[The vasomotor effects of the enzymes of the fibrinolytic system in rats]. / Vazomotornye éffekty fermentov fibrinoliticheskoi sistemy krys.

Human plasmin (Pm) caused a rapid dose-dependent relaxation of norepinephrine-preconstricted isolated aortic ring and vascular net in the Wistar rat hindlimbs. Neither atropine, nor obsidan or indomethacin suppressed the Pm-induced vasodilatation of the aortic ring. Mechanical removal of endothelium and NO-blocker N-Nitro-L-Arg almost completely abolished the Pm-induced relaxation. DIP-Pm, AN-Pm and Glu-plasminogen did not change the vascular tone of the preconstricted rings. Both aprotinin and E-aminocapronic acid inhibited the relaxing effect of the Pm. Besides the circulating Pm, the enzyme forming on the endothelial surface from plasminogen under the action of urokinase, produced the vascular dilatation as well.

[The effect of the joint administration of heparin and chitosan sulfate ether on hemostatic function]. / Vliianie sovmestnogo vvedeniia geparina i sernokislogo éfira khitozana na funktsiiu gemostaza.

We studied anticoagulant effects of combined administration of heparin (H) and chitosan sulfate ether (CS) (specific activity 20 UE/mg) in the ratio 1 : 1. CS enhanced anticoagulant activity of heparin in rabbits by a factor of 1.95 +/- 0.15. The intravenous injection of the mixture in a dose of 0.5 mg(H)/kg + 0.5 mg(CS)/kg and heparin injection in a dose of 1mg/kg induced the same effect. Haemorrhagic effect of this mixture was less pronounced compared to heparin, anticoagulant and antithrombotic activities remained the same. The mixture was found to decrease a number of platelets, however, this was also less pronounced compared to heparin. Thus, the use of the mixture CS + H (1 : 1) instead of double heparin dose resulted in the same effect.

Collagen-targeted antibodies inhibit platelet-dependent thrombosis in vivo.

Subendothelial collagen is one of the main triggers of platelet-dependent thrombus formation in arteries. The antithrombotic effects of rabbit polyclonal inhibitory antibodies to rat collagen type I-III and of murine non-inhibitory monoclonals to human recombinant single-/two-chain urokinase-type plasminogen activator (rscu-/rtcu-PA), cross-reacting with rat scu-/tcu-PA and their chemically synthesized conjugate, were studied both in vitro and in vivo. Anticollagen antibodies and bispecific conjugate inhibited human platelet adhesion, aggregation and formation of thrombus-like structures induced by rat collagen immobilized on the polystyrene surface in a condition mimicing a high shear rates in the large elastic arteries. Monoclonals to human rscu-/rtcu-PA did not block the collagen-induced platelet activation in vitro. The short-term treatment of the collagen-soaked silk thread by the collagen antibodies suppressed the platelet-dependent thrombus formation in the arterio-venous shunt in rats by 56 +/- 4% (P < 0.05). Bispecific conjugate, directed to collagen and endogenous rat scu/tcu-PA inhibited thrombus formation by the same factor as anticollagen antibodies. The treatment of collagen-adsorbed conjugate by human rtcu-PA did not increase the antithrombotic effect. The present results suggest, that the local administration of the anticollagen antibodies to the site of vascular injury can be an efficient tool for prophylaxis of platelet-dependent thrombus formation in arteries at thrombolysis or percutaneous transluminal coronary angioplasty.

[The antithrombotic action of a protein C activator from the venom of Agkistrodon blomhoffi ussuriensis in thrombus formation in an extracorporeal shunt in rats]. / Antitromboticheskoe deistvie aktivatora proteina C iz iada Agkistrodon blomhoffi ussuriensis pri tromboobrazovanii v ékstrakorporal'nom shunte u krys.

An antithrombotic action of the protein C (PC) activator from the venom of Agkistrodon blomhoffi ussuriensis on the model of platelet-dependent thrombosis in the arteriovenous shunt in rats was under investigation. Administration of the PC activator to rats resulted in a dose-dependent prolongation of the thrombus formation time, in a decrease in PC and factor V levels in blood and in APTT prolongation. There were no changes in the tissue-type plasminogen activator level and in the ADP- or epinephrine-induced platelet aggregation, but platelet adhesion to glass decreased. The possible mechanism of the antithrombotic action of the PC activator appeared to be the factor V inactivation mediated by protein C activation and the decrease in platelet adhesion.

Role of sympathetic cholinergic pathway in the neurogenous control of tissue-type plasminogen activator release into the blood.

