LOCALIZATION OF FIBRIN CONVERTED BY THROMBIN FROM RELEASED PLATELET FIBRINOGEN

  • 1 January 1980
    • journal article
    • research article
    • Vol. 55  (2) , 187-194
Abstract
Treatment of [human] platelets (109 cells/ml) with thrombin (1 U[units]/ml) resulted in rapid disappearance of fibrinogen from the system as measured by the tanned red cell hemagglutination inhibition immunoassay (TRCHII). Plasmin digestion of individual pellet and supernatant fractions was previously separated from thrombin-treated platelet suspensions by centrifugation resulted in recovery of TRCHII-detectable material in platelet pellets. To elucidate the specific association of fibrin to platelet membranes, control and thrombin-treated platelets were homogenized by a modified glycerol loading and N decompression technique. Ultracentrifugation of homogenates through 27% sucrose cushions yielded 3 subcellular fractions: supernatant, small membrane vesicles and a particulate fraction for controls; and supernatant membrane vesicles, and aggregated membrane ghosts for thrombin preparations. Ultrastructurally identifiable fibrin was noted only in the thrombin fraction containing membrane ghosts. Fibrinogen recovered from 3 thrombin fractions was markedly decreased (3% of the control). Plasmin digestion produced 23% and 46-fold increase in TRCHII-detectable material from 3 subcellular fractions of control and thrombin preparations, respectively. More than 97% of TRCHII material recovered from thrombin preparations was in the fraction containing aggregated membrane fractions. Platelet plasma membranes apparently function as surfaces for fibrin deposition.

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