Major amount of angiotensin I is conveed to angiotensin II in:

The lungs also activate one hormone; the physiologically inactive decapeptide angiotensin I is conveed to the pressor, aldosterone-stimulating octapeptide angiotensin II in the pulmonary circulation. The reaction occurs in other tissues as well, but it is paicularly prominent in the lungs. Large amounts of the angiotensin-conveing enzyme responsible for this activation are located on the surface of the endothelial cells of the pulmonary capillaries. The conveing enzyme also inactivates bradykinin. Circulation time through the pulmonary capillaries is less than 1 s, yet 70% of the angiotensin I reaching the lungs is conveed to angiotensin II in a single trip through the capillaries. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 35.