Vascular Plasminogen Activator Research Articles

JCAD promotes arterial thrombosis through PI3K/Akt modulation: a translational study.

Variants of the junctional cadherin 5 associated (JCAD) locus associate with acute coronary syndromes. JCAD promotes experimental atherosclerosis through the large tumor suppressor kinase 2 (LATS2)/Hippo pathway. This study investigates the role of JCAD in arterial thrombosis. JCAD knockout (Jcad-/-) mice underwent photochemically induced endothelial injury to trigger arterial thrombosis. Primary human aortic endothelial cells (HAECs) treated with JCAD small interfering RNA (siJCAD), LATS2 small interfering RNA (siLATS2) or control siRNA (siSCR) were employed for in vitro assays. Plasma JCAD was measured in patients with chronic coronary syndrome or ST-elevation myocardial infarction (STEMI). Jcad-/- mice displayed reduced thrombogenicity as reflected by delayed time to carotid occlusion. Mechanisms include reduced activation of the coagulation cascade [reduced tissue factor (TF) expression and activity] and increased fibrinolysis [higher thrombus embolization episodes and D-dimer levels, reduced vascular plasminogen activator inhibitor (PAI)-1 expression]. In vitro, JCAD silencing inhibited TF and PAI-1 expression in HAECs. JCAD-silenced HAECs (siJCAD) displayed increased levels of LATS2 kinase. Yet, double JCAD and LATS2 silencing did not restore the control phenotype. si-JCAD HAECs showed increased levels of phosphoinositide 3-kinases (PI3K)/ proteinkinase B (Akt) activation, known to downregulate procoagulant expression. The PI3K/Akt pathway inhibitor-wortmannin-prevented the effect of JCAD silencing on TF and PAI-1, indicating a causative role. Also, co-immunoprecipitation unveiled a direct interaction between JCAD and Akt. Confirming in vitro findings, PI3K/Akt and P-yes-associated protein levels were higher in Jcad-/- animals. Lastly, as compared with chronic coronary syndrome, STEMI patients showed higher plasma JCAD, which notably correlated positively with both TF and PAI-1 levels. JCAD promotes arterial thrombosis by modulating coagulation and fibrinolysis. Herein, reported translational data suggest JCAD as a potential therapeutic target for atherothrombosis.

C5a Receptor Targeting in Neointima Formation After Arterial Injury in Atherosclerosis-Prone Mice

Receptor binding of complement C5a leads to proinflammatory activation of many cell types, but the role of receptor-mediated action during arterial remodeling after injury has not been studied. In the present study, we examined the contribution of the C5a receptor (C5aR) to neointima formation in apolipoprotein E-deficient mice employing a C5aR antagonist (C5aRA) and a C5aR-blocking monoclonal antibody. Mice fed an atherogenic diet were subjected to wire-induced endothelial denudation of the carotid artery and treated with C5aRA and anti-C5aR-blocking monoclonal antibody or vehicle control. Compared with controls, neointima formation was significantly reduced in mice receiving C5aRA or anti-C5aR-blocking monoclonal antibody for 1 week but not for 3 weeks, attributable to an increased content of vascular smooth muscle cells, whereas a marked decrease in monocyte and neutrophil content was associated with reduced vascular cell adhesion molecule-1. As assessed by immunohistochemistry, reverse transcription polymerase chain reaction, and flow cytometry, C5aR was expressed in lesional and cultured vascular smooth muscle cells, upregulated by injury or tumor necrosis factor-alpha, and reduced by C5aRA. Plasma levels and neointimal plasminogen activator inhibitor-1 peaked 1 week after injury and were downregulated in C5aRA-treated mice. In vitro, C5a induced plasminogen activator inhibitor-1 expression in endothelial cells and vascular smooth muscle cells in a C5aRA-dependent manner, possibly accounting for higher vascular smooth muscle cell immigration. One-week treatment with C5aRA or anti-C5aR-blocking monoclonal antibody limited neointimal hyperplasia and inflammatory cell content and was associated with reduced vascular cell adhesion molecule-1 expression. However, treatment for 3 weeks failed to reduce but rather stabilized plaques, likely by reducing vascular plasminogen activator inhibitor-1 and increasing vascular smooth muscle cell migration.

