Endothelial cell surface expression and binding of factor VIII/von Willebrand factor.

Factor VIII/von Willebrand factor (FVIII/vWF), a glycoprotein molecular complex found in human plasma, has been demonstrated by cell membrane fluorescence to be present on the surface of cultured human umbilical cord vein endothelial cells. The endothelial nature of these cells was established by electron-microscopic studies that revealed the presence of Weibel-Palade bodies in virtually all cells cultured. A newly developed radioreceptor assay was used to detect FVIII/vWF in the medium taken from these endothelial cell cultures; FVIII/vWF concentration in the medium samples increased with time in culture. FVIII/vWF binding studies showed no significant FVIII/vWF-specific binding to endothelial cell surfaces and did not corroborate a previous report suggesting a FVIII/vWF-specific receptor on human umbilical cord vein endothelium. The presence of FVIII/vWF on endothelial cell membranes and the lack of receptor-mediated binding suggests that the FVIII/vWF either has been absorbed non-specifically to the cell surface or is an integral part of the endothelial cell membrane.