The characterization and synthesis of antigens related to factor VIII in vascular endothelium

Extracellular matrix permits the expression of von Willebrand's factor, uptake of di-I-acetylated low density lipoprotein and secretion of prostacyclin in cultures of endothelial cells from rat brain microvessels

Microvascular endothelial cells from the adult rat brain were cultured on Matrigel and found to express many differentiated properties including secretion of prostacyclin (PGI2) and von Willebrand's factor (vWF). Brain microvascular endothelial cells (BMECs) were purified by dextran and percoll gradients after enzymatic treatment and cultured under various conditions. BMECs that were plated on Matrigel stained positively for factor VIII-related antigen and incorporated Di-I-acetylated low density lipoprotein, whereas BMEC plated on fibronectin, gelatin, or uncoated dishes did not express any of the above properties which are characteristic of endothelial cells. vWF was measured by a sensitive ELISA in the culture media of BMECs plated on different types of matrices. Specificity of the anti-human vWF antibodies for the rat vWF was verified by immunoabsorption on a solid phase, sodium dodecyl sulfate, and Western blot analysis. BMECs also secreted vWF into the culture media only when the cells were plated on Matrigel, and this secretion was augmented after a 6 h incubation with an interleukin-1 tumor necrosis factor-alpha mixture, but not by lipopolysaccharide. From different matrices tested, only Matrigel permitted the secretion of PGI2 by BMECs. Cells also proved to be sensitive to mechanical stimulation and became refractory to secretagogue if the mechanical stimulation was serially repeated. Under the best conditions, stimulation of the cells with bradykinin (1 microM) substantially increased PGI2 secretion. These data indicate that growth of BMECs on Matrigel in vitro permits the expression of classical endothelial cell markers in a manner similar to the behavior of these cells in situ.

Morphologic aspects and morphogenesis of blood cysts on canine cardiac valves

We investigated retrospectively the morphologic aspects of blood cysts of the atrioventricular valve in eight Beagle dogs and clarified the morphogenesis of the lesions. Study of serial sections revealed that the cysts communicate with the blood vessels; however, they showed no connection with the valve surface. Immunohistochemically, the thin endothelium of the lesions showed positive staining for factor VIII-related antigen. Histologic studies of a variety of sizes of blood cysts revealed four basic stages of blood cyst formation: 1) initially, the involved blood vessel undergoes only a slight enlargement that is not grossly detectable; 2) next, the vessel becomes moderately or markedly dilated and contains a large number of erythrocytes. The changes of this stage are macroscopically detectable; and 3) then, blood flow is arrested partly in the cystic lesion, followed by degeneration and necrosis of the cyst. At this third stage, fibrous tissue or dense collagenous connective tissue is usually seen surrounding the cyst; 4) and finally, metaplastic bone is formed within the lesion. Colloidal carbon infusion into the valves of normal canine hearts revealed the presence of an extensive, dense arrangement of blood vessels in the septal leaflet of the tricuspid valve, which usually is the recognized site to develop blood cysts.

von Willebrand factor and its disorders: an overview of recent molecular studies

von Willebrand factor (vWF) is a plasma protein with multiple functions in haemostasis. The vWF gene, located on chromosome 12p2.1, encodes a primary gene product of 2813 amino acids. Post-translational modification, assembly and secretion of vWF are highly complex. The pro vWF promoter is covalently linked by intermolecular disulphide bonds to form a dimer of MW approximately 440 kDa. This then polymerises to form multimers ranging in MW from 1-20 x 10(6). Simultaneously the pro piece of vWF is cleaved, releasing a 741 amino acid peptide known as vW Ag II from the polymerised protomers. Two distinct secretion pathways are found in the endothelial cell, a regulated pathway with storage in Weibl-Palade bodies and a constitutive pathway. Platelets store vWF in their alpha-granules. Mature vWF participates in platelet adhesion, spreading and aggregation and is a carrier of factor VIII, protecting the latter from degradation. Disorders of vWF are highly diverse. At least 20 subtypes of von Willebrand's disease have been described to date, based on features of the vWF present in or absent from patients plasma and platelets. Some patients have reduced amounts of apparently normal vWF whilst others have clearly abnormal vWF with aberrant structure and function. Rare patients virtually or completely lack vWF. The genetic and structural basis of some of these abnormalities is just beginning to emerge. This article outlines the molecular biology and physiology of vWF, and reviews some recent progress on the molecular pathology and genetics of von Willebrand's disease.