Inhibitory effect of anti-hepatitis drug bicyclol on invasion of human hepatocellular carcinoma MHCC97-H cells with high metastasis potential and its relative mechanisms

To assess the anti-invasion effect of bicyclol (1) and its mechanism in human hepatocellular carcinoma (HCC) MHCC97-H cells with high metastatic potential. MTT assay was performed to evaluate the cytotoxicity of 1 to MHCC97-H cells and its inhibitory effect on the adhesion of these cells to laminin (LN) and fibronectin (FN). The anti-invasion effect of 1 was detected in an experiment using a transwell chamber. Transcription of vascular endothelial growth factor (VEGF), nm23-H1, and urokinase-type plasminogen activator receptor (uPAR) mRNAs was determined by an RT-PCR assay. The secretion and expression of α-fetoprotein (AFP) were analyzed by ELISA and flow cytometry, respectively. At concentrations of 10, 50, and 100 μmol/l, 1 obviously inhibited the adhesion of the MHCC97-H cells to LN and FN. The rates of inhibition of MHCC97-H cell invasion by 50 and 100 μmol/l for 1 were 37.3 and 50.2%, respectively. Drug 1 also decreased the expressions of VEGF, nm23-H1, and uPAR mRNA and the secretion of AFP in MHCC97-H cells. At low cytotoxic concentrations, the anti-hepatitis drug 1 demonstrated a significant anti-invasive effect in human HCC MHCC97-H cells with high metastatic potential. The inhibition of the expressions of VEGF, nm23-H1, and uPAR should contribute, at least in part, to the anti-invasion property of 1.

Tumor VEGF expression and serum VEGF levels are independent prognostic factors in curatively resected gastric cancer patients

4021 Background: Increased serum and/or tumor vascular endothelial growth factor (VEGF) and urokinase-type plasminogen activator (uPA) have been shown to predict poor survival in several neoplasms, but their prognostic value in gastric cancer (GC) remains unknown. Methods: Serum VEGF (S-VEGF) and uPA concentrations were measured by commercially available ELISA in 20 healthy controls and 97 GC patients (70% I-II stages) before an R0 gastric resection. Tumor expression of VEGF and uPA were assessed by immunohistochemistry. Additional variables, including demographic, histological and therapeutic data were also evaluated. Univariate (Kaplan-Meier, log-rank test) and multivariate (Cox regression) analyses were performed to select prognostic factors regarding survival and tumor recurrence. Results: S-VEGF, but not uPA levels were significantly higher in GC patients than in controls. After a mean follow-up of 47 ± 3 months, the probability of cancer-related survival at 2, 5, and 10 years was 86%, 69% and 59%, respectively. Univariate analysis identified tumor VEGF expression (p=0.001) and high (> 289 pg/ml) S-VEGF levels (p=0.045), along with pTMN stage, grade of curability, perineural invasion, lymph node ratio, and extent of lymphadenectomy as variables associated with cancer-related survival. The mean disease-free survival was 20 ± 3 months, the probability of tumor recurrence being 78%, 62% and 62% at 2, 5 and 10 years, respectively. Prognostic variables for recurrence were the same as those identified for survival. Multivariate analysis identified tumor VEGF expression and high S-VEGF levels as independent prognostic survival factors. Conclusions: After a long follow-up, tumor VEGF expression and S-VEGF levels are independent prognostic factors for recurrence and survival in curatively resected gastric cancer patients. Such markers for increased angiogenic activity might help to identify patients at high risk of recurrence that could mostly benefit from adjuvant therapies. It is tempting to speculate that trials assessing the potential benefit of a.ntiangiogenic agents might be particularly warranted in patients with resected GC and a highly angiogenic phenotype. No significant financial relationships to disclose.

