Why is angiotensin converting enzyme localized in the lungs
ACE is present on the luminal surface of vascular endothelia throughout the body and is abundantly present in the endothelium-rich lungs. 

ACE in the kidney—particularly in the endothelial cells of the afferent and efferent arterioles—
can produce enough ANG II to exert local vascular effects. 

Thus, the kidney receives ANG II from two sources: 

✓ Systemic ANG II comes from the general circulation and originates largely from the pulmonary region, and 

✓ Local ANG II forms from the renal conversion of systemic ANG I. 

• In addition, the proximal tubule secretes ANG II into its lumen and thus achieves intraluminal concentrations in excess of
those in the general circulation. ANG II in the circulation has a short half-life (~2 min).