Concentration-dependent dissociation of factor VIII in 1 M NaCl

Plasma, cryoprecipitate, Hemofil, and human factor VIII concentrate were dissolved in 1.0 M NaCl and chromatographed on Bio-Gel A-5m. With high concentrations of factor VIII the activity eluted as a symmetrical peak in the void volume; with a low factor VIII concentration the procoagulant activity was retarded. Dilution curves were performed for several human factor VIII concentrates. When the concentration of factor VIII was decreased, elution patterns showed a gradual transition from a peak in the void volume to a peak with a Ve/Vo of 1.7. Cryoprecipitate exhibited a similar behavior in 1.0 M NaCl, but the percent dissociation was greater than expected at high concentrations of factor VIII. When gel filtration was performed with 0.25 M CaCl2, significant dissociation occurred at all concentrations of factor VIII tested. The behavior of factor VIII in 1.0 M NaCl closely fit a theoretically derived curve for the dissociation of a protein from its binder. We conclude that the dissociation of factor VIII in 1 M NaCl is dependent on the concentration and purification of the procoagulant protein.

Prostaglandin E2 potentiation of platelet aggregation induced by LASS endoperoxide: absent in storage pool disease, normal after aspirin ingestion

Patients with storage pool disease and normal subjects who ingest aspirin show diminished collagen-induced platelet aggregation and an absent second wave of aggregation with ADP or adrenaline. These 'second-phase' aggregation responses are thought to be mediated by cyclic endoperoxide ('labile aggregation stimulating substance', LASS) that is derived from arachidonic acid and is the precursor of prostaglandin E2 (PGE2) and PGE2alpha. Furthermore, although PGE2 does not directly aggregate platelets, it markedly potentiates LASS-induced aggregation. The platelets of six patients with storage pool disease were capable of converting arachidonic acid to LASS, but the potentiation of LASS-induced aggregation by PGE2 was markedly diminished. In contrast, PGE2-potentiation of LASS aggregation was not reduced after aspirin ingestion. The effects of aspirin can be attributed entirely to its ability to block the enzymatic conversion of arachidonic acid to LASS and PGE2. These findings explain why a mutual correction of the aggregation defects is often seen when aspirin-treated platelets are mixed with storage pool-deficient platelets. This is because 'aspirin platelets' aggregate to the mixture of LASS and PGE2 produced by the storage pool-deficient platelets, which are themselves unresponsive. The findings in storage pool disease support previous conclusions that prostaglandin sensitization of platelets to the pro-aggregatory effects of LASS is an important factor in irreversible aggregation, and could be clinically important.

[Adhesion and aggregation in the subendothelium: hereditary platelet function disorder]

Platelet adhesion to a thrombogenic surface and adhesion-induced aggregation were investigated using a perfusion system at a blood flow rate similar to that observed in arteries. Morphometric measurements revealed diminished adhesion of platelets but normal surface-induced aggregation with blood of patients with von Willebrand's disease and with Bernard-Soulier syndrome. In contrast, surface-induced aggregation was defective with blood of patients with storage pool disease, thrombasthenia and with blood of healthy volunteers after Aspirin ingestion. These findings may explain the defective hemostasis in these patients. They suggest that platelet adhesion and aggregation are governed by different mechanisms.

Impaired interaction (adhesion-aggregation) of platelets with the subendothelium in storage-pool disease and after aspirin ingestion. A comparison with von Willebrand's disease

Possible defects in the interaction of platelets with the subendothelial surface were evaluated in six patients with storeage-pool disease, nine patients with von Willebrand's disease and seven normal subjects who ingested aspirin. Citrated blood was perfused through a chamber containing everted segments of rabbit aorta previously denuded of endothelium by means of a ballon catheter. With normal blood, 83.3 +/- 1.9 per cent (S.E.M.) of the surface was covered by adherent platelets. Platelet adhesion was normal after aspirin ingestion (89.7 +/- 4.6 per cent) and decreased in some patients with storage-pool disease. The most striking defect in both circumstances was the virtual absence of platelet thrombi. In contrast, decreased adhesion (57.3 +/- 3.4 per cent), but normal thrombus formation, was characteristic of von Willebrand's disease. These types of defects in platelet adhesion and aggregation may account for the hemostatic defects in a variety of bleeding disorders. The findings further suggest the possible usefulness of aspirin as an antithrombotic agent.

