Changes in high molecular weight kininogen levels during and after cardiopulmonary bypass surgery measured using a chromogenic peptide substrate assay.
High molecular weight kininogen (HK) is a co-factor in the blood-contact activation system. A chromogenic peptide substrate assay for HK (HKcs) has been developed in which test plasmas are mixed with diluted HK-deficient plasma and incubated with a soluble contact system activator that activates prekallikrein and factor XII. Calcium chloride, a synthetic thrombin inhibitor and a chromogenic peptide substrate for activated factor X (FXa) are then added. The FXa generated cleaves the FXa substrate releasing p-nitroanaline, which is measured photometrically. Test plasma HK values were calculated from a standard curve generated using a pooled normal plasma. Acceptable intra-assay and inter-assay precision values were obtained and levels of HK up to 200% were measurable. The assay measured HK in plasmas deficient in factor XII, prekallikrein and factor XI, was not affected by antiphospholipid antibodies and gave an acceptable correlation (r = 0.95) when normal plasmas and mixtures of HK-deficient and normal pooled plasma, calculated to give HK levels of 25 and 50%, were compared using HKcs and a HK one-stage clotting assay. The HKcs was used to measure HK levels in seven patients undergoing cardiopulmonary bypass (CPB). HK levels fell significantly during CPB (P = 0.0014) and were significantly higher (P = 0.016) 6 days after CPB, suggesting that HK may be a positive acute-phase reacting protein.
Kent Haemophilia Centre, Kent and Canterbury Hospital, UK. mikejgallimore@aol.com
M J
MJ
Gallimore
D W
DW
Jones
M
M
Winter
H P
HP
Wendel
D000209:Acute-Phase Proteins; D000328:Adult; D017152:Antibodies, Antiphospholipid; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D002863:Chromogenic Compounds; D005174:Factor XII / Q000378:metabolism; D015951:Factor Xa / Q000378:metabolism; D005260:Female; D006801:Humans; D019679:Kininogen, High-Molecular-Weight / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010455:Peptides; D012015:Reference Standards; D012016:Reference Values; D015203:Reproducibility of Results; D013057:Spectrum Analysis
D000209:Acute-Phase Proteins; D017152:Antibodies, Antiphospholipid; D002863:Chromogenic Compounds; D019679:Kininogen, High-Molecular-Weight; D010455:Peptides; D005174:Factor XII; D015951:Factor Xa