Giant-cell arteritis. Histological, immunohistochemical and electronmicroscopic studies

Biopsies from the temporal artery of 32 patients suspected of giant-cell arteritis were evaluated retrospectively by light microscopy, histochemical, and immunohistochemical methods, as well as by transmission electron microscopy (TEM). At the clinical follow-up the 32 patients included four clinical groups: temporal arteritis (8 patients), polymyalgia rheumatica (10 patients), rheumatoid arthritis (4 patients), and a group of miscellaneous diseases unrelated to inflammatory rheumatic diseases (10 patients). There were a number of similarities between age-related alterations in the arteries and the changes in giant-cell arteritis. The most important differences were the inflammatory cellular infiltration of the media, the perifocal accumulation of fibronectin, and the occurrence of deposits of fibrin/fibrinogen and fibrin/fibrinogen degradation products. In addition, alpha-2 macroglobulin, lysozyme and factor VIII were also noted in giant-cell arteritis. The alterations in giant-cell arteritis show a number of similarities to the changes following experimental vascular injury of the rabbit aorta. The nature of the findings in human giant-cell arteritis, as well as the similarity to the experimental arteritis, indicate that giant-cell arteritis may reflect a non-specific reaction to injury, independent of the cause of the disease.

Enhanced release of von Willebrand factor by human endothelial cells in culture in the presence of phorbol myristate acetate and interleukin 1

Human umbilical vein endothelial cells (EC) were cultured in the presence of 4 beta-phorbol 12-myristate 13-acetate (PMA), interleukin 1 (IL-1) and interleukin 2 (IL-2), and secretion of von Willebrand factor activity (vWF, Ristocetin Co-factor) and von Willebrand factor antigen (vWFAg) measured at intervals. The levels of both vWF and vWFAg in cultures containing IL-1 were significantly higher than those in control cultures after longer than 5-6 days growth. Similarly, the levels of vWF and vWFAg were significantly increased in cultures containing PMA, but in these instances the rate of cell growth appeared to be enhanced, and confluence was observed after 6 days compared to 9-10 days in control cultures. vWF and vWFAg also increased significantly in the supernatant of confluent control EC incubated further with IL-1. Moreover, the immuno-fluorescence pattern of vWFAg in these treated cells was markedly less granular than that of control cells. Immuno-fluorescence of PMA-treated cells suggested that vWFAg might be less granular than in control EC but the mean levels of vWF and vWFAg in the supernatant of cells incubated with PMA were not significantly different from control values. The results of all assays in the presence of IL-2 were not significantly different from those of control cells. In all instances no morphological evidence of endothelial injury was observed, and more than 90% of cells remained viable at the termination of cultures. The results indicated that the synthesis and release of vWF were increased in the presence of PMA, and secretion of vWF was stimulated by IL-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioinvasion in breast carcinoma. An immunohistochemical study of factor VIII-related antigen

Histologic sections from 63 patients with infiltrating duct carcinoma of the breast were selected for study by immunohistochemical staining with antibody against human Factor VIII-related antigen. Of these 63, 30 had no lymph node metastases at the time of surgery, while 33 had axillary lymph node metastases. A positive correlation exists between the presence of vascular invasion and lymph node metastases. Sixty-nine percent of patients with lymph node metastases had vascular invasion while only 26% of patients without lymph node metastases showed evidence of invasion of blood vessels. The finding of vascular invasion by tumor in patients without axillary lymph node metastases at the time of mastectomy may explain the occurrence of disseminated disease years after treatment.

