Summary
Von Willebrand factor (vWf), a multimeric adhesive glycoprotein synthesized, stored,
and secreted in megakaryocytes and endothelial cells, is normally found in plasma,
platelets and subendothelium. While many substances mediate the release of vWf from
endothelial cells, factors that enhance vWf synthesis and partitioning to its regulated
pathway are currently unknown. We studied the effect of pharmacologic doses of heparin
on the vWf content of endothelial cells. After a lag of 8 h and in the presence of
crude or purified growth factor, heparin at doses between 0.25 and 2 U (1.4-11 μg)/ml,
increased the content of high moleculr weight vWf. The increased amounts of vWf were
localized to Weibel-Palade bodies and extracellular matrix. Lower molecular weight
highly sulfated heparin or heparin-like compounds were most active in growth factor
dependent endothelial cell vWf expression. There was no clear importance of polysaccharide
sequence or protein core.
