ACE inhibitors mechanism of action?

• A. Inhibit angiotensin-converting enzyme, reducing angiotensin II and aldosterone
• B. Block angiotensin II receptor
• C. Increase renin release
• D. Inhibit aldosterone synthesis directly

Answer: (A)

Blocking the enzyme that converts angiotensin I to angiotensin II reduces angiotensin II levels. Since angiotensin II drives vasoconstriction and stimulates aldosterone release, lowering it leads to vasodilation and less aldosterone-mediated sodium and water retention, which lowers blood pressure. ACE inhibitors also prevent breakdown of bradykinin, increasing its levels and contributing to additional vasodilation (and can explain cough or angioedema). This is different from blocking the angiotensin II receptor (an ARB) or directly inhibiting aldosterone synthesis. Renin release can rise due to reduced negative feedback, but that is a secondary effect, not the primary mechanism.