A model for the in vivo clearance of normal and mutant forms of human
von Willebrand factor (VWF) has been established using catheterized ra
ts, vWF clearance rates in rat plasma were determined by quantitation
of reduced vWF subunits on sodium dodecyl sulfate-polyacrylamide gel e
lectrophoresis (SDS-PAGE), and multimeric vWF was analyzed using nonde
naturing SDS-agarose gels, Normal vWF derived from human umbilical vei
n endothelial cells displayed a biphasic pattern of clearance, with ha
lf times of 35 minutes (T-1/2 a; SD 15. min.) and 245 minutes (T-1/2 b
; SD 76. min.); metabolic clearance rate = 0.65%/minute. High molecula
r weight multimers of vWF were cleared more rapidly than dimeric vWF,
vWF containing the S1613P mutation found in some type 2A von Willebran
d disease (vWD) patients was observed to undergo proteolysis in vivo r
esulting in a reduction of high molecular weight vWF and concomitant a
ppearance of rapidly-migrating satellite species, although the overall
clearance rate of vWF antigen was similar to wild type vWF, These res
ults provide direct in vivo evidence that the S1613P mutation causes t
he characteristic type 2A vWD phenotype, Full-length recombinant vWF p
roduced from transfected Chinese hamster ovary cells was cleared at a
similar rate to endothelial cell-derived vWF, and recombinant vWF devo
id of O-linked carbohydrates was cleared significantly faster, vWF dev
oid of sulfate was cleared at a similar rate as wild type vWF, indicat
ing the sulfate moiety of vWF does not regulate in vivo clearance, Thi
s animal model should prove useful in subsequent in vivo analysis of a
dditional forms of vWD and in the development of protease inhibitor th
erapy for 2A vWD. (C) 1996 by The American Society of Hematology.