Plasma renin activity measurements are usually made by measuring which of the following using immunoassay?

Plasma renin activity measurements are usually made by measuring which of the following using immunoassay?

• A. Angiotensinogen
• B. Angiotensin I
• C. Angiotensin II
• D. Angiotensin-converting enzyme

Answer: (B)

The main idea is that plasma renin activity is assessed by how much angiotensin I is produced when renin acts on its substrate, angiotensinogen. In the typical immunoassay PRA setup, plasma is incubated with excess angiotensinogen and the generated angiotensin I is measured. Because Angiotensin I is the direct product of renin’s action, its amount directly mirrors renin activity. Angiotensinogen is simply the substrate, not the readout; Angiotensin II is downstream and influenced by ACE and other steps, so it wouldn’t specifically reflect renin activity.

The main idea is that plasma renin activity is assessed by how much angiotensin I is produced when renin acts on its substrate, angiotensinogen. In the typical immunoassay PRA setup, plasma is incubated with excess angiotensinogen and the generated angiotensin I is measured. Because Angiotensin I is the direct product of renin’s action, its amount directly mirrors renin activity. Angiotensinogen is simply the substrate, not the readout; Angiotensin II is downstream and influenced by ACE and other steps, so it wouldn’t specifically reflect renin activity.