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K T Preissner

Publications and source records attributed to K T Preissner.

At least 73 records · Page 4Linked to original sources
PubMed1996

Modification of vitronectin by advanced glycation alters functional properties in vitro and in the diabetic retina.

Early diabetic retinopathy is characterized by areas of acellular capillaries and the accumulation of advanced glycation end products (AGE). Endothelial cell maintenance, growth, and migration is regulated by a complex system involving the partitioning of growth factors between extracellular matrix-bound proteoglycans and cells, as well as by the activation and control of pericellular proteolysis. Using specific antibodies, we compared the immunolocalization of the vascular heparan sulfate proteoglycan (HSPG)-binding protein vitronectin (VN), HSPG, basic fibroblast growth factor, and collagen type 1 in retinae prepared from 11-month-old diabetic and nondiabetic Wistar rats. In normal rats, VN immunostaining was prominent in vascularized parts of the inner retina and colocalized with HSPG, which itself showed costaining with basic fibroblast growth factor in the extracellular matrix, vascular walls, and the inner limiting membrane. In contrast, the recognition of VN, HSPG, and basic fibroblast growth factor in diabetic retinae was greatly reduced in the inner limiting membrane and the extracellular matrix, where increased immunoreactive AGE colocalizing with VN were detectable. Capillary labeling of retinal vessel walls for plasminogen activator inhibitor-1 was moderate in both normal and diabetic retinae. AGE-VN was demonstrated in tissue extracts from retina by immunoprecipitation and Western blotting and presented a similar increase of AGE-related immunoreactivity compared with AGE-VN generated in vitro. AGE-VN in vitro had lost its native conformation, yielded high Mr SDS-resistant products, and was resistant to proteolysis because of modification of about 30% of lysines. Because binding of glycosaminoglycans, as well as interaction of type I collagen and the morphoregulatory proteins osteonectin and tenascin with AGE-VN, were reduced to at least 50% of control, alteration of basic residues in the heparin-binding domain of VN is plausible. In comparison to nonmodified VN, AGE-VN exhibited reduced cell attachment-promoting activity. Together, these in vitro results suggest that AGE-VN found in vivo is related to morphologic and functional changes in the diabetic retina and may contribute to the genesis of acellular capillaries in early diabetic retinopathy.

Animals↗
PubMed1995

Internalization of vitronectin-thrombin-antithrombin complex by endothelial cells leads to deposition of the complex into the subendothelial matrix.

Internalization of the ternary vitronectin-thrombin-antithrombin (VN-TAT) complex by human umbilical vein endothelial cells was investigated. Radiolabeled VN-TAT was bound to the cell surface at 4 degrees C, and internalization was initiated by increasing the temperature to 37 degrees C. After 30 min about half of the VN-TAT complex disappeared from the cell surface and accumulated in the subendothelial matrix. Translocation of VN-TAT complex from the luminal to the basolateral side was confirmed by electron microscopic evaluation of cross-sections of endothelial cells incubated with gold-conjugated VN-TAT complex. Furthermore, cells cultured in VN-TAT deficient serum, incubated with purified VN-TAT, and subsequently assayed for fluorescent staining using a monoclonal antibody directed against thrombin-modified antithrombin and a polyclonal antibody against vitronectin showed co-localization of both antibodies in punctates. Punctates were randomly distributed in both the xy and xz plane of endothelial cells as evidenced by confocal laser scanning microscopy. Trichloroacetic acid precipitation and SDS-polyacrylamide gel electrophoresis showed that VN-TAT was not degraded during translocation and inhibition of the microfilament system reduced release of VN-TAT to the matrix, indicating that transcytosis was responsible for translocation. These findings emphasize that VN-TAT complex is taken up by endothelial cells, not only leading to the removal of inactivated thrombin from the circulation but also to deposition of VN into the subendothelial matrix.

Antithrombin III↗
PubMed1995

Fibronectin, laminin, vitronectin and their receptors at newly-formed capillaries in proliferative diabetic retinopathy.

