Temperature Dependence of Plasmin-Induced Activation or Inhibition of Human Platelets

• Published in: Blood 1991-03, Vol.77 (5), p.996-1005
• Main Authors: Lu, He, Soria, Claudine, Cramer, Elisabeth M., Soria, Jeannette, Maclouf, J., Perrot, Jean Y., Li, Hong, Commin, Pierre L., Schumann, Friedrich, Regnier, Odile, Lijnen, Roger H., Caen, Jacques P.
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal; Biological and medical sciences; Blood coagulation. Blood cells; Blood Platelets - physiology; Blood Platelets - ultrastructure; Cell Degranulation - drug effects; Fibrinogen - metabolism; Fibrinolysin - pharmacology; Fundamental and applied biological sciences. Psychology; Humans; In Vitro Techniques; Microscopy, Electron; Molecular and cellular biology; Platelet Activation; Platelet Aggregation - drug effects; Platelet Aggregation Inhibitors - pharmacology; Platelet Membrane Glycoproteins - immunology; Platelet Membrane Glycoproteins - metabolism; Temperature; Thrombin - pharmacology; Thromboxane B2 - biosynthesis
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V77.5.996.996

It is known that at 37°C plasmin may have two opposite effects on platelets: at high concentrations (>1.5 caseinolytic units [CU]/mL), plasmin activates platelets; at lower concentrations (0.1 to 1.0 CU/mL) it inhibits platelet activation induced by thrombin, collagen, or calcium ionophore A23187. In this study, we report that when lowering the incubation temperature to 22°C, plasmin at low concentrations (0.1 to 0.5 CU/mL) fully activated platelets. When platelets were treated with 0.2 CU/mL of plasmin, lowering the incubation temperature from 37°C to 22°C resulted in an increase in the expression of fibrinogen receptors, in platelet release and aggregation. Thromboxane A2 was not generated by plasmin treatment at either temperature. Ultrastructural studies showed that platelets responded to low-dose plasmin at 37°C by forming pseudopods, centralizing granules without fibrinogen release, whereas at 22°C the same dose of plasmin caused platelet degranulation with the appearance of α-granule fibrinogen within the lumen of the surface connected canalicular system. In addition, at 22°C plasmin at doses insufficient to induce platelet aggregation potentiated platelet response to thrombin. Thus, we suggest that plasmin may initiate both activating and inhibitory processes within platelets and that the change of temperature could influence this balance. These results may be of clinical relevance, because the fibrinolytic system was found activated during cardiopulmonary bypass in which the temperature of patient's blood circulation was reduced. This temperature-dependent behavior is also an interesting model for a further study on platelet response to serine proteinases.