REGULATION OF ANGIOTENSIN I-CONVERTING ENZYME IN CULTURED BOVINE BRONCHIAL EPITHELIAL-CELLS

The purpose of this study was to determine whether angiotensin 1-conve rting enzyme (ACE) is present in cultured bovine bronchial epithelial cells (BBECs) and whether its activity can be modulated. We found that extracts of confluent monolayers of cultured BBECs degraded [glycine- 1-C-14]hippuryl-L-histidyl-L-leucine at a rate of 843 +/- 66 pmol/hr/m g protein (mean +/- SEM, n = 5). In addition, we found that the enzyme was shed into the culture medium. ACE activity in BBECs was inhibited by three selective, but structurally different, ACE inhibitors (capto pril, quinapril, and cisalaprilat) with an IC50 of approximately 2 nM. Increasing chloride concentration in the assay buffer resulted in an increase in BBECs ACE activity of 63%. Enzyme activity was also modula ted by the presence of zinc cation in the assay buffer. Addition of de xamethasone to the culture medium was associated with a significant in crease in BBECs ACE activity (P < 0.05), which was inhibited by the st eroid receptor antagonist RU 38486. Western blot analysis of BBECs, tr acheal and bronchial mucosal strips utilizing a cross-reacting rabbit anti-mouse ACE antibody, showed a faint 175 kDa band and additional st rong 52 kDa and 47 kDa band. The mechanism of generation of the low M. W. bands is unknown. Our data indicate the presence of ACE in cultured BBECs and that enzyme activity can be modulated. (C) 1993 Wiley-Liss, Inc.