B. A. Kudryashov

The antithrombotic and thrombolytic activity of tuftsin

It has been established that one of the immune regulatory peptides, tuftsin, with the amino acid sequence Thr-Lys-Pro-Arg, has a depolymerizing effect on fibrin [21 and prevents its polymerization [5]. It has also been shown that tuftsin displays anticoagulant properties [4], which are related to the sequence Pro-Arg [10]. Normal blood contains around 300 gg/liter of tuftsin [8]. Such a concentration in in vitro experiments produces a fibrinolytic effect [4]. Tuftsin may interact in vitro with high-molecular heparin, resulting in the formation of a complex [6] possessing anticoagulant and fibrinolytic properties. Interaction with heparin in vivo may result in a rise of the anticoagulant and fibrinolytic potential of the blood [4]. The capacity of tuftsin to produce antithrombotic and thrombolytic activity in the organism was examined in the present study.

Fibrinolytic and anticoagulant complexes of low-molecular-weight heparin with tuftsin

: The complex of immunopeptide taftsin with low-molecular heparin has been obtained. The complex has fibrinolytic and anticoagulant activities in vitro and in vivo after the injection to albino rats.

Fibrinolytic complexes of low molecular weight heparin with acetylsalicylic acid

It was shown previously that acetylsalicylic acid (ASA) forms complex compounds with high-molecular-weight heparin with a ratio by weight between the reacting components of 10:1 [2, 4]. The resulting complex possessed not only anticoagulant, but also nonenzymic fibrinolytic activity, both in vitro and on intravenous injection into animals [3]. However, besides high-molecular-weight heparin (HMH), its separate fragments may also be present in man and animals [6]. Researchers have recently paid great attention to low-molecular-weight heparin (LMH), which possesses considerable activity as a neutralizer of factor X a but has a weaker action on thrombin than HMH. LMH has been shown to be a powerful antithrombotic agent, and when taken into the body it does not give rise to a bleeding tendency in the case of an overdose [7]. LMH can interact with the vascular endothelium and thereby exert a prolonged and moderate anticoagulant effect in vivo [5]. Considering previous data on the properties of a complex of HMH with ASA [3, 4], as well as information on the high antithrombotic action of LMH, the need has arisen for a study of the ability of LMH to form a complex with ASA. The aim of the present investigation was to obtain an L M H A S A complex, to study its anticoagulant and fibrinolytic properties in vitro, and also to examine the thrombolytic effect of the complex on a model of thrombosis in animals.

Depolymerization of fibrin and nonenzymic fibrinolysis in rabbits on an atherogenic diet with added antioxidants

Fibrin formation can be activatd in hypercholesterolemia [13]. Reduction of the fibrinolytic and anticoagulant properties of the blood [i], increased platelet aggregation [2], and limitation of complex formation by!heparin and blood proteins and amines [3] have been found in animals on an atherogenic diet. Initiation and progression of atherosclerosis are brought about not only by changes in plasma-platelet reactions, but also by deposition of fibrin on the vascular wall. Morphologic studies have demonstrated massive accumulations of fibrin at sites of maximal lipid deposition (cited in [8]).

Plasma anticoagulant and nonenzymic fibrinolytic activity after intravenous injection of heparin-antithrombin III complex into animals

When a protective response of the anticlotting system to the appearance of the enzyme thrombin in the circulating blood is excited, the heparin which is released into the blood flow forms a complex with the thrombogenic blood proteins and biogenic amines [i, 7]. Complexes of heparin with thrombin, fibrinogen, fibrin-stabilizing factor, plasminogen, adrenaline, and many other biologically active compounds possess anticoagulant properties and dissolve unstabilized fibrin [3, 8]. It is also known that antithrombin III (AT III), an inhibitor of several of the blood proteinases, neutralizes activity of the enzyme thrombin by forming a complex with it [I0]. The reaction of complex formation between thrombin and AT III is considerably accelerated by heparin. The mechanism of action of heparin under these circumstances is varied and may evidently proceed in serveral ways: Heparin may react with AT III, may form a complex with thrombin and, finally, may interact with a preformed complex of thrombin with AT III [7, i0]. Preliminary interaction of the inhibitor with heparin before formation of thrombin--~T III complex includes conformational structural changes in the latter~ ~ which activate complex formation and thus bring about more rapid neutralization of the enzyme [6]. Complex formation of heparin with antithrombin III (H--AT III) has been effected~n experiments in vitro. These components take pa~t in the reaction of complex formation in different proportions by weight. The resulting complexes, with components H and AT III in proportions of I:i to 1:7 by weight, possessed well marked anticoagulant activity and caused lysis of unstabilized fibrin in vitro.The binding of 3H-corticosterone by rat alveolar macrophages was studied before and after stimulation with zymosan in vivo. Thirty min after incubation of the macrophagal monolayer from intact animals with 3H-corticosterone accumulation of the hormone by the cells came to an end. As the concentration of 3H-corticosterone in the incubation medium was raised, the binding of the hormone with the saturated (receptor) system of alveolar macrophages terminated upon absorption of 10.6 fmol per 10(6) cells. Further raising of the level of the bound hormone was effected by the unsaturated (lipid) system. Stimulation with zymosan led not only to an increase in the number of the cells of the bronchoalveolar tract but also to an elevation of the intensity of 3H-corticosterone engulfment by alveolar macrophages. The number of binding sites per cell in the zymosan-activated macrophages increased 1.5-fold. This may be an important moment determining the development and liquidation of mononuclear infiltrations in the lung.