Hemostasis and Glycemic Control in the Cardiac Surgical Patient

The Centers for Disease Control and Prevention estimate that 6% of the US population meets diagnostic criteria for diabetes mellitus, with at least one third of this group being undiagnosed. A majority of adult blindness, renal insufficiency, and limb amputation may be directly attributed to diabetes. Although the incidence of type 1, autoimmune-mediated diabetes remains relatively stable, increasing age, physical inactivity, and obesity have produced explosive growth in insulin resistance and type 2 diabetes. A direct association between diabetes and atherothrombotic disease remains indisputable. However, recent data further suggest that even minor elevations of fasting plasma glucose, in "nondiabetic" subjects, increase cardiovascular risk. Alterations in hemostasis may play an important contributory role. Both hyperglycemia and hyperinsulinemia induce prothrombotic characteristics, including overexpression of vascular endothelial plasminogen activator inhibitor-1 (PAI-1), down-regulation of fibrinolysis, elevation of plasma coagulation proteins (ie, fibrinogen, factor VII, factor X), and enhanced platelet activation. Furthermore, endothelial dysfunction-characterized by an inflammatory phenotype-commonly accompanies diabetes. Given data supporting prothrombotic potential of both acute and chronic hyperglycemia, aggressive perioperative glucose control appears imperative.

Anti-angiogenic effects of interleukin-12 delivered by a novel hyperthermia induced gene construct

Purpose: Interleukin-12 (IL-12) is a pro-inflammatory cytokine possessing anti-cancer and anti-angiogenic properties. This study quantitatively assessed the anti-angiogenic effect of IL-12 delivered using an adenoviral vector with murine IL-12 placed under control of a heat shock promoter. This approach limits systemic toxicity by restricting IL-12 delivery locally to the tumour. The kinetics of the downstream cytokines interferon-γ (IFN-γ) and interferon inducible protein-10 (IP-10) and other molecules affecting angiogenesis, vascular endothelial growth factor (VEGF) and plasminogen activator inhibitor-1 (PAI-1) were also studied.Materials and methods: 4T1 tumours were grown in Balb/C mice and the AdhspmIL-12 construct was injected intra-tumourally. The tumours were heated after 24 h using a water bath. At various time points post-heating the tumours were collected and quantitatively assessed for cytokine production and vascularity.Results: A significant reduction was seen in the tumour vasculature of the treated group vs. the control group mice. Systemic effects of IL-12 were limited to generalized immunostimulation. No hepatoxicity was noted.Conclusions: This study suggests that IL-12 can be effectively delivered using a gene-based approach with a heat shock promoter. This results in quantitatively measurable anti-angiogenesis and general immunostimulation. The complex inter-play of other pro- and anti-angiogenic factors (IFN-γ, IP-10, VEGF and PAI-1) was also studied.

Vascular plasminogen activator and deep vein thrombosis.

In attempts to determine the aetiology of deep vein thrombosis (DVT) it has been established that some patients with a history of lower limb DVT have a low level of vascular plasminogen activator (VPA) in their superficial hand veins and this combined with a poor VPA release is thought to predispose to thrombosis (1). Hand veins rarely develop thrombosis and so the level of VPA has been measured quantitatively in the more commonly at risk veins of the lower limb. In 6 limbs operated on for varicose veins, paired samples of vein from the groin and from the calf were examined. The median activity score for the groin veins (8138 cpm/micrograms) was significantly higher than the activity in the calf veins (2353 cm/micrograms)(P = 0.01). In 9 limbs amputated for critical ischaemia, paired samples of calf long saphenous vein and soleal vein were examined. The VPA in the former was 1675 cpm/micrograms compared with 6796 cpm/micrograms in the soleal veins. This difference is significant at the 1 per cent level. A correlation has been shown between the VPA content of these two sets of veins (R = 0.87). The low level of VPA in the superficial calf veins may be an aetiological factor in superficial thrombophlebitis, but the commonest site for DVT, the soleal veins of the calf, have a high level of VPA.

