Studies on platelets of patients with inherited platelet disorders suggest that collagen-induced fibrinogen binding to membrane receptors requires secreted ADP but not released alpha-granule proteins
Legrand, C.; Nurden, A.T.
Thrombosis and Haemostasis 54(3): 603-606
1985
ISSN/ISBN: 0340-6245 PMID: 3003952 Document Number: 246466
Collagen induces a saturable 125I-fibrinogen binding to normal human platelets. A role for secreted ADP in this process is supported by studies on 2 patients with the Chédiak-Higashi syndrome. Both collagen-induced nucleotide release and 125I-fibrinogen binding were strongly reduced while ADP-induced fibrinogen binding was normal. Platelets from 2 patients with the gray platelet syndrome bound normal amounts of 125I-fibrinogen in the presence of ADP or collagen despite the severe reduction of secretable alpha-granule proteins. Binding did not occur to collagen-stimulated type I thrombasthenic platelets which lacked GPIIb-IIIa complexes but was detected in amounts which correlated with the residual concentrations of GPIIb-IIIa in the platelets of a patient with type II disease. Our results allow us to propose that collagen-induced fibrinogen binding to normal platelets requires the presence of GPIIb-IIIa complexes and secreted ADP but proceeds independently of alpha-granule release.