Neoplastic transformation of the rat visceral yolk sac by polyoma virus

The transforming activity of polyoma virus was verified in vitro in organ cultures of 12-day old rat visceral yolk sacs and embryos. Organ cultures of 18-day old fetal organs were also included. The transforming capacity of the virus was found to be restricted to the endothelial cells of the rat visceral yolk sac. The neoplastic endothelial cells are readily transplantable and possess the polyoma tumor-specific transplantation antigens (TSTA).

Immunocytochemical localization of factor VIII-related antigen in tumors of the human central nervous system

Using both immunohisto- and immunocytochemical techniques with periodate-lysine-paraformaldehyde (PLP) fixation, we have studied the distribution of Factor VIII-related antigen (FVIIIR:Ag) in 12 cases of tumors of the human central nervous system (CNS) and one sample of non-tumor brain tissue. FVIIIR:Ag was found both extracellularly and intracellularly. It was localized in the vascular lumen, between endothelial cells, and in the endothelial cell basement membrane. In the endothelial cell cytoplasm, FVIIIR:Ag was found in the endoplasmic reticulum, perinuclear space, and in intracytoplasmic vacuoles and vesicles. Characteristic of malignant tumors (six out of seven) was a strongly-positive dilated endoplasmic reticulum. This may reflect increased FVIIIR:Ag synthesis in the endothelial cells of malignant tumors. Only one of five benign tumors showed such staining. Six of 12 tumors and the non-tumor brain showed perinuclear FVIIIR:Ag. Both ad- and abluminal vesicles in the tumor endothelial cells contained FVIIIR:Ag suggesting that endocytosis, transcellular transport, and/or endocytosis, as well as FVIIIR:Ag synthesis occurs. The non-tumor brain showed normal capillary structure and very little FVIIIR:Ag immunoreactivity. The relationship of these FVIIIR:Ag abnormalities to the hypercoagulable state seen in some malignant brain tumor patients remains to be clarified.

Factor V in human vascular endothelium and in endothelial cells in culture

Human blood vessels and human umbilical vein endothelial cells in culture were examined for the presence and synthesis of factor V. Factor V antigen was detected on the luminal surface of blood vessels washed with buffers containing calcium but was absent from segments of the same vessels perfused with buffers containing EDTA. Very low levels of endogenous factor V antigen were found in endothelial cells in culture but these cells did not synthesise factor V in sufficient quantities to be detected by the present methods. Factor V activity was not detected in any of the present cell preparations.

The relationship between von Willebrand factor antigen and fibronectin in human plasma, endothelial cells and fibroblasts in culture

The distribution of von Willebrand factor antigen (vWFAg) and fibronectin (Fn) in endothelial cells and in fibroblasts in culture was examined using immunohistological methods. Extracellular matrices were studied after removal of cells by mild hypotonic lysis. Co-distribution of these antigens was also examined after culture of fibroblasts in the presence of endothelial cell conditioned medium or of exogenous vWFAg. The presence of intracellular vWFAg and its association with extracellular Fn in confluent endothelial cells was confirmed. Furthermore, both antigens were detected in matrices from fibroblasts grown in the presence of human plasma and endothelial cell medium. vWFAg was not found, however, in the absence of endothelial cell conditioned medium or in experiments using human serum in place of plasma. Cross-linking of vWFAg was examined using quantitative and qualitative electrophoretic methods. Levels of vWFAg in serum from patients with severe Haemophilia A were approximately 50% of those found in the corresponding plasma. Furthermore, vWFAg was reduced to similar levels in serum from normal blood to which heparin was added. The lowest levels of vWFAg were found in the presence of sufficient heparin to totally inhibit the formation of fibrin. In contrast, levels of Fn remained unchanged in these circumstances. The results did not support the view that vWFAg was cross-linked to Fn in plasma by thrombin-activated factor XIII. In addition, immunoelectrophoresis of cultured endothelial cell products did not demonstrate cross-linking of vWFAg to Fn. The data are consistent with the concept that deposition of vWFAg on the subendothelium is dependent on viable endothelial cells or on another product of these cells.