The changes in conductivity of skeletal muscle vessels of the hind leg and tissue-type plasminogen activator (t-PA) activity in outflowing blood after electrostimulation (5 V, 0.5 ms, 20 Hz, 30 s) at the L4-L5 level of the peripheral end of the transected isolated sympathetic chain were studied in experiments on anaesthetized cats. Stimulation of the sympathetic chain induced vasoconstriction and release of t-PA from the vascular wall into the blood. Pretreatment with the beta-adrenoblocker propranolol neither changed the character of vascular reactions nor blocked t-PA secretion. Efferent stimulation of the sympathetic chain against a background of alpha-adrenoceptor blockade by dihydroergotoxin increased blood flow and was accompanied by a rise in t-PA activity. The M-cholinergic blocker atropine suppressed both vascular relaxation and release of t-PA into the blood. Vasodilatation accompanied by t-PA secretion could be induced by intraarterial infusion of acetylcholine and blocked by atropine. The existence of a neurogenic mechanism controlling t-PA release from the vascular wall involving a sympathetic cholinergic pathway and connected with excitation of vascular M-cholinoceptors by acetylcholine is suggested.

Protein C activator from the venom of Agkistrodon blomhoffi ussuriensis retards thrombus formation in the arterio-venous shunt in rats.

Protein C (PC) is an anticoagulant protein which, being activated by thrombin, degrades factors V/Va and VIII/VIIIa and releases a tissue-type plasminogen activator. Some Agkistrodon snake venoms contain PC activators which, in experiments, exert an anticoagulant action. An antithrombotic effect of the PC activator from the venom of A. blomhoffi ussuriensis on the model of thrombus formation in the arterio-venous shunt in rats was under investigation. Administration of the PC activator resulted in a dose-dependent prolongation of the thrombus formation time and a decrease in plasma PC activity, which were accompanied by a decrease in factor V activity and APTT prolongation. No reliable changes in the t-PA level, ADP- and epinephrine-induced platelet aggregation were observed. Platelet adhesion to glass beads diminished. We assume that the antithrombotic effect of the PC activator from the A. blomhoffi venom in the platelet-dependent thrombosis model is caused by PC activation and subsequent factor V inactivation as well as by platelet adhesiveness reduction.

[Mechanisms of anticoagulant effect of chitosan sulfuric acid ester]. / Mekhanizmy antikoaguliantnogo deistviia sernokislogo éfira khitozana.

Anticoagulation effect of chitosan sulfate ester and some mechanisms of its influence on hemostasis were studied in vitro. The chitosan sulfate ester catalyzed more effectively inactivation of the enzymes involved in the inner pathway of blood coagulation affecting only slightly the activity of outer pathway factors. The ester, similarly to heparin, inhibited blood coagulation mainly via accelerated thrombin inactivation by means of blood plasma antithrombin III. Inhibition of the enzyme coagulation activity using heparin cofactor II occurred only at high concentrations of chitosan sulfate ester in blood plasma. Besides, the ester decreased the thrombin catalytic activity in reactions with natural and synthetic peptide substrates. Thus, anticoagulation effect of chitosan sulfate ester is similar to that of heparin.

[The role of heparin and tissue-type plasminogen activator in the adaptation of the hemostatic system to high altitude]. / Rol' geparina i aktivatora plazminogena tkanevogo tipa v adaptatsii sistemy gemostaza k usloviiam vysokogor'ia.

The role of endogenous heparin and tissue-type plasminogen activator in the middle-period (25 days) adaptation of haemostasis to high altitude (altitude 3200 m) and formation or "high-altitude hypocoagulation" was studied in the experiments on white rats. It was observed that the formation of "high-altitude hypocoagulation" is connected with an increase of heparin and tissue-type plasminogen activator level due to its release from must and endothelial cells to the bloodstream. Histochemical analysis showed that at the course of adaptation to high altitude the increase in blood heparin level was caused by the stimulation of must cells secretory activity. The endothelium of lung vessels is the main source of tissue-type plasminogen activator release into the blood. The existence of interconnection between the changes in haemostasis and stimulation of angiogenesis at high altitude is proposed.

[The thrombolytic activity of acylated activator complexes of plasmin-streptokinase with different rates of reactivation]. / Tromboliticheskaia aktivnost' atsilirovannykh aktivatornykh kompleksov plazmin--streptokinaza s razlichnymi skorostiami reaktivatsii.

In the experiments on guinea-pigs with venous thrombosis there were studied the fibrin- and thrombolytic effects of streptokinase, the plasmin-streptokinase complex and the acylated derivatives of the complex with various rates of reactivation. It was established that the acylated derivatives of the plasmin-streptokinase complex possess greater stability in the blood flow and lead to more prolonged stimulation of fibrinolysis at less magnitude of its systemic activation. Due to this the acylated derivatives of the plasmin-streptokinase complex produce less pronounced fibrinogenolysis. In connection with a high affinity to fibrin their thrombolytic action does not depend on the systemic activation of fibrinolysis.

[Effectiveness of acylated thrombolytic agents in lysis of blood plasma clots from humans and various animals]. / Effektivnost' atilirovannykh tromboliticheskikh agentov v lizise sgustkov iz plazmy krovi cheloveka i zhivotnykh razlichnykh vidov.

