von Willebrand factor in lysates of washed canine platelets.

Canine and human platelets (washed 4 times in a solution containing EDTA, prostaglandin E1, and theophylline to prevent release of alpha-granule constituents) were lysed by being frozen and thawed in the presence of detergent. Radioelectroimmunoassay for von Willebrand factor (vWf) in 5 human platelet lysates produced precipitin rockets, shaped like those produced from vWf in plasma from healthy human beings, and indicated that the mean von Willebrand factor antigen (vWf:Ag) content in platelets from healthy human being was 526 +/- 87 human U/10(12) platelets. Radioelectroimmunoassay for vWf in platelet lysates from 17 healthy dogs with normal plasma. vWf:Ag concentration produced precipitin rockets that looked different from those produced from canine plasma and indicated vWf:Ag content of 59 +/- 35 canine U/10(12) platelets. Inclusion of protease inhibitors in the lysing solution did not normalize the appearance of the precipitin rockets or substantially alter the measured platelet content of vWf:Ag. The array of vWf multimers revealed by sodium dodecyl sulfate-agarose gel electrophoresis of canine platelet lysates had a distinct appearance that differed from that of vWf in canine or human plasma and platelets; the intensity of the canine platelet vWf multimer bands was skewed, with relatively greater density in the lower molecular weight region and faint or undetectable multimer bands in the higher molecular weight region. Electrophoretograms with visible multimers in the high molecular weight region had vWf components that had higher molecular weight than did any vWf components in canine plasma. Radioelectroimmunoassay for fibronectin in these same canine platelet lysates indicated that the fibronectin content in platelets was 2.89 +/- 1.10 mg/10(12) platelets.(ABSTRACT TRUNCATED AT 250 WORDS)