Cold-promoted activation of factor VII in human plasma: studies on the associated acyl-argin?ne esterase activity

Abstract Samples of citrated plasma from untreated normals, women using an oestrogen-containing oral contraceptive, and pregnant women near term were studied regarding activation of factor VII upon cooling at C°C for 18 hours. The samples with markedly shortened thrombotest clotting time also had significantly increased BAEe esterase activity and reduced prekallikrein activity. Concomitantly with the increase in BAEe esterase activity the cooled plasma increased in kininogenase activity and was depleted of kininogen. The esterase and kininogenase activity of cold-activated plasma had the same elution volume upon gel filtration as purified α 2 -macroglobulin-kallikrein complex. Kinetic data also suggested that α 2 -macreglobulin-kallikrein complex is formed during cold activation of plasma. Increased factor XII activity, determined as the prekallikrein-activating capacity, was present in the plasma samples from women using an cestrogen-containing oral contraceptive and from pregnant women near term. Both kallikrein and factor XII may be involved in the cold-promoted activation of factor VII.