Proliferative diabetic retinopathy (PDR) is characterized by intraocular formation of fibroglial vascularized tissue by active vasoproliferative mechanisms. Using immunocytochemistry, we have studied changes in the distribution pattern of fibronectin (FN), laminin (LN), vitronectin (VN) and their receptors in the newly-formed capillaries of PDR. In intraocular vascularized tissue of PDR patients, FN was present on both luminal and basal surfaces of endothelial cells, and was diffusely distributed in the interpericyte space. LN was also associated with the interpericyte space. VN was occasionally detected on the luminal capillary side, but was frequent in the basal aspect of the endothelium in the interpericyte space, where it was colocalized with FN. Beta-1 subunit complex receptors were detected on the luminal side, while alpha v beta 3 integrin was identified on both sides, more so in the luminal than in the basal endothelial domain. By slot-blotting techniques and densitometric analysis, increased concentrations of intravitreous FN and VN were found in PDR in comparison with normal samples. These results suggest that FN, VN and LN have a key role in the structural arrangement of newly formed capillaries in PDR, and that receptor expression could be involved in events of endothelial cell adhesion and proliferation.

Adult↗
PubMed1995

PCR-amplified vitronectin mRNA localizes in situ to spermatocytes and round spermatids in the human testis.

Vitronectin is an adhesion protein present within the acrosomal cap region of human spermatozoa and is liberated during the acrosome reaction. The purpose of this study was to determine if vitronectin mRNA was synthesized in the male genital tract using the reverse transcriptase in-situ polymerase chain reaction (PCR) technique. Twelve genital tract tissues, which included six testes, one showing Sertoli cells only and one from a 3 year old boy, as well as sections from the prostate, seminal vesicles, and epididymis, were analysed for vitronectin transcripts. PCR-amplified vitronectin cDNA was detected in the seminiferous tubules of the four adult testes that showed normal spermatogenesis and localized to the spermatocytes and round spermatids. PCR-amplified vitronectin cDNA was not detected in the tissues of the prostate, epididymis, and seminal vesicles from the men whose testes did contain the message, nor in the testes with Sertoli cells only or that of the prepubertal boy. It is concluded that, in the male genital tract, vitronectin is transcribed exclusively in the germ cells at the spermatocyte and round spermatid stages. This demonstrates that the translated protein present in the spermatozoon is being produced in situ. Further study is needed to determine the role of this protein in the dynamics of sperm-oocyte interaction.

Adult↗
PubMed1995

Vessel wall-dependent metabolic pathways of the adhesive proteins, von-Willebrand-factor and vitronectin.

The integrity of the vessel wall under quiescent conditions as well as its appropriate responsiveness under conditions of stimulation, inflammation or vascular injury is controlled by a number of adhesive interactions involving distinct cellular receptor systems and various multifunctional adhesive ligands. While a number of these extracellular matrix components of the vessel wall are endogenously produced, secreted and deposited, exogenous adhesion proteins may become translocated from the intra- to the extravascular space by virtue of endothelial cell-specific transport systems. Two prominent examples for each metabolic pathway are discussed. Endothelial cell-specific biosynthesis and secretion as well as deposition of multimeric von-Willebrand-factor within intracellular granules (Weibel-Palade bodies) relates to the first possibility of processing, whereas binding of reactive forms of circulating vitronectin to diverse cellular receptors with subsequent extravasation and deposition into the extracellular matrix appears to be characteristic for the second case. In this review the known features of the metabolic routes of both adhesion proteins are discussed and set in perspective to their functional properties. Their localized mode of action in the vessel wall appears to be crucial for balanced haemostasis and immune systems, two major defence mechanisms of the organism.

Animals↗
PubMed1995

Inhibition of thrombin by antithrombin III and heparin cofactor II in vivo.

The critical role of thrombin in the pathogenesis of venous and arterial thrombosis, and the effectiveness of glycosaminoglycans as antithrombotic drugs are well known. Antithrombin III is a major inhibitor of thrombin and augmentation of its inhibitory actions by heparin is the basis for the clinical uses of heparin. Recent clinical and experimental studies have demonstrated that another glycosaminoglycan, dermatan sulfate, is an effective antithrombotic drug. Dermatan sulfate catalyses the inhibition of thrombin by heparin cofactor II. The concentrations of heparin cofactor II are higher in the plasmas of individuals with congenital antithrombin III deficiency and pregnant women than controls. The role of heparin cofactor II as a physiologic thrombin inhibitor is unknown. Enzyme-linked immunosorbent assays were used to quantify thrombin-heparin cofactor II and thrombin-antithrombin III endogenous to the plasmas of adult antithrombin III-Hamilton deficient subjects, their siblings with normal antithrombin III levels, pregnant women at term and 3 to 5 days after delivery. Both thrombin-antithrombin III and thrombin-heparin cofactor II complexed with vitronectin were detected in all the plasmas. Significantly, the concentrations of thrombin-heparin cofactor II-vitronectin were higher in the plasmas of congenital antithrombin III deficient subjects and in pre- and post-delivery plasmas than those of normal subjects. In addition, the concentrations of thrombin-heparin cofactor II decreased 3 to 5 days after delivery, reflecting the disappearance of the catalytically active dermatan sulfate elaborated by the placenta. Thus, heparin cofactor II normally inactivates thrombin in vivo, with its role increasing in conditions associated with high levels of heparin cofactor II and/or dermatan sulfate.

