An impoant non-respiratory function of Lungs is:

Lung has large amounts of angiotensin conveing enzyme which is located on the surface of endothelial cells of the pulmonary capillary. This enzyme conves the inactive decapeptide angiotensin I into aldosterone stimulating octapeptide angiotensin II. This angiotensin II stimulates the production of aldosterone which increase sodium resoption, thereby maintaining sodium balance. Ref: Pulmonary Physiology, Lange Physiology Seires, 6th Edition, Pages 215-226.