Inactivation of urinary kallikrein by alpha1-antitrypsin

Summary Proteolytic activity, with azocasein as substrate in the presence and absence of 0.4 IU kallikrein (Padutin) was measured in the 24 h urine fractions of 100 ambulatory patients with hypertension, proteinuria or haematuria. Urinary protein and alpha₁-antitrypsin concentration have also been assayed. There was an inverse relationship between kallikrein activity and urinary alpha₁-antitrypsin concentration (r=0.84;y=39.2e^–0.009x). Furthermore, kallikrein activity and 24 h urinary alpha₁-antitrypsin excretion were also inversely correlated (r=0.81;y=886.4e^–0.011x). Our data suggest an inactivation of renal kallikrein by urinary alpha₁-antitrypsin.This work was supported by the Deutsche Forschungsgemeinschaft (Ho 781/3-2)