Adult↗
PubMed1995

Acquired protein C dysfunction but not decreased activity of thrombomodulin is a possible marker of thrombophilia in patients with lupus anticoagulant.

Lupus anticoagulants (LAs) are acquired antiphospholipid antibodies, and the occurrence of LA is associated with an increased risk of developing thrombosis. In a population of 46 patients with LA with or without LA-associated thrombophilia, it was analyzed whether the concentration of LA could be correlated to the individual thrombotic risk in patients with LA. No significant difference was found in the concentrations of LA measured by routinely used functional and immunologic assays in patients with LA with thrombophilia when compared with patients with LA without thrombophilia. Inhibition of thrombomodulin (TM) activity by LA has been postulated to be one of the major pathogenic mechanisms causing thrombophilia in LA. Therefore the inhibition of endothelial cell-dependent TM activity by LA was analyzed by using a protein C (PC) activation assay. Reduced rates of PC activation were found in only 2 out of the 46 cases, ruling out that inhibition of TM activity is a common phenomenon in patients with LA. However, anionic phospholipids are necessary to ascertain the anticoagulant activity of activated PC (APC). To prove the hypothesis that the anticoagulant activity of APC is inhibited by LA, the anticoagulant response of purified APC added to LA-containing plasma was measured through the amount of factor VIII inactivation. Thirteen out of 14 patients with recurrent thrombotic events and 10 out of 19 patients with one single episode of thrombosis showed an APC response outside the mean--2 SD range of normal human controls. In contrast, among 13 patients with LA without symptoms, only one showed an abnormal APC response. From these data it is concluded that LA inhibits the APC anticoagulant activity and that this type of acquired APC dysfunction may contribute to the pathogenesis of LA-associated thrombophilia. Moreover, the APC anticoagulant response assay may prove to be a useful marker to identify patients with LA with a high thrombotic risk.

Adult↗
PubMed1994

Determination of the vitronectin binding site on plasminogen activator inhibitor 1 (PAI-1).

Vitronectin is the carrier protein of plasminogen activator inhibitor 1 (PAI-1). We used a well-characterized panel of anti-human PAI-1 monoclonal antibodies (MoAbs) to localize the vitronectin-binding site on PAI-1. By employing a direct vitronectin/PAI-1 binding assay and two vitronectin-dependent inhibition assays, we demonstrate that the anti-PAI-1 MoAbs CLB-5, CLB-10, CLB-2C8 and I1, directed against different epitopes in the region between amino acids 110 and 145, prevent the interaction of PAI-1 with vitronectin. We conclude that the region between amino acids 110 and 145 of PAI-1 harbours an important determinant for the interaction with vitronectin.

Amino Acid Sequence↗
PubMed1994

Clustering of vitronectin and RGD peptides on microspheres leads to engagement of integrins on the luminal aspect of endothelial cell membrane.

