The effect of thrombin on the dynamic exchange between intraplatelet and extraplatelet fibrinogen.
We examined the distribution of platelet fibrinogen and the exchange between intra- and extra-platelet fibrinogen in unstimulated and thrombin-stimulated platelets. In unstimulated platelets 60% of platelet fibrinogen was found in the soluble platelet fraction and 40% in the insoluble one. In platelets activated with thrombin, changes took place in the distribution of intraplatelet fibrinogen but not in the total fibrinogen content. At > or = 0.5 U/ml of thrombin the fibrin(ogen) content of the insoluble and soluble fractions was approximately 80% and 20%, respectively. When we evaluated how extraplatelet fibrinogen affects the content and distribution of intraplatelet fibrinogen, we found that when unlabelled fibrinogen was added to unstimulated and thrombin-stimulated platelets the content and distribution of intraplatelet fibrinogen remained unaltered. However, when 125I-fibrinogen was added, it was incorporated into unstimulated and thrombin-stimulated platelets. In unstimulated platelets, 70% of the incorporated 125I-fibrinogen was in the soluble fraction and 30% in the insoluble. In thrombin-stimulated platelets the distribution of the incorporated 125I-fibrinogen was 62% and 38% in soluble and insoluble fractions respectively. MoAb to GPIIb-IIIa produced 80% and 60% inhibition of 125I-fibrinogen incorporation by unstimulated and thrombin-stimulated platelets. Our data showed dynamic exchange between intraplatelet and extraplatelet fibrinogen both in unstimulated and thrombin-stimulated platelets mediated mainly by GPIIb-IIIa.
Vila
V
V
Research Centre, University Hospital La Fe, Valencia, Spain.
Martínez-Sales
V
V
Réganon
E
E
Aznar
J
J
D001792:Blood Platelets / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D005344:Fibrinopeptide A / Q000378:metabolism; D006801:Humans; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000502:physiology; D013917:Thrombin / Q000378:metabolism*
D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005344:Fibrinopeptide A; D005340:Fibrinogen; D013917:Thrombin