Immunoperoxidase staining for vWf in control and PAF-treated vessels.

(A) Control (untreated) vessels show granular reaction for vWf in the cytoplasm. In addition, vWf is found associated with the endothelial surface, and little reactivity is noticed at the interendothelial cell junctions. (B) In PAF-treated preparations, there is distinct endothelial cell contraction that is indicative of increased venular permeability. Heavy deposits of vWf are seen on the endothelial cell surface and in the interendothelial cell gaps (arrows). Many cells show almost complete depletion of vWf in the cytoplasm (arrowheads).