Activation of Factor XII in Rat Plasma: Protection by Benzamidine of the Cofactor Function of High Molecular Weight Kininogen

Publisher Website
Google Scholar
Abstract
Factor XII was assayed as kaolin-activated prekallikrein activator in rat citrated plasma pretreated with acetone. Benzamidine added during blood collection increased the extent of activation by a factor of 6. Rat high MW kininogen (HMWK) added to acetone-treated citrated plasma increased the activation; apparently benzamidine protects the cofactor function of HMWK. All cofactor capacity was retained after the removal of the kinin part of HMWK. Experiments carried out with plasminogen-free plasma showed that plasmin could hardly be the factor responsible for the destruction of HMWK. The stoichiometric factor XII concentration-effect curve obtained by diluting acetone-treated rat plasma with acetone-treated human factor XII deficient plasma showed that factor XII is present in functional excess, the concentration of HMWK deciding the extent of activation. By diluting acetone-treated rat plasma with buffer, HMWK concentration-effect curves were obtained which were approximately linear over a range of 0.03-0.40 .mu.g (bradykinin equivalents)/ml kaolin incubate. No further activation of factor XII was obtained at 0.80 .mu.g/ml.

This publication has 34 references indexed in Scilit: