Thromb Haemostasis
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Human fibrinogen was treated at pH 6.0, 7.3 and 9.0 with thrombin, batroxobin (thrombin-like fraction of Bothrops atrox venom) or an extract of the venom from Ancistrodon contortrix contortrix. These three enzymes released the NH2-terminal fibrinopeptides A and B at different rates. Thrombin-free, preactivated factor XIII (factor XIIIa) was added to incubation mixtures to stabilize resulting fibrin(ogen) aggregates. ⋯ However, when fibrinopeptide B was removed with the contortrix enzyme, soluble cross-linked oligomers appeared initially. The opaque fibrin clots, produced by thrombin (pH 6.0) or contortrix procoagulant fraction (pH 7.3), were found to be devoid of alpha-polymers even after prolonged incubation with factor XIIIa. Our data suggest that the solubility and opacity of fibrin networks are not primarily related to the type of the cross-link (gamma-gamma versus alpha-alpha interactions).