Retention of glycoprotein Ib/IX receptors on external surfaces of
thrombin-activated platelets in suspension
JG White, MD Krumwiede, D Cocking-Johnson, GH Rao and G Escolar
Department of Laboratory Medicine, University of Minnesota Medical School,
Minneapolis 55455, USA.
The present study has evaluated the hypothesis stating that glycoprotein
(GP) Ib/IX, the receptor for von Willebrand factor (vWF), is downregulated
and cleared from exposed surfaces to channels of the open canalicular
system (OCS) on platelets activated by thrombin in suspension. Cryosections
of resting and thrombin-activated platelets fixed at intervals of 1 to 30
minutes after stimulation by thrombin and stained with antiglycocalicin
antibody and protein A gold showed no decrease in the density of GPIb/IX
receptors on the platelet surface or increase on linings of the OCS at any
interval after stimulation by thrombin. Thin sections of platelets exposed
to thrombin in suspension followed by settling onto a plastic chamber for
intervals of 1 to 30 minutes revealed retention of GPIb/IX receptors on
exposed surfaces detected by vWF, anti-vWF, and protein A gold throughout
the 30-minute period of study. Results of this investigation indicate that
GPIb/IX receptors remain on the surface of platelets activated by thrombin
in suspension, are not cleared to the OCS, and retain the ability to bind
vWF for at least 30 minutes.
Volume 86,
Issue 9,
pp. 3468-3478,
11/01/1995
Copyright © 1995 by The American Society of Hematology