Transforming growth factor-beta (TGF-beta) induces vascular endothelial growth factor (VEGF) and plasminogen activator inhibitor-1 (PAI-1) gene expression through Smad3 transcription factor

Transforming growth factor-beta (TGF-beta) induces vascular endothelial growth factor (VEGF) and plasminogen activator inhibitor-1 (PAI-1) gene expression through Smad3 transcription factor

C-type natriuretic peptide (CNP) suppresses plasminogen activator inhibitor-1 (PAI-1) in vivo

Elevated vascular plasminogen activator inhibitor-1 (PAI-1) levels are associated with atherosclerosis. In vitro, C-type natriuretic peptide (CNP) has anti-proliferative effects and inhibits the production of PAI-1 in cultured vascular cells. Whether CNP can affect PAI-1 in vivo, particularly in the setting of atherosclerosis, has not been reported. Using the rabbit carotid arterial collar model of intimal hyperplasia (collar in place for 7 days), PAI-1 protein was compared in normal, vehicle (saline)-collared, and CNP-treated-collared arteries from the same animal. PAI-1 levels were measured by immunohistochemistry and densitometry and by Western blot. CNP was either infused into the peri-arterial space within one collar (10 fmol/h) or infused directly into the arterial lumen under one collar (100 pmol/h). In some rabbits (n=8), superoxide production in collared and normal artery segments was measured in vitro by chemiluminescence. PAI-1 was present throughout the vascular wall. Endothelial PAI-1 was elevated in saline-collared arteries (approximately 16%, P<0.05; n=7 rabbits) compared with normal carotid segments. The collar induced both a neointima that contained PAI-1 and the accumulation of macrophages in the adventitia. Peri-arterial CNP reduced PAI-1 (P<0.05) in the endothelium (33%), adventitia (47%) and neointima (39%), compared with levels in the contralateral, saline-collared carotid artery, while macrophage infiltration was reduced. Elevated superoxide production in collared arteries was not altered by chronic in vivo treatment with CNP (n=8). Peri-arterial CNP treatment did not reduce intimal thickening. Intra-luminal CNP (n=6) reduced endothelial, neointimal and total vessel (Western blot) PAI-1, macrophage accumulation, and intimal thickening (all P<0.05). CNP treatment of collared carotid arteries in vivo for 1 week suppressed endothelial and neointimal PAI-1, independently of intimal thickening. The CNP effects were not via superoxide. This is the first evidence that CNP inhibits activated PAI-1, in vivo.

Regulation of the hypoxia-inducible transcription factor HIF-1 by reactive oxygen species in smooth muscle cells.

Hypoxia is able to activate the expression of a number of genes that are important for the cell to adapt to low oxygen conditions such as erythropoietin, vascular endothelial growth factor (VEGF) or plasminogen activator inhibitor-1 (PAI-1). The major transcription factor involved in the gene induction by hypoxia is the hypoxia-inducible factor-1 (HIF-1) (Semenza et al. 2001) which consists of two subunits, HIF-1 a and HIF-s also known as ARNT. While the ARNT protein is readily found in the cell, the HIF-1 a protein is undetectable under normoxic conditions. In fact, under normal oxygen conditions, this protein is modified by prolyl and asparaginyl hydroxylation, ubiquitinylated and degradated by the proteasome. During hypoxia, hydroxylase activity is reduced, thus allowing HIF-1 a protein levels to increase (Kaelin, 2002). The HIF-1 a protein can then translocate to the nucleus, interact with the ARNT subunit, bind to specific DNA binding sites named hypoxia response elements (HRE) and finally induce transcription of the target genes.

Hemoadsorption in critical care.

This paper concerns the results of endotoxin hemoadsorption therapy using a PMX column in patients with perforative peritonitis complicated by multiple organ failure. The subjects were 31 patients aged 68 +/- 12 years. When systolic arterial pressure decreased to less than 90 mm Hg, endotoxin hemoadsorption was initiated and continued for 2 h. At the completion of endotoxin hemoadsorption, systolic arterial pressure, diastolic arterial pressure, and mean arterial pressure were significantly increased. Platelet count decreased to less than 50,000/mm(3) in 30% of patients. As for cytokines and vascular endothelial cell function markers, interleukin-6 and plasminogen activator inhibitor-1 significantly decreased. These results suggest favorable effects of endotoxin hemoadsorption on the hemodynamic and pathophysiological conditions in patients with septic shock although attention should be given to the decrease in platelet count.