Kinetics of lysis of fibrin clots from the human, guinea pig, rat and rabbit blood plasma by two active-site-acylated derivatives of the activator plasmin-streptokinase complex with different reaction rate constants has been studied in vitro. It is found that lysis of blood plasma clots in guinea pig is most similar to that of man. Acyl activator dose being increased, the lysis of a plasma clot in guinea pig is accelerated. Two acyl activators exhibit higher fibrinolytic-efficiency as compared to a free activator. Experiments carried out in vivo on guinea pigs with thrombosis show that acyl activators, in contrast to nonmodified plasmin-streptokinase complex induce the less system activation of fibrinolysis and the less fibrinogenolysis.

[Disorders of thrombin interaction with the blood vessel wall and its inactivation by antithrombin III in experimental nephrotic syndrome]. / Narushenie vzaimodeistviia trombina s sosudistoi stenkoi i ego inaktivatsii antitrombinom III pri éksperimental'nom nefroticheskom sindrome.

In the experiments on white rats was conducted a comparative study of 125I-alpha-thrombin clearance and its inactivation by antithrombin III in animals of the control group and rats with the experimental nephrotic syndrome (Heymann nephritis). It was determined that alterations of thrombin binding to the vascular wall in the nephrotic syndrome induced the prolongation of the labelled enzyme half-life in the blood stream. The formation of 125I-alpha-thrombin complexes with antithrombin III was delayed in the nephrotic syndrome, that suggests the violation of mechanisms of thrombin inactivation by antithrombin III. The distortions of endothelium-mediated thrombin elimination and inactivation in the nephrotic syndrome resulted in the enzyme interaction with fibrinogen, which threatened organism by thrombosis.

[The stimulation of fibrinolysis during cholinergic vasodilating reactions]. / Stimuliatsiia fibrinoliza pri kholinergicheskikh sosudorasshiriaiushchikh reaktsiiakh.

Changes in the fibrinolytic activity of blood flowing from the skeletal muscles during electrostimulation of the peripheral end of the cut-off sympathetic chain at the blockade of alpha-adrenoceptors have been studied in the acute experiments on cats. It is stated, that this action induces not only an increase of vascular conductivity but also fibrinolysis stimulation relating to the secretion of plasminogen activators to the blood. The effect of fibrinolysis stimulation was reproduced during intraarterial infusion of acetylcholine and was blocked by atropine. The vasodilating reactions on sodium nitroprusside and papaverine similar by intensity to the cholinergic reactions induce no plasminogen activator release. The existence of the specific regulation mechanism of plasminogen activator secretion, mediated by M-cholinoceptors is suggested.

[Heterogeneity of mammalian antithrombin III]. / Geterogennost' antitrombina III mlekopitaiushchikh.

Affinity chromatography on heparin-Sepharose was used to isolate two forms of antithrombin III(AT) from human, bovine, rabbit and rat blood plasma. The two isolated forms of AT are the major form. AT alpha, making up to 90% of the whole inhibitor molecule, and the minor form, AT beta (10% of AT). The molecular mass of AT beta in all mammalian species under study is by 3-5 kDa lower than that of AT alpha. The isoelectric point for bovine AT alpha lies within the range of 4.95-4.5, whereas that for AT beta--at 5.28-4.76. No significant differences in the progressive antithrombin activity of the major and minor forms of the bovine inhibitor were observed. In contrast, the heparin-cofactor activity of the AT beta-heparin complex exceeds that of the AT alpha-heparin complex--3-fold. The functional differences in the AT forms are due to the differences in their affinities for heparin. It was shown that AT beta exhibits a higher affinity for free and bound heparin.

[The role of the active center of the enzyme in the triggering mechanism of the compensatory reaction to plasmin]. / Rol' aktivnogo tsentra fermenta v trigernom mekhanizme kompensatornoi reaktsii na plazmin.

The participation of plasmin active site in the trigger's mechanisms of the compensatory reaction of haemostasis system on this enzyme was studied in the experiments on white rats and rabbits using intravenous injection and perfusion of the humorally isolated carotid sinus are with intact innervation. Native enzyme, the enzyme with reversibly (acylated plasmin) and irreversibly (diisopropylphosphoryl plasmin) blocked active site were used. It was ascertained that the development of the compensatory reaction of haemostasis system on plasmin, manifested by hypercoagulation and depression of fibrinolysis, is conditioned by the proteolytic activation of the vascular wall receptors.

[Anticoagulant and antithrombotic effects of low molecular weight heparin]. / Antikoaguliantnye i antitromboticheskie éffekty nizkomolekuliarnogo geparina.

Low molecular weight heparin (Mr 8 kDa) was prepared from conventional heparin (Mr 18 kDa) by the chromatography on DEAE-sephadex with the recovery of 56%. Low molecular weight heparin had less affinity to antithrombin III than unfractionated heparin and had less anticoagulant and anti-IIa activities. The anti-Xa activity of low molecular weight heparin exceed by 17% the activity of conventional heparin. In the experiments on rats it was determined that the biological half-life of low molecular weight heparin exceed two-fold that of the unfractionated heparin. In the modified model of the arteriovenous shunt thrombosis in normal and nephrotic syndrome rats it was shown that the low molecular weight heparin was the most efficient antithrombotic remedy in normal and decreased level of antithrombin III in the organism.