RRAS Axis

Question 1

Where do the juxtaglomerular cells in the wall of the afferent arteriole secrete renin?

Answer 1

into the lumen of the afferent arteriole and the renal lymph

Question 2

What factors promote renin secretion?

Answer 2

• Stretch receptors in the afferent arteriole sense decreased stretch (hypotension),
• the sympathetic nerves ending in the juxtaglomerular cells, and
• decreases NaCl delivery to the macula densa

Question 3

What is the major determinant of renin release?

Answer 3

In normal subjects, the major determinant of renin secretion is Na+ intake: a high intake expands the extracellular volume and decreases renin release whereas a low intake (or fluid loss from any site) leads to a reduction in extracellular volume and stimulation of renin secretion.

Question 4

What does renin do?

Answer 4

works to activate angio II and aldosterone

Question 5

The effects of angiotensin II are mediated by binding to specific angiotensin II receptors, namely:

Answer 5

AT1 and AT2.

Question 6

What does binding of angio II to AT1 promote? AT2?

Answer 6

The vascular and renal tubular actions are primarily mediated by the AT1 receptors.

The effects of the AT2 receptors are less well understood.

Question 7

Angiotensin II promotes renal NaCl reabsorption and therefore expansion of the plasma volume. How?

Answer 7

This occurs by at least two mechanisms: direct stimulation of Na+ reabsorption in the early proximal tubule via the NHE pump and by increased secretion of aldosterone from the adrenal cortex, which enhances Na+ transport in the cortical collecting tubule.