SummaryInfluence of SKPL on platelet function tests has been studied.1. Human platelets suspended in borate buffer lose after SKPL treatment the ability to aggregate under the influence of thrombin, ADP and connective tissue extract.2. Washed platelets incubated with SKPL did not influence the thrombin time of prothrombin free plasma.3. The digestion of platelet rich plasma with SKPL diminished the ability of platelets to aggregate under the influence of thrombin, ADP and connective tissue extract and the adhesiveness to glass.4. Viscous metamorphosis after addition of thrombin or ADP was delayed and less advanced in SKPL treated platelet rich plasma as compared with control undigested plasma.5. The addition of FDP preparation to platelet suspension or to platelet rich plasma impaired their ability to aggregate under the influence of thrombin, ADP and connective tissue extract.6. Adhesiveness of platelets to glass in the whole blood containing FDP was decreased in comparison with controls.7. FDP inhibits also the adhesion of platelets from platelet rich plasma to connective tissue fibers (collagen).8. Viscous metamorphosis induced by thrombin, ADP or connective tissue extract in platelet rich plasma could be delayed or inhibited by addition of FDP.9. Inhibiting effect of FDP on platelet functions were dependent on concentration of FDP and aggregating agent. FDP influence platelet functions in such concentration which inhibit significantly the thrombin time. Increase of the concentration of the inducing agent can overcome the inhibitory effects of FDP.10. The significance of the described findings for the hemostatic function of platelets is discussed.

Summary1. With the aid of isotopie technique, it was shown, that fibrinogen, fibrinogen-fibrin intermediates and fibrinogen degradation products (FDP) may form soluble complexes, which are unclottable by thrombin.2. These complexes may be precipitated by protamine sulphate or by cooling to 4° C (par a coagulation),3. The above findings are discussed in regard to their significance in the pathology of the acute defibrination syndrome :a) Paracoagulation by protamine sulphate without addition of thrombin occurs when defibrination is caused by excessive intravascular clotting, while in cases of the syndrome due to proteolytic digestion of fibrinogen, paracoagulation occurs after combined action of thrombin and protamin sulphate.b) Formation of the complexes described above may explain the occurence of cryofibrinogens in various pathological states.c) Formation of these complexes is postulated to be an important factor involved in the development of the hemostatic defect. It may be as well the expression of a defence mechanism against intravascular fibrin formation by rendering unclottable the intermediates of the fibrinogen-fibrin conversion.

SummaryA hypothesis is put forward according to which the platelet release reaction and viscous metamorphosis are connected with platelet lysosome activation. An essential element of this hypothesis is the assumption of ATPase activation which results in ATP breakdown and ADP release.The following findings are described :1. A variety of agents was studied in regard to their ability to induce the release reaction. It was found that thrombin, trypsin, papaine, elastase, protease from streptomyces griseus, connective tissue “extracts”, contact factor preparations, kaolin suspensions and Triton X-100 induce the release of adenine nucleotides from platelets.2. All the studied release inducing agents activated to some extend the platelet acid phosphatase.3. Streptolysine 0 and staphylocoagulase induce the platelet release reaction as well as the activation of platelet acid phosphatase.4. Agents known to labilize liver lysosomes induce some release of adenine nucleotides from platelets and activate platelet acid phosphatase.5. Prednisolone succinate which is known to stabilize lysosomes, inhibits the activation of acid phosphatase provoked by release inducing agents.6. The activation of liver lysosome acid phosphatase by platelet release inducing agents was irregular and small.7. The ATPase activity of thrombosthenin preparations and of dialysed platelets was found to be increased by thrombin.8. N-ethylmaleimid inhibits the platelet release reaction while ouabaine did not so.The proposed hypothesis is discussed in the light of the recent lysosome research.

Formation of thrombin during incubation of purified bovine prothrombin with purified staphylococcal metalloprotease has been investigated. Thrombin activity was estimated by examination of clotting time and by digestion of a synthetic substrate, Chromozym TH. The metalloprotease caused direct activation of prothrombin which was inhibited by the addition of ethylenediaminetetraacetic acid. Metalloprotease produced by some strains of Staphylococcus aureus may simulate staphylocoagulase activity.

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