Diuretics

Question 1

What molecules act in the nephron? (6)

Answer 1

Carbonic anhydrase inhibitor
Osmotic diuretics
Loop diuretics
Thiazides
Aldosterone antagonists
Osmotic diuretics

Question 2

Where do each molecules occur in the nephron?

a) Carbonic anhydrase inhibitor
b) Osmotic diuretics
c) Loop diuretics
d) Thiazides
e) Aldosterone antagonists
f) Osmotic diuretics

Answer 2

Carbonic anhydrase inhibitor - PCT
Osmotic diuretics - PCT
Loop diuretics - Thick ascending limb
Thiazides - DCT
Aldosterone antagonists - DCT
Osmotic diuretics - collecting duct

Question 3

What are the roles of diuretics? (3)

Answer 3

1. Interfere with ionic transport in the nephron - decrease tubular reabsorption
2. Act at different sites of the nephron: natriuresis (increase in Na+ excretion) - leads to diuresis (increase urine vol.)
3. Clinically useful in the treatment of hypertension associated with congestive heart failure - reduce blood pressure and oedema

Question 4

What is the role of osmotic diuretics?

Answer 4

Alter the osmolality of the plasma due to lack of absorption and metabolism

Question 5

How do osmotic diuretics work? (3)

Answer 5

• Freely filtered through the glomerulus and act in PCT
• Water follows the conc gradient
• Results in increased urinary output via osmosis

Question 6

What is mannitol?

Answer 6

Osmotic diuretic - increases osmolality of tubular fluid

Question 7

What are the uses of mannitol? (3)

Answer 7

• Reduce intracranial pressure
• Reduce intraocular pressure
• Maintain urine flow

Question 8

What medical use is mannitol used for?

Answer 8

Head injuries - reduce volume and pressure of fluid within the brain

Question 9

What is the role of carbonic anhydrase in proximal tubules?

Answer 9

Facilitates the exchange of H+, Na+ and H2O in the proximal tubules

Question 10

What do carbonic anhydrase inhibitors do?

Answer 10

Block this exchange of ions - reduce H+ conc. in the renal tubules

Question 11

What are carbonic anhydrase inhibitors used to treat? (4)

Answer 11

Glaucoma
Oedema
Epilepsy
High altitude sickness

Question 12

What is an example of a carbonic anhydrase inhibitor and what does it do?

Answer 12

Acetazolamide

Inhibit reabsorption of bicarbonate

Question 13

What is a loop diuretic and where does it act?

Answer 13

Prevents creation of a hypertonic interstitial in the medulla
Acts on the ascending limb of the loop of Henle

Question 14

What does a loop diuretic treat?

Answer 14

Pulmonary oedema

Question 15

What is an example of a loop diuretic and what does it do?

Answer 15

Furosemide

Blocks ion symporters in ascending limb

Question 16

What is a thiazide, where does it act and what does it do?

Answer 16

Blocks Na+ and Cl- reabsorption
Distal convoluted tubule
Increase solute in tubular fluid to decrease H2O gradient

Question 17

What is an example of thiazides and what does it do?

Answer 17

Bendroflumethiazide

Inhibits Na+ reabsorption on DCT

Question 18

What is a K+ sparing diuretic and what does it do?

Answer 18

Blocks actions of aldosterone and blocks Na+ channels

Helps maintain K+ conc in body

Question 19

What does thiazides treat?

Answer 19

Moderate heart failure

Question 20

What do K+ sparing diuretics (aldosterone antagonists) treat? (2)

Answer 20

Hypertension

Heart failure