Increase in factor VIII clotting activity in the perfusate of isolated dog hind leg and heart by components of kallikrein-kinin system

Transient increase in Factor VIII clotting (F.VIIIc) activity was observed by infusion of kallikrein or bradykinin (BK) to the isolated dog leg or heart preparation which was perfused with physiological solution, but the increase in Factor IX activity was not observed, suggesting that the increase in F.VIIIc activity was not due to contaminated plasma components of the perfusate. The increase coincided with the increase in prostacyclin (PGI2) which was determined by immunoassay of 6-keto-PGF1 alpha and by platelet aggregation inhibiting activity. Although increase in PGI2 by BK was inhibited by the pretreatment of the preparations with indomethacin or tranylcypromine, the increase in F.VIIIc activity was not inhibited, suggesting that the increase in F.VIIIc activity was not mediated by PGI2.

Von Willebrand factor levels do not predict or diagnose radiation pneumonitis

In search for an index of endothelial injury that would provide an early diagnosis of radiation pneumonitis, we investigated the plasma levels of von Willebrand Factor (Factor VIII Related Antigen, FVIII:RAg) in 14 patients undergoing pulmonary irradiation. This study was based on observations indicating that damage to the endothelium-rich pulmonary parenchyma may produce alterations in the synthesis, storage or release of FVIII:RAg, detectable in plasma. There was no correlation between FVIII:RAg levels and radiation pneumonitis, radiation dose, volume of irradiated lung, tumor burden, or time-interval between exposure and sampling. The heterogeneity of the neoplasms and the inconstant effects of radiation in the tumor vasculature are among several variables that may explain this lack of correlation. The plasma levels of FVIII:RAg cannot be used to diagnose or predict radiation pneumonitis.

Angiofollicular lymph node hyperplasia (Castleman's disease): an immunohistochemical and enzyme-histochemical study of the hyaline-vascular form of lesion

Tissues from five cases of angiofollicular lymph node hyperplasia have been studied. All had the histological structure of the hyaline-vascular type of lesion; large numbers of very compact lymphoid follicles were distributed evenly throughout a highly vascular tissue. The follicles were characterized by their small size, a vascular poorly cellular and frequently hyalinized centre, and a 'tight' concentric mantle of small lymphocytes arranged in layers producing an 'onion-skin' appearance. The interfollicular tissue was characterized by the large numbers of small vessels mainly hyalinized capillaries and a few high endothelial venules and the presence of variable numbers of lymphocytes, plasma cells, immunocytes and immunoblasts. The immunoperoxidase method demonstrated polytypic cytoplasmic immunoglobulin in the small numbers of centroblasts and plasma cells within the follicle centres and in the plasma cells and immunocytes in the interfollicular tissue. Large numbers of suppressor T cells were present in the interfollicular areas and only scattered helper T cells were seen within the lymphocyte mantles. A strong reaction for factor VIII-related antigen was seen in the endothelium of the interfollicular high endothelial venules but only a weak reaction in the vessels in the follicle centres. A concentric distribution pattern of the dendritic reticulum cells was seen with the metalophil impregnation method of Marshall and with the enzyme histochemical methods for acid alpha-naphthyl acetate esterase and 5'-nucleotidase. This pattern differs from the zonal distribution of these cells seen in reactive lymphoid follicles. The nature and possible pathogenesis of AFLNH are discussed and contrasted with reactive hyperplasia.

The peroxidase antiperoxidase staining of factor VIII-related antigen on cultured endothelial cells

To prevent the premature occlusion of vascular prostheses, endothelium is being cultured experimentally onto synthetic flow surfaces. A rapid method of identifying cultured endothelium on the prosthesis is valuable for determining the degree of fibroblast and smooth muscle cell contamination and to screen for endothelial cell transformation. Fluorescent Factor VIII related antigen (FVIII-RA) staining has been used to identify cultured endothelium, but results in excessive staining of the underlying prosthesis, loss of morphologic detail, and deterioration of the FVIII-RA antibody reaction with time. We have applied the peroxidase antiperoxidase (PAP) method of antigen staining to permit staining of FVIII-RA and thereby to permit a sensitive and specific identification of human or canine endothelium with a concurrent analysis of morphologic detail.

