Renin, also known as angiotensinogenase is an enzyme that participates in the body's renin-angiotensin system (RAS) that mediates extracellular volume (for example that of the blood plasma, lymph and interstitial fluid), and arterial vasoconstriction. Thus it regulates the body's mean arterial blood pressure. Discovery Renin was discovered, characterized and named in 1898 by Robert Tigerstedt, Professor of Physiology at the Karolinska Institute in Stockholm. Citation - Tigerstedt R, Bergman PG.… (More on Renin)