Release of plasminogen activator by batroxobin

In the isolated perfused pig ear, batroxobin caused a dose-dependent increase in the release of plasminogen activator. The activator-releasing effect required the presence of the active enzyme. The activator released was of the tissue-type.

Changes of haemostaseological variables in carbon tetrachloride poisoning in rats

On application of carbon tetrachloride to rats disturbances of haemostasis were observed. Antithrombin III and 4-amidinophenylpyruvic acid were found to exert a beneficial action on these disturbances. However, the thrombin inhibitors had no influence on hepatotoxicity and lethality.

Toxicologically relevant disturbances of haemostasis

The normal haemostatic process depends on the normal function of and regular interaction between the vascular wall, the plasmatic coagulation system and the blood platelets. The consequences of interference of chemical compounds with haemostasis are bleeding tendency and bleeding, thrombophilia and thrombosis or disseminated intravascular coagulation. Examples will illustrate that chemicals interfering with haemostasis have different mechanisms and sites of action.

[Pharmacokinetics of 131I-streptokinase]

It has been demonstrated in mouse experiments that 131I-streptokinase undergoes rapid elimination. It has been shown as unfit as a diagnostic agent in the treatment of thromboses.

Characterisation of the vascular plasminogen activator from the pig ear

Spontaneously released plasminogen activator after perfusion with 0.9% NaCl of isolated pig ear was purified by affinity chromatography on Heparin-Sepharose. The molecular weight of the plasminogen activator is about 60,000 Daltons, the isoelectric point lies at pH 7.6. The enzyme is most stable at neutral pH. At 37 degrees C it is stable for two hours. The activator did not show lytic activity either on heated or on PAMBA fibrin plates. The activity of the activator was inhibited by exposure to DFP and PMSF but not by exposure to TLCK and TPCK, suggesting that it is an enzyme with an active-site residue which belongs to the tissue-type activators.

[Effect of phenol ring polymers on the release of plasminogen activators]

The effects of synthetic and natural phenol polymers on the release of plasminogen activator were examined on an isolated vascular preparation of the pig ear. Of the synthetic phenol polymers, the products of caffeine acid and 3,4-dihydroxyphenylacetic acid were found to raise the activity of plasminogen activator. As far as the natural polymers of phenol are concerned, only sodium humate was found to produce an action similar to that of the products of caffeinic acid and 3,4-dihydroxyphenylacetic acid.

Animal experiments on the enhancement of fibrinolytic potential by anabolic steroids

In animal experiments the anabolic steroids 4-chloro-17 beta-hydroxy-17-methylandrosta-1,4-dien-3-one and 4-chloro-11 beta-hydroxy-17-methylandrosta-1,4-dien-3-one were tested for their ability to enhance fibrinolysis in comparison to stanozolol. After daily administration of 2 mg/kg for 12 weeks the anabolic steroids were found to enhance spontaneous fibrinolytic activity of blood, fibrinolytic capacity and tissue plasminogen activator activity in the kidneys of rats and rabbits. Concomitantly, the AT III activity of blood increased.

Chemical control of hyperfibrinolytic states by synthetic inhibitors of fibrinolytic enzymes

The effects of two types of synthetic inhibitor of fibrinolytic enzymes (omega-aminocarboxylic acids, benzamidine derivatives) on intravascular fibrinolysis and fibrinogenolysis were studied in rats. Generalised primary fibrinogenolysis was produced by infusion of human plasminogen-streptokinase complex, secondary fibrinolysis was induced by infusion of the thrombin-like enzyme batroxobin. The inhibitors exerted different effects on the hyperfibrinolytic states. The omega-aminocarboxylic acids (PAMBA, AMCA) inhibited fibrinolysis more effective than fibrinogenolysis. In contrast, the benzamidines (APPA, NANP) were more potent inhibitors of fibrinogenolysis. Aprotinin examined for comparison behaved like the benzamidine derivatives.

[Pharmacokinetic studies with 3H-labelled synthetic antifibrinolytics]

In rabbits and rats pharmacokinetic studies on the anti-fibrinolytics 4-aminomethylbenzoic acid (PAMBA), trans-4-aminomethylcyclohexane-1-carboxylic acid (AMCA), and epsilon-aminocaproic acid (EACA) were carried out using the tritium labelled compounds. Following i. v. administration of PAMBA and EACA in rabbits a two-phasic plasma level and following AMCA a three-phasic plasma level was found within 7 h. The rate constants beta of 0.34 h-1, 0.44 h-1, and 1.08 h-1 for EACA, PAMBA, and AMCA, respectively, indicate a more rapid elimination of AMCA. Accordingly, the AUC-values for AMCA are considerably smaller than those for EACA and PAMBA after both i. v. and p. o. administration.

The use of proteases as thrombolytic agents from the toxicological point of view

In case of systematic hyperproteolysis in the blood of experimental animals after application of ocrase, a fibrinolytically active protease from Aspergillus ochraceus, toxic side effects, particularly on hemostatis and cardiac action, were observed. In order to prevent toxic effects, ocrase in thrombolytic therapy is to be administered within the inhibitor level. After daily administration of 5.6 mg/kg of ocrase (50% of inhibitor level) to rats, toxicological examinations over four weeks showed no deviation from the regular hematological and biochemical values. The thrombolytic effect of ocrase is explained by the formation of an inhibitor-ocrase complex which acts thrombolytically in the presence of fibrin.

Pharmacokinetic studies with 3H-cytisine

The pharmacokinetic behaviour of cytisine was studied in mice by means of tritiated cytisine after intravenous and oral administration of a sublethal dose of 2 mg/kg. After oral administration the maximum blood level is reached after 2 h. The absorption rate is approximately 42%. From the blood level after intravenous administration a half-life of 200 min was calculated. Within 24 h after intravenous administration 32% and after oral administration 18% of the administered radioactivity was excreted into urine. Following intravenous administration 3% of the dose was found in the faeces within 6 h. Among the examined organs and tissues the highest concentrations were reached in the liver, adrenals and kidneys. In the bile the highest concentration after intravenous administration was 200 times that in the blood.

The influence of drugs on the acute toxicity of cytisine

The effect of various drugs on the acute toxicity of cytisine, the toxic constituent of Laburnum anagyroides Med, was studied in mice. Drugs were tested which have been recommended for symptomatic treatment of laburnum poisoning. Drugs which influence the CNS reduce the acute toxicity of cytisine more effectively than those with predominantly peripheral site of action.

[Animal experiments on the pharmacokinetics of ocrase (author's transl)]

The blood level, distribution and elimination of ocrase, a protease from Aspergillus ochraceus, were determined in rabbits after application of the 131I labelled enzyme in therapeutic doses.

[Thrombolytic action of a heparin-ocrase complex]

The thrombolytic action of the complex heparin-ocrase on the experimentally formed fresh thrombi obtained through intravenous introduction of thrombin into an isolated length of the jugular vein was compared against the effect produced on the thrombi by equivalent amounts of individual components of the complex, i.e. heparin and ocrase. Investigations revealed a lysis of experimental fresh thrombi after intravenous injections of the complex heparin-ocrase and this lysis supervened quicker than following the action of equivalent amounts of ocrase. Heparin used in a dose equivalent to its content in the complex did, as this has been presumed, exercise no thrombolytic action at all.