Ultrastructural analysis of the distribution of von Willebrand factor and fibrinogen in platelet aggregates formed in the PFA-100.
1. Platelets. 1998;9(6):381-9.
Ultrastructural analysis of the distribution of von Willebrand factor and
fibrinogen in platelet aggregates formed in the PFA-100.
Poujol C(1), Nurden A, Paponneau A, Heilmann E, Nurden P.
Author information:
(1)UMR 5533 CNRS, Hôpital Cardiologique, Pessac, France.
The PFA-100 is a new apparatus used to detect platelet dysfunction in vitro .
Anticoagulated blood flows under constant pressure through a capillary, and
across an aperture that pierces a membrane coated with collagen and either
epinephrine or ADP. Through their ability to adhere and aggregate, platelets
occlude the orifice and the closure time is a test of platelet function. Using
electron microscopy and immunogold staining, we have analyzed the ultrastructure
of platelet aggregates formed within the aperture and that are responsible for
the occlusion. Standard electron microscopy showed that the aggregates formed on
both collagen-epinephrine and collagen-ADP cartridges presented the same
morphological features. The aggregates were exclusively composed of platelets,
some of which were degranulated. Degranulation was particularly intense at the
periphery of the aggregate where platelets were often totally devoid of secretory
organelles. Immunogold staining on ultrathin frozen sections with polyclonal
antibodies, allowed us to evaluate the distribution of adhesive proteins such as
fibrinogen and von Willebrand factor (vWF) within the aggregate. The latter was
found to be abundant in the intercellular spaces between adjoining platelets.
Although fibrinogen was also present, its labeling was less intense suggesting
that vWF is the major protein implicated in the platelet-platelet interactions in
the aggregates formed in the PFA-100 system. This may be because of the high
shear rate that occurs across the aperture which suggests that the PFA-100 is
particularly sensitive for detecting abnormalities of vWF-platelet interactions.
DOI: 10.1080/09537109876456
PMID: 16793722