DETERMINATION OF VITAMIN-K SENSITIVE COAGULATION-FACTORS IN PLASMA - STUDIES ON 3 METHODS USING SYNTHETIC CHROMOGENIC SUBSTRATES

Methods used for monitoring coumarol treatment should be sensitive to the loss of calcium binding γ-carboxyl glutamic acids in the prothrombin or factor X molecules. In this study determinations of generated enzymatic activity has been performed by means of chromogenic oligopeptide synthetic substrates: Bz-Ile-Glu-Gly-Arg-pNA sensitive to factor Xa and H-D-Phe-Pip-Arg-pNA sensitive to thrombin. Two activating principles have been investigated, Russel viper venom (RVV), and the venom from Echis carinatus (Ecarin). When a substrate specific for thrombin was used to measure the activity generated after RVV-lipid activation a method sensitive to factors II, V and X was obtained. When using RVV without lipid and a substrate specific for factor Xa, however, the method was specific for factor X. These two methods were both sensitive to the coumarol induced defect and correlated well with the Thrombotest method when tested on coumarol plasmas (r = 0.85 and r = 0.84, respectively). The activity generated by Ecarin was registered on a thrombin sensitive substrate. This method was specific to prothrombin but was less sensitive to the coumarol induced prothrombin defect and resulted in a noncorrelated relation to Thrombotest using coumarol plasma. It is suggested to use the factor X specific method for monitoring coumarol treatment. The specificity and reproducability of this method is better than for the clotting techniques. In addition this method is a more accurate enzymatic determination which is easily automized. © 1978.