A 44-year-old man comes to the office for a routine check-up. Past medical history is significant for hypercholesterolemia, which he has controlled through diet. His father died of a myocardial infarction at age 56, and his mother, who is still living, has a history of stroke. On physical examination, the patient's blood pressure is 160/100 mm Hg and heart rate is 70/min. He is started on enalapril. During the first 7 days of therapy, the patient's glomerular filtration rate (GFR) adjusts as shown in the graph below. Which of the following structures was most likely affected by a downstream effect of enalapril and is therefore responsible for this patient's renal response?

Question

A 44-year-old man comes to the office for a routine check-up.  Past medical history is significant for hypercholesterolemia, which he has controlled through diet.  His father died of a myocardial infarction at age 56, and his mother, who is still living, has a history of stroke.  On physical examination, the patient's blood pressure is 160/100 mm Hg and heart rate is 70/min.  He is started on enalapril.  During the first 7 days of therapy, the patient's glomerular filtration rate (GFR) adjusts as shown in the graph below.  Which of the following structures was most likely affected by a downstream effect of enalapril and is therefore responsible for this patient's renal response?

Quizplus · Accepted Answer

Enalapril is an angiotensin-converting-enzyme (ACE) inhibitor. All ACE inhibitors decrease circulating levels of angiotensin II, a substance that causes the following: As a result, reduced angiotensin II production in patients taking an ACE inhibitor would be expected to acutely decrease efferent arteriolar resistance and systemic vascular resistance. Selective efferent arteriolar dilation combined with the decreased renal perfusion pressure causes a reduction in glomerular filtration rate. Educational objective: In the kidney, angiotensin II preferentially constricts the efferent arteriole, thereby maintaining the glomerular filtration rate (GFR) within normal range. ACE-inhibitors promote efferent arteriolar dilation, causing GFR reduction.

A 44-Year-Old Man Comes to the Office for a Routine