Renin

Renin is an enzyme produced by the kidneys that plays a crucial role in regulating blood pressure and fluid balance. When blood pressure drops or there's a decrease in sodium levels, the kidneys release renin. Renin then initiates a series of reactions, leading to the production of a hormone called angiotensin II, which constricts blood vessels and signals the kidneys to retain sodium and water. These actions increase blood pressure and restore fluid balance, helping the body maintain stable blood pressure levels.