Renin

Renin (EC 3.4.23.15) is a peptide hormone released by the kidneys in response to low blood volume, or low body NaCl content.

Renin activates the renin-angiotensin system by cleaving angiotensinogen, in the liver to produce angiotensin I, which is further converted into angiotensin II in specialized lung capillaries, which ultimately constricts blood vessels, increases ADH and aldosterone production, and stimulates the hypothalamus to activate the thirst reflex, leading to increased blood pressure.

See also: Angiotensin-converting enzyme