37kDa (340 amino acids)
Renin, also known as angiotensinogenase is an aspartic protease enzyme which cleaves angiotensinogen and yields the decapeptide angiotensin I. Pro-renin has also a receptor so it may be considered a hormone too. Renin is secreted by the juxtaglomerular cells, a specialized smooth muscle cell located in the wall the afferent arterioles.
3 stimuli promote its secretion:
- Decreased blood pressure sensed by the walls of the afferent arterioles
- Decreased sodium chloride load at the level of the macula densa
- Sympathetic nervous system activity through β1 adrenergic receptors