Production of angiotensin converting enzyme by cultured bovine endothelial cells.

1. Endothelial cells from bovine aortae were grown to confluence in tissue culture. The cells were subcultured and angiotensin converting enzyme (ACE) production was measured while the cells were maintained in serum-free medium for 4 days. 2. During this period, there was a ten-fold increase in ACE concentration in the medium whereas the cellular content of the enzyme remained constant at approximately 23% of the total enzyme produced. Cycloheximide (1 mumol/l) blocked production of ACE. 3. The enzyme liberated into the medium closely resembled ACE in the following respects: it cleaved the dipeptide histidyl-leucine from a synthetic tripeptide substrate, was markedly Cl- activated and inhibited by EDTA (1 mmol/l), SQ 14225 (1 mumol/l) or SQ 20881 (1 mumol/l). 4. Cells maintained in culture for up to ten passages have maintained morphology typical of endothelial cells and continue to produce ACE.