Role of peptidases in bradykinin-induced increase in vascular permeability in vivo.

The purpose of this study was to examine whether neutral endopeptidase and angiotensin I-converting enzyme, two membrane-bound metalloenzymes that are widely distributed in the microcirculation, play a role in bradykinin-induced increase in vascular permeability in the hamster cheek pouch. Changes in vascular permeability were quantified by counting the number of leaky sites and by calculating the clearance of fluorescein isothiocyanate (FITC)-dextran (molecular mass, 70,000 d) during suffusion of the cheek pouch with bradykinin. Bradykinin produced a concentration- and time-dependent increase in the number of leaky sites and clearance of FITC-dextran. The selective, active site-directed neutral endopeptidase inhibitors phosphoramidon (1.0 microM) and thiorphan (10.0 microM) and the selective angiotensin I-converting enzyme inhibitor captopril (10.0 microM) each shifted the concentration-response curve to bradykinin significantly to the left. During suffusion with bradykinin (1.0 microM) and phosphoramidon, the number of leaky sites increased significantly from 17 +/- 2 to 27 +/- 4 sites per 0.11 cm2 (mean +/- SEM, p less than 0.05), and FITC-dextran clearance increased significantly from 1.0 +/- 0.2 to 2.1 +/- 0.3 ml/sex x 10(-6).(ABSTRACT TRUNCATED AT 250 WORDS)