Renal Regulation

Question 1

What is the juxtaglomerular apparatus composed of?

Answer 1

Mesangial Cells
JG cells - modified smooth muscle cells of afferent arteriole
Macula densa - Na/Cl sensor, part of the DCT

Question 2

What do JG cells do?

Answer 2

Secrete renin in response to decrease in blood pressure, or increase in sympathetic tone (via B1 receptors).

Question 3

What do macula densa cells do?

Answer 3

In response to low Na/Cl delivery to DCT they:

1. Release adenosine leading to vasoconstriction
2. Secrete prostaglandins that induce JG cells to secrete renin

Question 4

What does renin release cause?

Answer 4

Conversion of angiotensinogen to angiotensin I

Question 5

What happens to angiotensin I?

Answer 5

It is converted to angiotension II by ACE (angiotension converting enzyme).

Question 6

What else does ACE do?

Answer 6

Degrades bradykinin. Bradykinin is vasodilatory.

Question 7

What does angiotensin II do at the adrenal glands?

Answer 7

Stimulates synthesis of aldosterone via stimulating aldosterone synthase. (Increase Na+ and H20 reabsorption, K+ excretion).

Question 8

What does angiotensin II do at the posterior pituitary?

Answer 8

Stimulates ADH release. (Increase H2O absorption)

Question 9

What does angiotensin II do at the hypothalamus?

Answer 9

Stimulates thirst

Question 10

What does angiotensin II do at the vascular smooth muscle? What receptor?

Answer 10

AT1 receptor (angiotensin II receptor Type 1), constricts vascular smooth muscle –> increases BP

Question 11

What does angiotension II do at the level of the kidneys?

Answer 11

1. Constricts efferent arteriole of the glomerulus (increases FF and GFR)
2. Increases PCT Na+/H+ activity - Na+, H2O and bicarb rebsorption

Question 12

Summary: Where all does angiotensin II have action?

Answer 12

Hypothalamus (thirst), posterior pituitary (ADH), vascular smooth muscle (vasoconstrict), adrenal glands (aldosterone), efferent arteriole (constrict), PCT (increase Na/H+ channel)

Question 13

Why isn’t there reflex bradycardia with AT II’s pressor effects?

Answer 13

It also affects baroreceptor function.

Question 14

What does ANP/BNP do?

Answer 14

Release from atria/vent in response to increased volume, acts as a check on RAAS system.

1. Relaxes vascular smooth muscle via cGMP, afferent arteriole preferentially -> leads to increase in GFR, decrease in renin
2. Also blocks ENaC in principal cell, thus promoting natriuesis/diuresis.

Question 15

What does ADH regulate primarily?

Answer 15

Osmolarity, responds to low blood volume states.

Question 16

What does aldosterone primarily regulate?

Answer 16

ECF volume and Na+ content; responds to low blood volume states.

Question 17

What is the role of prostaglandins in the kidney?

Answer 17

Paracrine secretion vasodilates the afferent arterioles to increase RBF

Question 18

What is the effect of NSAIDs on the kidney?

Answer 18

Constricts the afferent arteriole, decreases GFR, may lead to acute renal failure