Metal ion contents of gel-filtered platelets from patients with storage pool disease

Platelets from nine patients with storage pool disease (SPD) and from ten control subjects were isolated by gel filtration into a suspension medium permitting the direct determination of platelet Mg-2+, Ca-2+, and K+ levels. The total intracellular levels of ATP and ADP, as well as the incorporation patterns of 14-C-adenine into the metabolic nucleotide pool, were also determined in these platelet suspensions. The gel-filtered platelets (GFP) from SPD patients exhibited slightly lowered levels of ATP and substantially reduced amounts of ADP, in agreement with previous studies using PRP suspensions. Diminished aggregation responses to ADP, epinephrine, and to collagen in particular, similar to those observed previously in PRP, were obtained in GFP from SPD patients. However, GFP from the patients exhibited more variable aggregation responses to addition of ADP and epinephrine than did GFP from the control subjects. Increases in the extent of radioactive hypoxanthine formation, observed previously in normal platelets as a result of isolation into the suspension medium used in these studies, were significantly reduced in the GFP from SPD patients. The levels of platelet Mg-2+ and K+ determined in GFP from the patients were not significantly different from the levels of these ions in GFP from control subjects. However, substantial reductions in platelet Ca-2+ were found in the SPD platelets. A strong correlation was obtained between this reduction in platelet Ca-2+ and the reduction in ADP in these platelets. No such correlation was apparent between the ATP and Ca-2+ deficiencies. These results suggest that a major portion of platelet Ca-2+ may be located in the dense granules and support previous hypotheses that granular ADP and/or Ca-2+ may play a role in the release reaction. The finding of normal levels of platelet Mg-2+ and K+ in SPD platelets, however, suggests that these latter ions are not located in the dense granules.

Content and thrombin-induced release of acid hydrolases in gel-filtered platelets from patients with storage pool disease

The levels of four acid hydrolases, beta-N-acetyl glucosaminidase, beta-glucuronidase, beta-galactosidase, and acid phosphatase, and the extent of their release (release II) by thrombin was determined in platelets from nine normal subjects, nine patients with storage pool disease, and in normal platelets which had been exposed to aspirin. The levels of all four hydrolases were normal in patients with SPD. However, release of three of these hydrolases (acid phosphatase was an exception) by low concentrations of thrombin (0.015 and 0.04 U/ml) was decreased in the patients as a group, although considerable variation in the extent of release of each enzyme was noted. In contrast, aspirin failed to inhibit release II in normal platelets (except for a slight impairment in the release of beta-N-acetyl glucosaminidase), although release I (serotonin, ATP and ADP) was inhibited. All release defects could be overcome by using higher concentrations of thrombin (0.2 U/ml). The normal levels of acid hydrolases in the platelets of patients with SPD (who are deficient in the platelet dense granules) suggest that these enzymes are not normally stored in the dense granules, but rather in alpha-granules. The findings also support the conclusions of previous studies that the release reaction is impaired in SPD. This release defect appears to be different from that seen in normal platelets after exposure to aspirin.

Abnormalities of factor VIII and platelet aggregation--use of ristocetin in diagnosing the von Willebrand syndrome

Ristocetin was used to study platelet aggregation in platelet-rich plasma and to assay the von Willebrand factor activity of factor VIII (VIII-VWF). Ristocetin-induced platelet aggregation (RIPA) was decreased in 13 of 18 patients with von Willebrand's disease (VWD) who had decreased plasma levels of VIII-VWF. The five patients with normal RIPA appeared to have mild VWD but did not constitute a separate subclass. RIPA was also abnormal in some patients with intrinsic platelet defects, but in no case was the defect corrected by normal plasma. The latter type of correction appears to be specific for VWD. Aspirin ingestion inhibited the second phase of RIPA (at low concentrations of ristocetin only) but did not affect the initial phase of aggregation or the level of VIII-VWF. We also studied a group of patients who had both abnormalities of the factor VIII complex and intrinsic platelet defects, such as impaired collagen-induced aggregation, as well. The findings in these patients and in those with typical von Willebrand's disease appear to comprise a spectrum of disorders (the von Willebrand syndrome) in which some abnormality of the factor VIII complex is associated with impaired platelet function. At present, ristocetin would appear to be a useful reagent for evaluating patients with bleeding disorders and for studying patients with the von Willebrand syndrome.

