Aging of endothelium in culture: Decrease in angiotensin-converting enzyme activity

Abstract An examination of angiotensin-converting enzyme (ACE) activity in cultured endothelium revealed a decrease in the specific activity of the enzyme as the population doubling level of the cultures increased. This observation does not extend to all plasma membrane enzymes. When 5′-nucleotidase activity in endothelial cells was examined, late passage cells showed a marked increase in activity when compared to early passage cells. The decrease in ACE activity may represent an important functional change in the aging endothelial cell population.