In previous work (Conforti et al, Blood 80:437, 1992), we have shown that integrins in endothelial cells (EC) are not polarized to the basal cell membrane, but are also exposed on the apical cell surface, in contact with blood. Therefore, endothelial integrins might be available for binding circulating plasma proteins. However soluble plasma vitronectin (vn) bound very poorly to EC apical surface and this interaction was unaffected by Arg-Gly-Asp (RGD) peptides or an anti-alpha v beta 3 serum. In contrast, beads (diameter, 4.5 microns) coupled with plasma vn associated to EC apical surface in a time- and concentration-dependent way. Addition of antibodies directed to vn, alpha v beta 3, and RGD-containing peptides blocked the interaction of vn beads with EC. In contrast, heparin and antibodies directed to alpha v beta 5 and beta 1 integrin chain had no effect. Beads coupled with Gly-Arg-Gly-Asp-Ser-Pro bound to the EC surface, but not those coupled with Gly-Arg-Gly-Glu-Ser-Pro. This interaction was blocked by alpha v beta 3 antibodies and RGD peptides, but not by alpha v beta 5 antibody. Overall, these results indicate that luminal alpha v beta 3 retains its binding capacity for surface-linked vn and RGD-containing ligands, but binding is observed only when the ligand is offered in a clustered, multivalent form. We propose that when vn or RGD-containing proteins are bound to circulating cells, they can act as bridging molecules by promoting adhesion of the cells to the endothelium via apical integrins.

Amino Acid Sequence↗
PubMed1994

Pericellular enzymatic hydrolysis: implications for the regulation of cell proliferation in the vessel wall and the bone marrow.

The stromal microenvironment in the vessel wall as well as in the bone marrow provides specific adhesion molecules for cell-cell and cell-matrix interactions and allows a variety of growth factors to be positioned at the cell surface or the extracellular matrix for optimal signal transmission. While cell proliferation and differentiation within the different haematopoietic lineages in the bone marrow is a continuous process leading to the generation and egression of mature blood cells, endothelial and smooth muscle cells in the intact undisturbed vessel wall retain a non-proliferative quiescent cell phenotype. This changes drastically upon vascular injury, which is followed by the activation of the haemostatic system combined with a variety of growth modulatory reactions necessary for the wound healing. Several locally expressed enzymatic systems including the plasminogen activator/plasmin system, endoglycosidases and phospholipases are operative in a concerted fashion to modify the pericellular microenvironment in order to allow cell migration and invasion, but also to participate in the balance of growth regulatory processes. In particular, localization and presentation as well as mobilization and activation of growth factors are coordinated by a number of hydrolytic processes. The major components of the hydrolytic enzyme systems involved in pericellular modification as well as the consequences for the regulation of cell proliferation in the hydrolytic enzyme systems involved in pericellular modification as well as the consequences for the regulation of cell proliferation in the vessel wall and the bone marrow are discussed.

Bone Marrow↗
PubMed1994

Calcium-dependent activation of protein C by thrombin/thrombomudulin: role of negatively charged amino acids within the activation peptide of protein C.

In the absence of its cofactor thrombomodulin (TM) thrombin is only a poor activator of the anticoagulant serine protease protein C (PC). The TM-dependence of PC-activation has been restricted to a series of molecular structures of the PC molecule including high-affinity calcium binding sites and single amino acid residues. However, thrombin induced activation of a PC derivative altered in all these critical positions is markedly enhanced by TM indicating that additional structures of the PC molecule are involved in determining the TM specificity. Based on the hypothesis that such an additional regulatory element should be located near the thrombin cleavage site and should include negatively charged amino acids to ascertain calcium binding, we studied whether Glu and Asp in positions P7 and P6 relative to the thrombin cleavage site together with Asp in P3 are involved in formation of such a regulatory element. Three PC derivatives containing the neutral counterpart of the negatively charged amino acids in positions P3; P3 and P6; and P3, P6, and P7, respectively, were generated using site-directed mutagenesis. Compared to rPC-wt the initial rates of PC activation of all three mutants were increased 4.0-fold for thrombin/TM and 4.0-, 5.3-fold for activation by thrombin alone. However, compared to the PC derivative neutralized exclusively in P3, additional changes in P6 and P7 showed no increase in the thrombin activation kinetics and calcium binding properties were identical in all of the three mutants.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Multiple interactions between human vitronectin and Staphylococcus aureus.