In Vivo Stimulation of Vascular Plasminogen Activator Inhibitor-1 Production by very Low-Density Lipoprotein Involves Transcription Factor Binding to a VLDL-Responsive Element

High plasma levels of plasminogen activator inhibitor-1 (PAI-1) are associated with an increased risk of cardiovascular disease. There is also a close relation between high plasma levels of PAI-1 and hypertriglyceridemia. Cell culture studies have shown that very low density lipoprotein (VLDL) increases the production and secretion of PAI-1 in endothelial cells and hepatocytes, suggesting a possible mechanism for this association. To determine whether VLDL stimulates PAI-1 production in vascular cells also in vivo, Sprague-Dawley rats were injected intravenously with 6 mg/kg of VLDL (derived from human subjects with type IV hyperlipidemia). Previous studies have demonstrated that this results in an accumulation of human VLDL in the aorta and other arteries followed by increased nuclear factor-kappa B (NF-kappaB) activation. Endothelial, but not smooth muscle cells, showed a basal PAI-1 mRNA and protein expression as assessed by in situ hybridization and immunohistochemistry, respectively. Six to twenty-four hours after the VLDL injection, lipoprotein particle accumulation was seen in the aortic wall, which was accompanied by increasing PAI-1 mRNA and protein expression in endothelial and smooth muscle cells. Within the rat PAI-1 promoter we identified a sequence located at -589 to -571 with 74% homology with the recently described VLDL responsive element in the human PAI-1 promoter and located adjacent to a 4-guanosine motif presumably corresponding to the human 4G/5G polymorphism. Transient transfection studies showed that VLDL exerts its stimulatory effects on rat PAI-1 gene expression in vascular cells by interaction with promoter sequences located within bp -656 and -505. Electrophoretic mobility shift assays showed that VLDL increases the binding of as yet incompletely characterized factors to this response element. Taken together these observations support a direct influence of VLDL on vascular PAI-1 gene expression ill vivo. This stimulation is exerted on the level of PAI-1 gene transcription, and involves transcription factor binding to a VLDL responsive element adjacent to a 4G motif within the PAI-1 promoter.

Plasminogen/plasmin system function in mice deficient in stromelysin-1 (MMP-3) or in tissue inhibitor of metalloproteinases type-1 (TIMP-1)

Specific interactions between the plasminogen/plasmin (fibrinolytic) and matrix metalloproteinase (MMP) systems suggest that both systems may cooperate in extracellular matrix degradation. Therefore, the plasminogen/plasmin system function was evaluated in mice with stromelysin-1 (MMP-3) or tissue inhibitor of MMP type-1 (TIMP-1) gene inactivation. Urinary urokinase-type plasminogen activator (u-PA) antigen (120–190 ng/ml) and activity (13–18 IU/ml) levels were similar in both wild-type and gene-deficient mice. Vascular plasminogen activator activity, measured in aorta extracts, was similar for both tissue-type plasminogen activator (t-PA)-mediated activity (8–14 arbitrary units (AU) per mg protein) and for u-PA-mediated activity (25–34 AU per mg protein). The spontaneous thrombolytic potential (lysis of a 125 I-fibrin labelled pulmonary embolus) was comparable in wild-type (MMP-3 +/+ ) and MMP-3 −/− mice (36 ± 6% versus 49 ± 5% after 8 h; P = 0.13), and in wild-type (TIMP-1 +/+ ) and TIMP-1 −/− mice (48 ± 4% versus 48 ± 2% after 8 h). Organ sections did not reveal significant fibrin deposition in the liver of any of the genotypes. Furthermore, in vivo thioglycollate-stimulated macrophages of all 4 genotypes expressed comparable u-PA-mediated plasminogen activating potential and 125 I-fibrin matrix degrading potential. Thus, these data suggest that MMP-3 and TIMP-1 do not play a major role in the generation of fibrinolytic activity mediated via the plasminogen/plasmin system.

