Direct radioimmunoassay for rat high molecular weight kininogen. Measurement of immunoreactive high molecular weight kininogen in normal and kininogen deficient plasma.

A direct radioimmunoassay (RIA) for rat high molecular weight kininogen (HMW Kg) was developed that enabled us to detect 71 fmol/ml of HMW Kg. The antibodies did not crossreact in the RIA with up to 5 nmol of purified rat alpha 1 cysteine proteinase inhibitor (T-kininogen). When various quantities of pure HMW Kg were either quantified by the RIA or by the measurement of kinin contents determined after trypsin hydrolysis, identical values were obtained by both methods. This RIA allowed the measurement of HMW Kg in 0.015 to 1 microliter of rat plasma. HMW Kg levels in plasma of Wistar rats and in Brown Norway rats of the Orlean Strain (BN/Orl) were 1.52 +/- 0.05 (n = 6) and 2.050 +/- 0.015 (n = 8) nmol/ml respectively. In the Brown Norway rats of the Katholiek strain (BN/Kat) that are considered to be deficient in HMW Kg, immunoreactive HMW Kg levels were less than 2% of those of the BN/Orl rats. These results confirm that the BN/Kat animals have a molecular defect in HMW Kg.