Histochemical studies of intercellular components of salivary gland tumors with special reference to glycosaminoglycan, laminin and vascular elements

In 41 salivary gland tumors, the characteristics of the intercellular components and vascular endothelial cells were surveyed by immunohistochemical staining for laminin and factor VIII-related antigen (VIII R:Ag), and by mucopolysaccharidase-digestion for glycosaminoglycan (GAG). In myxomatous areas of pleomorphic adenomas, small vessels (diameter 6.5 +/- 0.11 micron) were frequent and found to be negative or weakly positive by VIIIR:Ag staining although endothelial cells were clearly positive for VIIIR:Ag in capsule surrounding the tumor tissues. Alcian blue stainability was diminished by treatment with both Streptomyces hyaluronidase and chondroitinase. By laminin staining, a vascular pattern was clearly detected, but the majority of tumor cells were not stained. In adenomatous areas, the basement membrane-like linear laminin-staining reaction was observed to be weak and inconsistent around some tumor cell nests. However, in adenoid cystic carcinomas, laminin-positivity was much more intense than in other tumors such as pleomorphic adenoma, mucoepidermoid tumor and adenocarcinoma. In cylindromatous areas, the inner luminal surface in the pseudocysts was markedly positive for laminin, and there was weak positivity around tumor cell nests having a trabecular pattern. By immunoelectron microscopy, a juxtacellular network of replicated basal lamina of tumor cells which lined the inner surface of pseudocysts was positive for laminin. Alcian blue-positivity in the pseudocyst was abolished with heparitinase and chondroitinase, but not with hyaluronidase.

The effect of calcium on the secretion of factor VIII-related antigen by cultured human endothelial cells

Cultured human endothelial cells derived from the umbilical cord vein are able to release factor VIII-related antigen into the culture medium. The experiments described in this paper show the presence of two pathways for the secretion of factor VIII-related antigen from endothelial cells. There is a basal release of this antigen, independent of the presence of extracellular calcium ions. This release can be inhibited by cycloheximide and is therefore directly related to de novo protein synthesis. Besides this basal release, there is an extra release of factor VIII-related antigen that can be stimulated by thrombin, the Ca2+-ionophore A23187 or phorbol myristate acetate. As demonstrated by immunofluorescence, the stimulus-inducible release originates from storage granules in the cells. This stimulus-inducible release is dependent on extracellular Ca2+ but independent of intracellular cAMP.

Differential localisation and synthesis of porcine factor VIII related antigen (VIIIR:AG) in vascular endothelium and in endothelial cells in culture

Porcine and human umbilical vein and adult blood vessels were studied for the presence and synthesis of factor VIII related antigen (VIIIR:Ag) and fibronectin (Fn) by immunofluorescence histology and immunoautoradiography. Investigation of human tissue confirmed the widespread distribution of VIIIR:Ag on the endothelium of all blood vessels examined but observations on porcine tissue gave different results. Porcine umbilical vein and porcine adult veins were positively stained for VIIIR:Ag whilst porcine aorta and other pig arteries appeared to be negative or only weakly positive. Some blood vessels (?venous) in the adventitia of porcine aorta were positively stained whilst adjacent ones (?arterial) were negative. Radiolabelled methionine was added to culture medium and proteins synthesised by cultured EC were examined by two dimensional crossed immunoelectrophoresis and autoradiography. Identification of radiolabelled precipitin arcs provided a highly sensitive method for confirming the specificity of antisera and for detecting VIIIR:Ag and Fn. Examination of cultured human umbilical vein EC confirmed the synthesis of VIIIR:Ag and distinguished between VIIIR:Ag and Fn. Studies of porcine umbilical vein EC in culture gave similar results to those observed with corresponding human EC. However, cultures derived from porcine aorta did not demonstrate synthesis of VIIIR:Ag and microscopy failed to locate VIIIR:Ag in these cells with certainty. The results confirmed the synthesis of VIIIR:Ag by human and porcine umbilical vein EC but differences in staining reactions and the apparent inability to synthesise VIIIR:Ag by cells derived from porcine aorta suggested that porcine EC at different anatomical sites may subserve different functions.

