A 41-year-old woman is diagnosed with severe hypertension and shows an elevated right renal vein renin activity. What is the most likely source of the vasoconstrictor contributing to her hypertension?

• A. Adrenal medullary chromaffin cells
• B. Glomerular afferent arteriole
• C. Glomerular efferent arteriole
• D. Renal juxtaglomerular cells

Answer: (D)

The most likely source of the vasoconstrictor contributing to the woman's severe hypertension is the renal juxtaglomerular cells. These specialized cells are located in the kidney, specifically at the junction of the afferent arterioles and the glomeruli. They are responsible for producing renin, an enzyme that plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance.

In the context of this patient, the elevated renin activity in the right renal vein suggests that there is a dysfunction or pathological condition in that kidney, potentially due to renal artery stenosis or another cause of ischemia. The juxtaglomerular cells respond to decreased perfusion pressure or low sodium levels by releasing renin. This renin then converts angiotensinogen from the liver into angiotensin I, which is subsequently converted into angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II is a potent vasoconstrictor that can lead to increased blood pressure by constricting blood vessels and stimulating aldosterone secretion, promoting sodium and water retention.

Thus, in this scenario, the heightened renin activity indicates that the juxtagl