Which statement about the renin-angiotensin system is correct?

• A. Renin raises blood pressure because of angiotensin and aldosterone secretion.
• B. Prostaglandin increases blood flow and vascular permeability.
• C. Bradykinin regulates intrarenal blood flow via vasodilation or vasoconstriction.
• D. Erythropoietin promotes calcium absorption in the gastrointestinal tract.

Answer: (A)

Renin kick-starts a cascade that raises blood pressure by generating angiotensin II, which constricts vessels, and by promoting aldosterone release, which increases sodium and water reabsorption. This combination elevates blood pressure, so describing renin as raising BP because angiotensin and aldosterone are produced captures how the system works. The other statements involve parts of unrelated pathways or effects: prostaglandins can influence renal blood flow but not through the renin-angiotensin axis; bradykinin is part of the kallikrein-kinin system and is affected by ACE, but it isn’t the primary driver of BP via renin; erythropoietin affects red blood cell production and has no role in calcium absorption in the gut.