Proliferative response of human endothelial cultures to various types and treatments of human sera, to culture treatments and to various oxygen concentrations

Endothelial cells from the human umbilical vein were exposed to different human sera, differently treated serum, to various oxygen concentrations, and various culture treatments. Endothelial proliferation was determined by measuring the uptake of [3H]-thymidine by means of autoradiography and presented as thymidine labeling index (TI) values. TI values differed according to different serum concentrations, serum types, serum preparations (WBS-PDS) and serum pretreatments. Low oxygen concentrations in the incubator atmosphere induced an early DNA synthesis response without an increase in cell number. The addition of the protease inhibitors aprotinin and soybean trypsin inhibitor to the culture medium resulted in a dose dependent TI decrease, whereas PMSF showed no influence.

Synthesis and release of factor VIII by cultured human endothelial cells

Endothelial cells (ECs) derived from human umbilical veins were cultured in order to study the physiological control of factor VIII synthesis and release. The culture media were studied from multiple replicate cultures at confluence. Factor VIII related antigen (VIIIR:Ag) and factor VIII coagulant antigen (VIII:CAg) were measured by sensitive immunoradiometric assays. De novo synthesis of factor VIII related protein (VIII:R) was quantitated by incorporation of labelled amino acids into specific protein subunits. The following agents were added to the culture medium in a range of concentrations from physiological to pharmacological: adrenaline, 5 hydroxytryptamine, 2,3-DPG, cyclic AMP, thyroxine, hydrocortisone, and human growth hormone. None of them had any effect at any concentration on the rate of accumulation of VIIIR:Ag in the culture medium. Addition of exogenous factor VIII had no effect on do novo synthesis of VIII:R. VIII:CAg was found to be stable under the conditions of culture but none was released from the ECs. Long-term monocyte cultures also failed to release VIII:CAg. It appears that VIII:R is a constitutive gene product of umbilical vein endothelial cells and that VIII:CAg is not made by these cells.

Factor VII related antigen as an endothelial cell marker in benign and malignant diseases

The presence and distribution of Factor VIII related antigen (FVIIR:Ag) in formation fixed, paraffin embedded tissue were studied in benign and malignant vascular tumors, inflammatory vascular diseases, normal tissue from various organs and a number of malignant tumors. The unlabeled peroxidase-anti-peroxidase method was utilized. Immunostaining was observed only in endothelial cells, in tumor cells of endothelial cell origin and in megakaryocytes and platelets. The staining method gave a distinct picture of the vascular pattern in all types of tissue examined. The demonstration of FVIIIR:Ag by means of the immunoperoxidase technique is considered a valuable method in diagnosing tumors of vascular origin. The method also facilitates detection of vascular invasion of malignant tumors in small caliber vessels.

Angiolymphoid hyperplasia with eosinophilia simulating lymphadenopathy

A case of angiolymphoid hyperplasia (AHE) with eosinophilia presenting with recurrent inguinal swellings simulating lymphadenopathy is described. Tissue was examined by light microscopic techniques, electron microscopy and immunohistochemistry. Electron microscopy showed large numbers of cytoplasmic filaments and bizarre Weibel-Palade bodies in the atypical endothelial cells that characterize AHE. Factor VIII related antigen was demonstrated in a small proportion of these cells by immunoperoxidase staining. The absence of staining for lysozyme and alpha 1 antitrypsin does not support the concept that these cells are histiocytic in nature. The prominent lymphoid and plasma cell proliferative elements in this case showed a polytypic staining pattern for immunoglobulin. An unusual reticular staining pattern for IgE was observed in the lymphoid follicles. The nature and pathogenesis of AHE is discussed in the light of previous publications and the findings in this case.

