Determination of Bradykinin in Blood by a Sensitive Radioimmunoassay

Abstract

Antibodies of high avidity (maximum Km 1.3 × 10¹⁰ L/M) were produced in rabbits against bradykinin coupled to ovalbumin with toluene-2,4-diisocyanate. Tyrosin⁸ bradykinin was labelled to a specific activity of 530–700 Ci/mmol with ¹²⁵I by means of lactoperoxidase. Sensitivity of the radioimmunoassay was 0.01 μg/1 blood. Specificity studies demonstrated the essential role of the C-terminal arginine of bradykinin for binding to antibody. Mean recovery of [³ PHJbradykinin internal standard after the preparation of 86 blood samples was 39.0%. The major loss occurred during ethanol precipitation. In venous blood collected at random conditions from 32 normal subjects the bradykinin concentration ranged 0.04–0.46 μg/1 and showed no sex difference.