Multiple interactions between human vitronectin and Staphylococcus aureus strain V8 were observed. An upward-curved Scatchard plot indicated both high-affinity binding (Kd1 = 7.4 x 10(-10) M) with 260 binding sites per bacterial cell and moderate-affinity binding (Kd2 = 7.4 x 10(-8) M) with 5240 copies per cell. Negative cooperativity of this binding was characterized by its Hill coefficient of less than unity (0.70 +/- 0.08). Up to 60% of the vitronectin-bacteria interaction was unaffected by high ionic strength (i.e., 2.4 M NaCl), and was not inhibited by highly-charged heparin oligosaccharides. Various oligosaccharides (4-20 monosaccharide units) generated by partial deaminative cleavage of heparin were found to affect vitronectin binding to S. aureus. Short-chain-length oligosaccharides increase and long oligosaccharides inhibit vitronectin binding, in accordance with direct association of these saccharides with multimeric vitronectin. A protein having a molecular mass of 60 kDa was identified as a putative high-affinity staphylococcal vitronectin-binding protein. These results indicate that interaction of multimeric vitronectin, mostly present at extracellular matrix sites with multiple recognition sites on the S. aureus surface, may contribute to bacterial colonisation.

Binding Sites↗
PubMed1993

Multimeric vitronectin. Identification and characterization of conformation-dependent self-association of the adhesive protein.

The adhesive glycoprotein vitronectin (VN) shows a high degree of conformational flexibility implicating that different molecular forms of the molecular may exist. Conformation-dependent monoclonal antibodies 13H1 or 16A7 that, per se, did not react with plasma VN bound to VN treated with heparin, chaotropes, detergents, pH below 6, or by heating at 56 degrees C. Dependent on the stimulus, recognition of VN by these antibodies varied and preceded heparin binding and self-association of VN resulting in the formation of noncovalently linked multimeric species of the protein. Both monoclonal antibodies also reacted with VN in serum or in platelet releasates as well as with VN in extracellular matrices of endothelial cells and inhibited cell adhesion on immobilized VN. Critical VN levels were needed for concentration-dependent multimerization indicating a nonlinear type of polymerization process. The nature of VN multimers was judged by nondenaturing gel electrophoresis, gel filtration, and sucrose gradient ultracentrifugation and revealed the formation of 3- to 16-mer multimeric species within an M(r) range of 200-1200 kDa representing a mean sedimentation coefficient of 9.6 S. In electron microscopy, multimeric VN occurred as globular specimens with an average diameter of 15-28 nm (monomeric plasma VN, 6-8 nm). In contrast to plasma VN, VN multimers were efficiently stabilized by covalent inter-molecular bonds following chemical or transglutaminase-induced cross-linking. A synthetic peptide comprising the central heparin binding region of VN (residues 348-361) not only bound to plasma VN but induced its multimerization also in plasma. During plasmin proteolysis of VN, fragments were generated that lacked the heparin binding region and that lost the ability to multimerize following urea or detergent treatment, implicating that the highly basic region is essential for multimer formation. These data suggest that non-plasma forms of VN, which are abundant in platelets and subendothelium, represent the prototype conformer of the reactive heparin binding form of VN. Our findings implicate that conformationally altered forms of VN enable the adhesive protein to multimerize in a characteristic fashion and thereby endow extracellular matrix sites with unique multivalent properties.

Amino Acid Sequence↗
PubMed1993

Heterogeneous lipoprotein (a) size isoforms differ by their interaction with the low density lipoprotein receptor and the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor.

Lipoprotein (a) (Lp(a)) is a complex of low density lipoprotein (LDL) with apolipoprotein (apo) (a). To examine the size distribution of Lp(a), plasma was separated by fast flow gel filtration and Lp(a):B complexes were determined in the eluate by enzyme immunoassays, in which detection was performed with monoclonal antibodies specific for apoB. Lp(a):B particles displayed apparent molecular masses (M(r)) of 2 x 10(6) to at least 10 x 10(6). Lp(a) size isoforms differed by the expression of apoB epitopes and their interaction with cultured human skin fibroblasts. LDL was more effective in inhibiting binding, uptake, and degradation of low M(r) Lp(a) than of high M(r) Lp(a). In contrast, Glu-plasminogen, alpha 2-macroglobulin and tissue-type plasminogen activator were more effective in competing for the cellular degradation of high M(r) Lp(a) than of low M(r) Lp(a). Ligand blotting revealed that Lp(a) bound to the low density lipoprotein receptor, the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP) and to two other endosomal membrane proteins. We propose that the LDL receptor preferentially internalizes low M(r) Lp(a), whereas LRP may have a role in the clearance of high M(r) Lp(a).

Cells, Cultured↗
PubMed1993

Human megakaryocytes express clusterin and package it without apolipoprotein A-1 into alpha-granules.

