<prompt> Action of renin: March 2013ErythropoiesisContols secretion of melatoninConves angiotensinogen to angiotensin IConves angiotensinogen Ito angiotensinogen II  <response>: Ans. C i.e. Conves angiotensiogenogen to angiotensin I ReninAngiotensinogenase It is an enzyme that paicipates in the bodys renin-angiotensin system RAS -- also known as the renin-angiotensinaldosterone axis--that mediates extracellular volume i.e., that of the blood plasma, lymph and interstitial fluid, and aerial vasoconstriction. Thus, it regulates the bodys mean aerial blood pressure. The renin enzyme circulates in the blood stream and breaks down hydrolyzes angiotensinogen secreted from the liver into the peptideangiotensin I. Angiotensin I is fuher cleaved in the lungs by endothelial-bound angiotensin-conveing enzyme ACE into angiotensin II, the most vasoactive peptide. 