A 36-year-old male presents with low renin essential hypertension. Renin release from the juxtaglomerular apparatus is normally inhibited by which of the following?
A. ProstaglandinsB. Aldosterone
C. Stimulation of the macula densa
D. Increased pressure within the afferent arterioles
Answer. D. Increased pressure within the afferent arterioles
• Juxtaglomerular (JG) cells are
sensitive to changes in afferent arterial intraluminal pressure.
• Increased pressure within the
afferent arteriole leads to a decrease in renin release, whereas decreased
pressure tends to increase renin release.
• Angiotensin appears to inhibit
renin release by initiating the flow of calcium into the JG cells.
• Renin release is increased in
response to increased activity in the sympathetic neurons innervating the
kidney.
Prostaglandins, particularly PGI2
and PGE2, stimulate renin release.
• Stimulation of the macula
densa leads to an increase in renin release, and although the mechanism is not
fully understood, it appears that increased delivery of NaCl to the distal
nephron is responsible for stimulating the macula densa. Aldosterone does not appear to have any direct
effect on renin release.
