Renal Regulation of ECF Volume and Diuretics

Question 1

osmoreceptors are located in the

Answer 1

hypothalamus

Question 2

baroreceptors are located in the

Answer 2

afferent arteriole to provide negative feedback loops to control water balance

Question 3

renal response changes in ECF (5):

Answer 3

1. renal sympathetic nerve activity
2. renin-angiotension II
3. renin-aldosterone
4. arginine vasopressin (AVP) aka anti-diuretic hormone (ADH)
5. atrial natriuretic peptide (ANP)

Question 4

Renal Sympathetic Nerve Activity:
1. Renal sympathetic nerves

Answer 4

a. induces the release of renin –> increases Ang II –> increases TPR, [ADH], and [aldosterone]
b. increase Na reabsorption in the PT –> water reabsorption

Question 5

Renal Sympathetic Nerve Activity:
2. Renin –> Angiotension II
renin secretion regulated by:

Answer 5

1. sympathetics –> renin release
2. renal baroreceptors: afferent arteriole sense low pressure –> renin release high pressure inhibits release
3. macula dense’s osmoreceptors: reduced tubular flow activates osmoreceptors –> renin release

Question 6

Renal Sympathetic Nerve Activity:
2. Renin –> Angiotension II
effects of angiotensin II

Answer 6

a. increase TPR to increase BP
b. stimulate pos. pituitary to release ADH
c. stimulates adrenal cortex to release aldosterone
c. constriction of efferent arteriole –> increase GFR
d. stimulates Na reabsorption in PT by increasing insertion and activity of apical Na-H antiporter

Question 7

Renal Sympathetic Nerve Activity
2. Renin –> Angiotension II
effects of angiotensin II on brain and glands

Answer 7

a. increases the sensation of thirst
b. stimulates posterior pituitary to release vasopressin to increase water reabsorption
c. stimulates aldosterone synthesis and release from adrenal cortex which enhances Na reabsorption

Question 8

Renal Sympathetic Nerve Activity
3. Renin –> AngII –> Aldosterone
Aldosterone release induced by:

Answer 8

a. angiotension II
b. hyperkalemia
c. plasma acidosis

Question 9

Mechanism of Action of Aldosterone

Answer 9

a. primarily acts upon the principal cells of the distal tubule and CD
b. synthesizes apical epithelial Na channels (ENaC)
c. opens apical K+ (loss) both augment Na and water reabsorption

Question 10

Na enters principal cells via ENaC that can be blocked by the diuretic

Answer 10

amiloride

Question 11

Na reabsorption can be slowed by

Answer 11

spironolactone

Question 12

Renal Sympathetic Nerve Activity
5. Arginine Vasopressin (AVP) aka Anti-diuretic hormone (ADH)
release is stimualted by

Answer 12

a. increased osmolarity –> promotes water reabsorption
b. angiotensin II
c. baroreceptors (low pressure)

Question 13

Antidiuretic hormone MOA

Answer 13

promote insertion of aquaporin channels into collecting tubule to drive water reabsorption

Question 14

Renal Sympathetic Nerve Activity
6. Atrial Natriuretic Peptide (ANP)
Primary effects:

Answer 14

PRESSURE OVERLOAD
Hypertension can induce release of ANP from heart
a. promotes Na excretion –> water loss
b. induces systemic vasodilation
c. only released when ECF volume is really expanded
d. inhibits renin and aldosterone secretion

Question 15

Beneficial Effects of Angiotensin II Blockade

Answer 15

a. inhibiting angiotensin II via ACE inhibitors or AT1 receptor blockers) will decrease efferent arteriolar resistance decreasing glomerular capillary pressure

Question 16

ACE inhibitor or angiotensin II blocker mechanisms

Answer 16

1. reduce efferent arteriolar constriction
2. lower systemic blood pressure
3. reduce proteinuria
4. reduce production of cytokines
   3 and 4 will be on EXAM

Question 17

ACE inhibitors further increase

Answer 17

the half-life of bradykinin (vasodilator of afferent arteriole) which promotes the dilation of afferent arterioles and increases GFR and RBF

Question 18

Diabetes (high blood sugar) leads to an increase in a unique

Answer 18

Na-Glucose co-transporter (SGLT2) in the proximal tubule
- SGLT2 alters tubuloglomerular feedback leading to
a. dilation of afferent arteriole by NO
b. constriction of efferent
c. increase filtration pressure, Pgc, and GFR
d. hyper-filtration and glomerulosclerosis

Question 19

Diuretics function

Answer 19

inhibit Na reabsorption
prevents Cl- reabsorption
prevents osmotic gradient for water reabsorption

Question 20

Osmotic Diuretics MOA and location

Answer 20

1. proximal tubule
   unreabsorbable solutes such as mannitol
   they are used in cases of acute fluid overload

Question 21

Carbonic Anhydrase Inhibition MOA and location

Answer 21

1. proximal tubule
   acetazolamide is inhibitor of CA which slows the Na-H exchanger on the apical membrane
   - reduces H+ excretion resulting in metabolic acidosis

Question 22

Loop Diuretics MOA and location

Answer 22

1. TAL of loop of henle
   Furosemide (Lasix) are used to treat acute pulmonary edema and patients with congestive heart failure
   - they work by blocking Na/K/2Cl co-transporter

Question 23

Thiazide Diuretics MOA and location

Answer 23

1. distal convoluted tubule
   block the Na/Cl co-transporter
   limits Na re-absorption and promotes water excretion
   promotes Ca reabsorption
   there is still net Na and water loss
   lowers BP and treats kidney stones resulting from hypercalciuria
   help treat osteoporosis

Question 24

Amiloride Diuretic MOA and location

Answer 24

K+ sparing diuretics
1. collecting duct –> principal cells
- inhibits ENaC which prevents Na reabsorption and leads to water excretion

Question 25

Spironolactone MOA and location

Answer 25

K+ sparing diuretics
1. collecting duct –> principal cells
- block aldosterone receptors
promotes Na reabsorption and retention of water at expense of K excretion
inhibition of aldosterone leads to Na and water loss