We have previously reported that amidinonaphthol derivatives, which have been developed as synthetic serine protease inhibitors, inhibited the binding of adhesive proteins, such as fibrinogen and fibronectin, to ADP-stimulated platelets in a competitive manner. Because this effect was similar to those of Arg-Gly-Asp (RGD) peptides, we examined the effect of amidinonaphthol derivatives on the chemical cross-linking of RGD-peptides to stimulated platelets. The radiolabeled peptides including RGD-sequence (RGDSPASSKP and KYGRGDS) were coupled to platelets by subsequent addition of chemical cross-linking agent. Platelet membrane glycoprotein IIb-IIIa (GPIIb-IIIa) became radiolabeled with the RGD peptide, and stimulation with ADP increased the extent of cross-linking. Cross-linking of the labeled peptides to ADP-stimulated platelets was inhibited by excess of nonlabeled RGD peptides, an amino acid sequence of corresponding to the carboxyl terminus of γ-chain of fibrinogen, fibrinogen and fibronectin, but not by Gly-Arg-Gly-Glu-Ser-Pro (GRGESP). The cross-linking reaction was inhibited by addition of amidinonaphthol derivatives, such as nafamostat mesilate or FUT-6258, but less effectively by gabexate mesilate, which does not have amidinonaphthol in the structure. The inhibitory effect of nafamostat mesilate was dose-dependent, and 50% inhibition was obtained at the concentration of 6×10-5M. This result suggested that amidinonaphthol derivatives inhibited the binding of adhesive proteins to platelets by the blockade for RGD peptide binding sites on GPIIb-IIIa.
Anticoagulant profile of low molecular weight heparinoids (KB-101) and its in vivo effects on the experimental DIC (disseminated intravascular coagulation) were investigated in comparison with unfractionated heparin (UFH). KB-101 displayed considerably less effects than UFH on the conventional laboratory tests as activated partial thromboplastin, prothrombin and thrombin time. Both of these agents catalyzed the inactivation of factor Xa by antithrombin III (AT III) and the inactivation of thrombin by AT III and heparin cofactor II (HC II). The potencies of KB-101 on the inactivation of these activated coagulation factors were far lesser than those of UFH. On the other hand, the anti-Xa to anti-thrombin activity ratio of KB-101 was about 28 times higher than that of UFH. Either KB-101 and UFH enhanced the antiplasmin activity in plasma, which was less prominent in KB-101 than UFH. The in vivo effects of these heparin on the endotoxin-induced experimental DIC using rats, were assessed by coagulation and fibrinolytic parameters and the degree of fibrin deposition in the renal glomeruli. The inhibitory effects of KB-101 on DIC were proved to be as equivalent to those of UFH. From these results it was concluded that KB-101 showed a higher anti-Xa to anti-thrombin activity ratio than UFH and revealed a potent inhibitory effects on experimental DIC, which suggested its therapeutic efficacy for DIC.
The activation of prothrombin by prothrombinase complex results in cleavage of the prothrombin molecule into two polypeptides, alpha-thrombin and prothrombin fragment F 1+2. Recently, an enzyme immunoassay (Enzygnost F 1+2; Behringwerke AG, Germany) was developed to measure the activation peptide for the clinical diagnosis of hypercoagulable states. The accuracy and clinical usefulness of this test were evaluated using blood samples of healthy individuals and patients with disseminated intravascular coagulation syndrome (DIC). Plasma F 1+2 levels in the healthy individuals were 0.49±0.29nmol/l (Mean±SD, n=67). The levels in the initial samples of patients with DIC were 10.52±12.99nmol/l (Mean±SD, n=17), which were significantly higher than those in healthy individuals. In cases with improved DIC, plasma F 1+2 levels tended to decrease after starting anticoagulant therapy. However, in the cases showing deterioration high levels persisted. These results suggest that the plasma F 1+2 level well reflects hypercoagulable states in DIC and is a useful molecular marker to monitor the effects of therapy.
Deficiency of protein C has been considered as an increased risk factor of thrombotic disease so far. Deficiency of this protein predisposes to venous thrombosis, but have been very rarely associated with arterial thrombosis. In this study we described a case of multiple cerebral infarction and cerebral arterial thrombosis in a 46-year-old man with heterozygous protein C deficiency (type 1 deficiency). Cranial computed tomography showed multiple hypodensity areas in bilateral basal ganglia, and cerebral angiography demonstrated occlusion in the territory of left posterior cerebral artery. Routine coagulation tests containing Fbg, AT III, Plg, PS and Lp (a) were within normal limits. Hepatic function was also found to be normal. No other risk factors (smoking, dyslipidemia and diabetes) but hypertension for arterial thrombotic disease were present in the propositus. Three other members of this family (mother and two sons) showed the same defect, but they had been asymptomatic. It is considered that congenital protein C deficiency may also be a risk factor for cerebral arterial thrombosis. Protein C activity should be evaluated in patients with juvenile onset of cerebral infarction especially in ones without any known risk factors.
We report a case of pregnancy and delivery of a thromboasthenic woman, who had history of frequent blood transfusions and had anti-platelet antibody (anti-Plt Ab) in her serum. A patient was a 25 year-old primigravida. She was diagnosed as thromboasthenia at 7 years of age, and because of recurrent massive bleeding was transfused many times from her four brothers. She became pregnant and consulted our department. Before delivery, we evaluated her anti-Plt Ab by LCT (lymphocyte toxicity test), AHG-LCT (anti-human globulin lymphocyte toxicity test), and MPHA (mixed passive hemagglutination using platelet), but we could not detect it. Her two brothers were prepared as Plt donors in whose serum no anti-Plt Ab was detected by LCT and MPHA. When the induction of delivery was begun, 27U Plt obtained from the donors was transfused to her. Nevertheless, her Plt count and bleeding time (BT) didn't improve at all. After the donor's 10U Plt and random donors' 70U Plt were transfused, her Plt count, BT and Plt aggregation by ADP were improved, and she delivered a 3620g mature female uneventfully. Bleeding amount was 950ml. Genital bleeding was increased at 3 weeks after delivery, and she fell into severe anemia. 220U Plt and 5U CRC were transfused, but Plt count and BT were not improved at all. Prostaglandin F2α was injected into uterine cervix and ovserved. Thereafter genital bleeding was decreased gradually. After delivery, her serums obtained before and after delivery was examined by sensitive MACE (modified antigen captured ELISA). It revealed that anti-Plt Ab was present in both serum. Thromboasthenic patient who has history of blood transfusion has the possibility of the presense of anti-Plt Ab in his serum. We shold be careful for false-negative results of the examinations of Anti-Plt Ab. Moreover we should take care of bleeding not only at delivery but also at puerperum.