The first step leading to angiotensin II production is the secretion of what by the kidneys? Multiple Choice Calcitriol Angiotensin converting enzyme Angiotensin I Angiotensinogen Renin

The correct answer is "Renin".

Explanation:

The secretion of the enzyme renin by the kidney is one mechanism used by the kidneys for blood pressure regulation. The secretion of renin is the first step leading to angiotensin II production, in what is known as the renin-angiotensin system (RAS). Renin catalyzes the conversion of angiotensinogen to angiotensin I, which is subsequently converted to angiotensin II by the angiotensin-converting enzyme (ACE).