Renin is a proteolytic enzyme that is synthesised and stored by specialised cells in the wall of the afferent arteriole that is situated in the glomerulus of the kidney. These cells are anatomically and functionally associated with the cells in the wall of the distal convoluted tubules, which form the macula densa, and the whole structure is known as the juxtaglomerular apparatus.
Renin is produced in both an active and inactive form. Various in vitro techniques have been used to activate the inactive enzyme, including treatment with trypsin, pepsin, or acid, or incubation at -4¡C. The enzyme responsible for in vivo activation of renin is probably a serine protease, possibly kallikrein.
