON IM, VILHARDT H. The release of fibrinolytic activator and factor VIII after injection of DDAVP. In: Progress in chemical fibrinolysSamama MM Desnoyers PC is and thrombolysis, Davidson JF, Cepelak V 5. Edinburgh-London-New York: Churchill Livfngstone, 19+9, pp 92-7.