Multiple molecular forms of endothelial cell factor VIII related antigen

Heterogeneous factor VIII related antigen isolated from endothelial cell postculture medium was characterized. On crossed immunoelectrophoresis, slow moving less anodal populations of factor VIII related antigen molecules were more prominent in endothelial cell postculture medium than in plasma. The protein synthesized by endothelial cells appeared as two discrete protein bands of different molecular weight in sodium dodecyl sulfate polyacrylamide gels. In contrast the factor VIII related antigen isolated from plasma moved as a single protein band in an identical gel system. The factor VIII related antigen from endothelial cell postculture medium was immunoisolated using monospecific rabbit antibody to normal human plasma factor VIII related antigen, electrophoresed on sodium dodecyl sulfate polyacrylamide gels, radiolabeled with 125I, trypsinized and subjected to peptide mapping using two-dimensional high voltage electrophoresis and thin-layer chromatography. The two forms of endothelial cell factor VIII antigen had virtually identical peptide maps. These studies suggest that the molecular heterogeneity of the factor VIII related antigen system reflects polymeric associations of identical subunits. Circulation in vivo may alter the ratio of polymer subsets.

Binding and release of factor VIII/von Willebrand's factor by human endothelial cells

The uptake and release of factor VIII/von Willebrand's protein by cultured human umbilical vein endothelial cells have been examined using highly purified 125I-factor VIII possessing von Willebrand's factor activity. 125I-factor VIII/vWF was taken up by the cells, reaching maximum binding within 4 h with a t1-2 of binding of 15 min. Endothelial cell binding of 125I-factor VIII/vWF reached saturation at a concentration of 1.5 mg/l. Binding was inhibited by coincubation of excess unlabelled factor VIII/vWF. Most of the cell-associated radioactivity was released by treatment of the cells with trypsin. Internalization of bound protein was evidenced by the incorporation into the cells of radioactivity which could not be released by trypsin. Human vascular smooth muscle cells did not bind 125I-factor VIII/vWF. Addition of 0.1 microM epinephrine to the 125I-factor VIII/vWF labelled endothelial cultures induced the release of cell bound, protein-associated radioactivity into the medium. Propranolol inhibited completely epinephrine-induced release, whereas phenylephrine had no effect. Endothelial cells maintained in medium partially depleted of factor VIII/vWF by tricalcium citrate cellulose treatment of plasma did not release factor VIII antigen into the culture medium during subsequent incubation. Although [3H]proline was incorporated into proteins released by endothelial cells under these experimental conditions, specific incorporation of label into factor VIII/vWF antigen was not detectable by a sensitive solid-phase immunoradiometric assay. We conclude that factor VIII/vWF binds to endothelial cells and that this cell-bound protein is mobilized by epinephrine through beta-adrenergic stimulation.

Factor VII and fibrinolytic response to deamino-8-D-argenine vasopressin in normal subjects and dissociate response in some patients with haemophilia and von Willebrand's disease