Antiplasmin and its action on the process of fibrinolysis under experimental conditions

In the very first studies of the fibrino!ytic system, i t was noted that the plasma and serum may neutral ize the character is t ic proteolyt ic effect of the ac t ive enzyme plasmin (ci ted in [6]). However, the nature of these inhibitors of the fibrinolytic process, as well as their effect upon the process of fibrinolysis, is insufficiently clear. In the opinion of Ratnov et al. (cited in [6]), several inhibitors of fibrinolysin, which possess different physicochemical properties and exert different effects upon the process of fibrinolysis, are found in human blood.

Lipoprotein lipase as humoral agent of the physiological anticlotting system

SummaryExperiments were staged on 450 male albino rats. As established, a stable food lipemia was attained after keeping the animals on a fat diet (according to Wilgram [42,43]) for 8 months. The activity of lipoprotein plasma lipase in such animals was half as compared to control animals which were given the usual laboratory ration. Intravenous injection of heparin led to considerable activation of lipoprotein lipase in experimental animals. However, it did not reach the level attained in control animals after injection of the same doses of heparin. Intravenous injection of thrombin to normal animals led to activation of lipoprotein lipase due to the appearance in the blood of some excess of reflex-secreten heparin by the physiological anticoagulating system [4, 7, 10] in response to the appearance of thrombin in the circulation.Thus, the development of prethrombotic state in animals kept on a fat diet was accompanied by reduction of lipoprotein lipase activity due to deficiency of heparin and partially of the enzyme itself. A conclusion was drawn that lipoprotein lipase was connected with the function of the physiological anticoagulating system.

Investigation of the ability of dicoumarin to prevent thrombosis caused by intravenous injection of massive doses of thromboplastin

SummaryDicoumarin was used to reduce the blood prothrombin to the therapeutic level (25–12%) and below 10% in male albino rats; thrombin formation was induced by thromboplastin administration against the background of the normally functioning anticoagulation system and of its depression (caused by keeping the animals on atherogenic diet and by chloropromazine or potassium chloride administration). As established, reliable protection from thrombosis could be attained only by reducing the prothrombin level below the 10% mark. The most prothrombin state developed after intravenous injection of potassium chloride.

Prophylaxis of experimental thrombosis in splenectomized animals by intravenous injection of fibrinolysin and heparin

In this work we used a fibrinolysin preparation developed for clinical administration and so recommended by the laboratory. The preparation was dissolved in physiological NaC1, 150 units per ml. The fibrinolysin solutionwas injected into the jugular vein in a dose of 1 ml per 100 g of body weight. The fibrinogen concentration in theblood and the plasma fibrinolytic activity were determined by Bidwells method [4].

Depression of the functioning of the physiological anticoagulatory system in experimental radiation sickness of animals

SummaryExperiments performed on rats demonstrated X-irradiation of animals (600 r) to depress the physiological anticoagulative system. Intravenous administration of thrombin solution (in sufficiently strong concentration) to the irradiated animals caused immediate death from cardiac vessels and vascular thrombosis; this is distinct from normal animals, which being in the same conditions, remained alive. Intravenous injection of thrombin in low doses failed to cause the death of irradiated animals, nor did it provoke protective reaction of the blood fibrinolytic system, but led to a more gradual change of the plasma tolerance of heparin. In 6–10 minutes after thrombin administration (in the same doses) to control animals there is a rise of the blood fibrinolytic activity and a considerable reduction of plasma tolerance to heparin. The data obtained point to the depression occurring in the humoral part of the physiological anticoagulative system in the irradiated animals.