Enhanced Vascular Plasminogen Activator (t-PA) Release by Epinephrine in Aged Rats

Adrenergic stimulation induces an acute fibrinolytic response in the vascular wall and can play an important role in limiting thrombus growth. The incidence of thrombotic disease increases with age. As many adrenergic functions are affected by aging, the vascular response to adrenergic stimulation was studied in young (3 +/- 1 months) and aged (18 +/- 3 months) rats, using an experimental model of vascular perfusion. Five min epinephrine (EPI) infusion (0.15-25 microM) induced a dose-dependent increase in tissue-type plasminogen activator (t-PA) release and in perfusion pressure, in both young and aged rats. In the latter, however, the basal activity of t-PA was significantly higher than in young animals (0.22 +/- 0.02 vs 0.13 +/- 0.01 U/ml; means +/- SE; p < 0.01, n = 40) and EPI infusion induced a significantly higher increase in t-PA activity (0.78 +/- 0.06 vs 0.47 +/- 0.08 U/ml, p < 0.01, for 6.25 microM EPI). The response was characterized by a delayed onset. In contrast, the increase in the perfusion pressure by EPI was significantly lower in aged that in young rats, its basal levels being normal. To evaluate whether the increased vascular response of t-PA was peculiar for adrenergic stimulation, we infused platelet activating factor (PAF), an inducer of t-PA release, not related to catecholamines. PAF, during five-minute infusion induced a rapid and dose-dependent (100-1250 pM) increase in t-PA release, to the same extent in both young and aged rats. In conclusion, basal t-PA secretion was increased in aged rats probably as a response of vascular endothelium to chronic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

The vascular plasminogen activator as source of the fibrinolytic potential observed during cardiopulmonary bypass

Increased fibrinolytic activity is a well recognized constant finding observed during cardiopulmonary bypass (CPB). The purpose of the present work was to study and estimate the factors involved in the plasminogen activation and prekallikrein-kallikrein systems in a population of adult patients undergoing open heart surgery with CPB. Plasminogen activator activity determinations with a fibrinolytic method as well as plasminogen activation and prekallikrein-kallikrein determinations with synthetic substrates were carried out. Our results indicate that no active fibrinolysis but a fibrinolytic potential, similar to that observed in blood obtained after venous occlusion, can be demonstrated in circulating plasma during CPB. This fibrinolytic potential is related to the presence of vascular plasminogen activator released from endothelial cells by the CPB stimulus.

Fibrinolytic behaviour during experimental haemorrhagic shock

The plasma levels of functional plasminogen activators and functional plasminogen activator inhibitors were evaluated in the initial period (90 min) of experimental haemorrhagic shock in the anaesthetised dog. Soon after bleeding (5 min) a hyperfibrinolytic state was found: euglobulin lysis time decreased and remained so for 1h, while there was an initial, although transient, increase in plasminogen activators. At 90 min after bleeding, a hypofibrinolytic balance was found, associated with a significant increase of plasminogen activator inhibitors relative to pre-bleeding values. This hypofibrinolysis coincides with a severe depletion of vascular plasminogen activator pool, as evaluated by an histochemical method, on femoral vein segments obtained at 90 min post-bleeding. We conclude that experimental haemorrhagic shock defines a situation of fast transition from hyperfibrinolysis to an intense hypofibrinolytic stage that may be important to explain the pathological heterogeneity found in haemorrhagic events.

A simple quantitative assay of vascular plasminogen activator--not only stimulated fibrinolytic activity but also basal fibrinolytic activity are correlated with venous fibrinolytic activity.