Deamino-8-D-argenine vasopressin (DDAVP) was given by intravenous infusion to normal subjects, haemophiliacs and patients with von Willebrand's disease (vWd) and the factor VIII and plasminogen activator response was studied. In normal subjects and most patients with mild haemophilia and mild (intermediate) von Willebrand's disease there was an increase in plasminogen activator and all factor VIII related activities. In patients with mild vWd the prolonged bleeding time was shortened by DDAVP despite only a modest rise in factor VIII related Ristocetin cofactor activity (VIIIR:RiCoF). Sub-groups of patients have been characterized in whom atypical responses was observed. In two brothers with clinically severe haemophilia, but with 5--6 u/dl procoagulant factor VIII (VIIIC), there was an increase in VIIIC but no rise of the corresponding antigen, suggesting increased release of an antigenically abnormal poorly functioning molecule. A patient with intermediate vWd was studied in whom neither DDAVP, adrenaline infusion, nor venous occlusion resulted in an increase in either plasminogen activator or factor VIII related antigen (VIIRAg), although there was a significant increase in VIIIC. In a further patient with severe vWd, DDAVP failed to elicit any plasminogen activator or VIII response. The results obtained from these two patients suggested that in some individuals the presumed endothelial cell abnormality in vWd may be more extensive than a defect in VIIIRAg synthesis. Sub-groups of patients have been identified for whom treatment with factor VIII concentrates would be more appropriate than DDAVP prior to minor surgery.

Characterization of procoagulant activity produced by cultures of human monocytes and lymphocytes separated in colloidal silica-polvinylpyrrolidone gradients

Human peripheral blood leucocytes were examined for their ability to synthesize procoagulant activity in tissue culture. A method was developed utilizing silica coated with polyvinylpyrrolidone (Percoll) to separate monocytes from lymphocytes prior to culture. Coagulation activity was demonstrated in all mononuclear cell cultures after 24 hours incubation. This activity was inhibited by phospholipase C which suggested that tissue thromboplastin was the major source of activity. Specific immunoradiometric assays failed to demonstrate synthesis of factor VIII related antigen (FVIIIRAG) or factor VIII coagulant antigen. The results indicate that under conditions of this study factor VIII was not synthesized in mononuclear cell cultures.

Synthesis of procoagulant factor VIII, factor VIII related antigen and other coagulation factors by the isolated perfused rat liver

The synthesis of factor VIII and other coagulation factors has been studied using an isolated, perfused rat liver. Synthetic function of the liver was validated by adding [35S]L-methionine to the perfusion medium and performing two-dimensional crossed immunoelectrophoresis and autoradiography on samples obtained during perfusion. Progressive incorporation of radioactivity into plasma proteins was demonstrated. This was inhibited by cycloheximide. Coagulation factor assays demonstrated synthesis of factors II, IX and X and of factor V and procoagulant factor VIII (VIIIC). Synthesis of factor VIII related antigen (VIIIRAg), measured in an immunoradiometric assay, was not significantly demonstrated. Addition of warfarin to the perfusion medium inhibited the synthesis of factors II, IX and X but not of factors V and VIII. Cycloheximide completely inhibited synthesis of all coagulation factors but actinomycin acted only after a latent period. Reticuloendothelial cell blockade was attempted by adding ethionine to the perfusion medium or by administration of Indian ink to the donor animals prior to removal of the livers. In these instances synthesis of factor V and factor VIIIC was inhibited but not that of factors II, IX and X. The results confirmed the functional capacity of the isolated liver for synthesizing proteins and the vitamin K dependent coagulation factors, and suggested similar kinetic features for the synthesis of factors V and VIIIC. Failure to detect significant VIIIRAg synthesis in these experiments is consistent with the hypothesis that this protein is released by vascular endothelial cells throughout the body and is activated or joined to VIIIC or stimulates its production in the liver.

Abnormal factor VIII in chronic renal failure

Factor VIII procoagulant activity (VIII-C), related antigen (VIII-AG), and von Willebrand factor (VIII-vWf) were measured in 38 patients with chronic renal failure (CRF), in 19 patients with normal renal function from a general medical ward, and in 17 normal subjects. Wide variation in the levels of factor VIII (FVIII) functions were found in the group of CRF patients. There was no correlation between the levels of the three individual activities of FVIII in renal disease. The levels of the three functions were elevated in the patient controls and no significant differences were found between the two groups of patients, although both groups were significantly different from the normal subjects. Increased electrophoretic mobility (EM) was detected in 22 of the 38 patients with CRF (58%) compared to seven of the 19 patients controls (37%). These studies suggest caution in interpretation of changes in FVIII status in patients with other clinical disorders, such as liver disease.