Clusterin, a 70-Kd disulfide-linked two-chain plasma glycoprotein circulates in blood as a high-density lipoprotein particle and is highly induced after tissue injury and tissue remodeling. In this study, peripheral blood leukocytes were assayed for clusterin expression. The protein was predominantly detectable in human platelets by immune cytochemistry. The content of clusterin was determined and amounts to 2.5 +/- 1.3 micrograms/10(9) platelets, thus representing about 2% of the blood pool. Clusterin purified from human platelets had the same molecular weight as plasma clusterin under nonreducing conditions and was composed of two disulfide-linked nonidentical subunits of the same size. Both preparations were sensitive to reduction yielding the two subunits of 35 Kd. In contrast to plasma clusterin, the platelet form was not complexed to apolipoprotein A-I. By immunogold labeling, alpha-granule localization of clusterin was observed. Complete release of platelet clusterin occurred at optimal doses of A23187, phorbol myristate acetate (PMA), and thrombin. Because clusterin mRNA was detected by hybridization in situ in bone marrow-derived megakaryocytes, platelet clusterin is most likely produced and packaged into alpha-granules during megakaryocyte development.

Apolipoprotein A-I↗
PubMed1993

Self-association of antithrombin III relates to multimer formation of thrombin-antithrombin III complexes.

During the reaction of antithrombin III (AT III) with target proteases the inhibitor serves as pseudo-substrate and undergoes profound conformational changes, becomes incorporated into a covalent stoichiometric enzyme-inhibitor complex which is, in contrast to native AT III, recognized by monoclonal antibody 4C9. In the absence of the target enzyme thrombin, incubation of AT III with 1-2 M guanidine, 0.6% deoxycholate, heating to 56 degrees C, or buffer at pH 4 resulted in inactivation of the inhibitor with concomitant exposure of the epitope for 4C9 and formation of AT III multimers (from 3.9 S to 7.1-7.4 S). Loss of activity, formation of multimers and exposure of neoepitope(s) of AT III occurred in a concerted fashion and followed second order kinetics with an activation energy of Ea = 31 kcal/mol. AT III-multimerization induced by treatment with 1 M guanidine (mainly AT III-tetramers with M(r) of 250,000) and formation of the binary AT III-thrombin complex revealed similar self-association patterns as judged by gel electrophoresis under non-denaturing conditions. In the presence of heparin, even higher multimers of AT III-thrombin complexes were noted. Moreover, self-association products of the ternary vitronectin-thrombin-AT III complex, which is the ultimate reaction product following thrombin inhibition in the circulation, could be recognized and quantitated due to exposure of the 4C9 epitope on AT III, indicating that AT III exists in multimeric forms within binary and ternary complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1993

Two independent binding sites on monolayers of human endothelial cells are responsible for interaction with coagulation factor VII and factor VIIa.

The interaction of radiolabeled factor VII (FVII) and factor VIIa (FVIIa) with endotoxin-stimulated endothelial cells (EC), known to express tissue factor (TF), and unstimulated EC was studied. FVII/FVIIa binding to EC-monolayers was saturable within 4.5-6 h, reversible, temperature and calcium dependent on both, endotoxin-stimulated and on unstimulated EC. Upon 2 h of incubation on EC, FVII was partially converted to FVIIa in the absence of protease inhibitors. The affinity of this binding was Kd = 45.4 +/- 18.7 nM with a calculated number of binding sites Bmax = 3.75 +/- 0.31 x 10(6) molecules/cell. In addition to unlabeled FVII and FVIIa, other vitamin K-dependent proteins reduced binding of [125I]-FVII/FVIIa to about 60-70%, and this type of common binding site for vitamin K-dependent proteins revealed a Kd = 32.2 +/- 5.6 nM and a Bmax = 3.03 +/- 0.14 x 10(6) molecules/cell. Moreover, in the presence of 1 microM prothrombin to suppress common binding sites, only on endotoxin-stimulated EC additional inhibition of FVII/FVIIa binding was achieved by anti-TF antibodies. The characteristics of the FVII/FVIIa-TF interaction with a Kd = 17.2 +/- 5.2 nM and a Bmax = 342,000 +/- 1,100 binding sites/cell revealed a similar saturation kinetics in radioligand binding and in functional factor X activation within 90-120 min. These data indicate the presence of at least two independent binding sites for FVII/FVIIa on stimulated EC of which about 10% are TF specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