Disseminated intravascular coagulation as a complication of abdominal aortic aneurysm repair

A retrospective review was done of all patients undergoing surgical repair of abdominal aortic aneurysm (AAA) on whom coagulation studies were obtained. Those patients with laboratory documented disseminated intravascular coagulation (DIC) were selected and their clinical records reviewed. This included 7 patients studied in the periods 1964-1965 and January 1971-July 1973. Of these 7 cases, 4 occurred in patients undergoing emergency operation for ruptured aneurysm and 3 were in elective cases. All 7 patients exhibited clinical evidence of abnormal bleeding, while 6 of the 7 progressed rapidly to renal shutdown. The seventh patient recovered spontaneously. Of the 6 patients with full blown clinical and laboratory evidence of DIC, 2 recovered. Both cases received heparin therapy and multiple hemodialyses. A third patient was started on heparin but died at 36 hours in heart failure. All 3 patients receiving heparin showed clinical cessation of abnormal bleeding and disappearance of soluble fibrin monomer complexes within 24 hours of starting therapy. The study suggests a higher incidence of DIC than has previously been appreciated in both the emergency and elective repair of AAA. The prompt recognition and treatment of this complication may reverse the abnormal intravascular clotting, minimize its more serious results and avoid futile and dangerous operative intervention.

Studies of platelet 5-hydroxytryptamine (serotonin) in storage pool disease and albinism

Platelets in patients with storage pool disease are markedly deficient in a nonmetabolic (storage) pool of ADP that is important in platelet aggregation. They are also deficient in ATP, although to a lesser degree. In seven patients with this disorder, including one with albinism, platelet 5-hydroxytryptamine (5-HT) levels were reduced in proportion to the reduction in ATP (r = 0.94). Their platelets show diminished capacity to absorb [(14)C]5-HT, and the type of defect was similar to that produced in normal platelets by reserpine, a drug known to inhibit the uptake of 5-HT by the platelet dense granules. Storage pool-deficient platelets also converted more [(3)H]5-HT to [(3)H]5-hydroxyindoleacetic acid than did normal platelets, and the platelets in one of two patients studied contained increased amounts of 5-HT metabolites. The above findings, together with those reported previously, support the conclusion that the capacity of the dense granules (which may be either diminished or functionally abnormal) for storing 5-HT is decreased in storage pool disease; as a result, the 5-HT that enters the platelet may be more exposed to monoamine oxidases present on mitochondrial membranes. This diminished storage capacity (for 5-HT) may also explain why preincubating platelet-rich plasma with 5-HT for 45 min without stirring inhibits subsequent platelet aggregation by 5-HT to a greater degree in patients with storage pool disease than in normal subjects. The latter finding is also consistent with the theory that the aggregation of platelets by 5-HT is mediated by the same receptors on the plasma membrane that are involved in its uptake. The diminished release of platelet-bound [(14)C]5-HT by collagen that we found in these patients, as well as findings in previous studies, suggests that the release reaction may also be abnormal in storage pool disease.

Acetylenic analog of arachidonate that acts like aspirin on platelets

Development of irreversible platelet aggregation and the accompanying release of platelet-bound serotonin and production of prostaglandins is suppressed by 5,8,11,14-eicosatetraynoic acid (TYA). These findings may be explained by an ability of TYA to inhibit the enzymatic conversion of arachidonate to a newly recognized factor, labile aggregation-stimulating substance, which induces platelet aggregation, and to prostaglandins E(2) and F(2alpha).