Kinins and angiotensins. Angiotensin I converting enzyme (kininase II) in endothelial cells cultured from human pulmonary arteries and veins.

Human pulmonary endothelial cells were used to study the metabolism of angiotensin I and bradykinin by angiotensin I converting enzyme (kininase II; ACE). The endothelial cells cultured from pulmonary arteries and veins differed with respect to their enzyme activity and their surface structure, as viewed with scanning electron microscopy. Cells from adult pulmonary arteries had greater ACE activity than cells from either adult pulmonary veins or fetal pulmonary arteries. In addition, cells from adult pulmonary arteries exhibited more prominent surface projections than cells from veins or fetal pulmonary arteries. A brief exposure to trypsin decreased the ACE activity in cells from arteries but not in cells from veins. Possible the differences in ACE activity between these cells are related to their surface structures.