A simple method for the quantitative assay of vascular plasminogen activator is described. From 24 chronic renal failure patients who were undergoing surgery for A/V fistular or shunt construction, samll pieces of artery (mean 7.8 mg, range 3.0 – 18.5 mg) and vein (mean 4.5 mg, range 3.0 – 8.8 mg) were used. The fibrinolytic acitivity was assayed on a well-controlled fibrin plate by only distilled water immersion and incubation at 37°C. Basal fibrinolytic activity was correlated with venous fibrinolytic activity (r = 0.773, p<0.0001) and with arterial fibrinolytic activity (r = 0.55, 0.005<p<0.01). The increment of fibrinolytic activity by venous occlusion was correlated to venous fibrinolytic activity (r = 0.849, p < 0. 0001) but not to arterial fibrinolytic activity (r = 0.34, 0.1<p<0.25).

Comparison of recombinant tissue-type plasminogen activator (rt-PA) expressed in mouse C127 cells and human vascular plasminogen activator (HV-PA)

Tissue-type plasminogen activator produced by recombinant DNA technology (rt-PA) has now been recognized as a promising clot-selective thrombolytic agent. We have compared the properties of rt-PA expressed in mouse C127 cells with those of naturally occurring human vascular plasminogen activator (HV-PA). The molecular weight of HV-PA and rt-PA was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to be approx. 66 000. HV-PA and rt-PA were labile and rapidly lost their activities at pH values below 5.5. The optimum pH of HV-PA and rt-PA for plasminogen activation was around 8.5. HV-PA and rt-PA appeared to be very similar in amidolytic properties, amino-acid composition and carbohydrate composition. Moreover, the N-terminal amino-acid sequence of HV-PA was in good agreement with that of rt-PA. The purified preparations of HV-PA and rt-PA had specific activities of about 250 000 and 600 000 IU/mg, respectively. Both activators bound to fibrin clots to similar degree. In immunodiffusion as well as in the quenching experiments of the fibrinolytic activities, rt-PA appeared to be immunologically indistinguishable from HV-PA. All these findings indicate that rt-PA expressed in mouse C127 cells is identical with naturally occurring HV-PA in physical and chemical properties.

Defective release of vascular plasminogen activator in patients with gynecologic malignancies : Doman KA; Gore M; Miller KE; et al. Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA Gynecol. Oncol.; 23/2 (141–148) 1986

Defective release of vascular plasminogen activator in patients with gynecologic malignancies : Doman KA; Gore M; Miller KE; et al. Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA Gynecol. Oncol.; 23/2 (141–148) 1986

Release Pattern of the Vascular Plasminogen Activator and Its Inbibitor in Human Postvenous Occlusion Plasma as Assessed by a Spectrophotometric Solid-Phase Fibrin-tPA Activity Assay

Vascular or tissue-type plasminogen activator (plasma t-PA) is the circulating physiological fibrinolytic enzyme of endothelial cell origin which function is regulated by fibrin and a specific inhibitor (PAI). To study the pattern of release of t-PA and the behavior of t-PA-PAI complexes in plasma we determined t-PA activity in 44 healthy subjects before and after 10 min of forearm venous occlusion using a new spectrophotometric solid-phase fibrin-tPA activity assay. The assay is based on 1) the high affinity binding of t-PA to fibrin, and 2) the detection of fibrin-bound t-PA by measuring the release of pNA from a chromogenic substrate in the presence of plasminogen. Values at rest were rather undetectable in plasma (0.05 +/- 0.03 IU/ml, in 23 out of 44 samples) but were positively detected in all the euglobulins: 0.88 +/- 0.68 IU/ml. After venous occlusion the majority of plasmas (36 out of 44) showed a slight increase in t-PA activity (0.65 +/- 0.63 IU/ml) as compared to the important level observed in all the euglobulins (9.78 +/- 9.58 IU/ml). So, the ratio plasma/euglobulin t-PA activity was very low (0.06) and remained identical in both pre- and postocclusion samples. However, when diluted plasmas were tested the inhibitory effect disappeared and t-PA activity increased indicating that although t-PA circulates in a neutralized state it can be available for fibrinolysis.(ABSTRACT TRUNCATED AT 250 WORDS)