Inactivation of urinary kallikrein by alpha 1-antitrypsin

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 alpha 1-antitrypsin concentration have also been assayed. There was an inverse relationship between kallikrein activity and urinary alpha1-antitrypsin concentration( r = 0.84; y = 39.2 e-0.009x). Furthermore, kallikrein activity and 24 h urinary alpha 1-antitrypsin excretion were also inversely correlated (r = 0.81; y = 886,4 e-0.011x). Our data suggest an inactivation of renal kallikrein by urinary alpha 1-antitrypsin.