What is the mechanism of action of ACE inhibitors such as lisinopril?

ACE inhibitors, like lisinopril, work primarily by blocking the conversion of angiotensin I to angiotensin II. This action leads to several important physiological effects. Angiotensin II is a potent vasoconstrictor, and its production promotes increased blood pressure and stimulates aldosterone secretion, which in turn leads to sodium and water retention.

By inhibiting this conversion, ACE inhibitors effectively lower levels of angiotensin II, resulting in vasodilation, reduced blood pressure, decreased workload on the heart, and lower fluid retention. This mechanism is particularly beneficial in treating conditions such as hypertension and heart failure.

The other mechanisms mentioned in the choices fall outside the action of ACE inhibitors. For instance, serotonin synthesis inhibition pertains to medications like SSRIs or other antidepressants, calcium influx blockade is characteristic of calcium channel blockers, and cyclooxygenase inhibition relates to nonsteroidal anti-inflammatory drugs (NSAIDs). Thus, the primary role of ACE inhibitors in modulating the renin-angiotensin-aldosterone system clearly aligns with the mechanism of action that involves blocking the conversion of angiotensin I to angiotensin II.