Cardiac Vascular Nursing Certification Practice Exam 2025 - Free Cardiac Vascular Nursing Practice Questions and Study Guide

Renin is an enzyme secreted by the kidneys that plays a crucial role in the renin-angiotensin-aldosterone system, which regulates blood pressure and fluid balance. When blood pressure drops or when there is decreased blood flow to the kidneys, renin is released into the bloodstream. This enzyme catalyzes the conversion of angiotensinogen, a precursor protein produced by the liver, into angiotensin I.

Angiotensin I itself is inactive but is further converted into angiotensin II by the enzyme angiotensin-converting enzyme (ACE). Angiotensin II is a potent vasoconstrictor that raises blood pressure and stimulates the release of aldosterone from the adrenal cortex, which promotes sodium and water reabsorption in the kidneys.

The other choices presented are not involved in the initial conversion of angiotensinogen. ACE is responsible for converting angiotensin I to angiotensin II. Antidiuretic hormone (ADH) is involved in regulating water balance, not in the initial conversion of angiotensinogen, while aldosterone is a hormone that affects sodium and water retention but does not have a role in the conversion of angiotensinogen. Therefore, renin is the correct answer as