Venom coagglutinin: an activator of platelet aggregation dependent on von Willebrand factor.

Abstract

A platelet-aggregating activity was found in many snake venoms, predominantly those of the genus Bothrops, that was apparent only in the presence of the platelet-aggregating von Willebrand factor of plasma. It was designated venom coagglutinin. The coagglutinin could be largely separated from the thrombin-like enzyme of the venoms by ion-exchange chromatography. The venom factor acted on formaldehyde-fixed platelets and was effective with decalcified, heparinized and afibrinogenemic plasmas but not with severe von Willebrand disease plasmas or with normal plasmas in which the von Willebrand factor was neutralized by specific antibodies. Use of this coagglutinin permitted the assay of von Willebrand factor without the many disadvantages of the ristocetin test. The coagglutinin was active with human, dog, pig and bovine plasmas and with platelets of any one of these species. This broad-spectrum activity without regard to species contrasted with the ristocetin-resistance of many combinations of plasma and platelets from various species. The assay provides a procedure for studying human, porcine and canine von Willebrand disease. The lack of species specificity of the coagglutinin suggests it may be a universal activator of the von Willebrand factor-platelet reaction.