A Micromethod for the Determination of Bradykininogen in Blood Plasma

Abstract

BRADYKININOGEN is the inactive precursor from which bradykinin, the hypotensive and smooth-muscle stimulating nonapeptide, can be released by the action of trypsin¹. The concentration of the precursor in blood can be evaluated by the amount of bradykinin liberated by the action of trypsin on known volumes of plasma. The main difficulty found in a procedure for the determination of bradykininogen is the presence of trypsin inhibitors which interfere with the release of bradykinin, and the presence of enzymes which inactivate it in fresh plasma. This difficulty can be overcome if the plasma is previously heated in boiling water in the presence of diluted acetic acid, in order to obtain a denatured substrate. By this procedure trypsin inhibitors and bradykininolytic enzymes are inactivated^2,3.