Diuretics

Question 1

What do diuretics do?

Answer 1

Inhibits Na+ reabsorption, which increases Na+ excretion from the body, taking water with it (and reducing ECF volume)

Question 2

What are diuretics usually used for?

Answer 2

Used to treat edema or hypertension

Question 3

What is the most common primary cause of hypertension?

Answer 3

Increase in effective circulating volume

Question 4

What is the mechanism of acetazolemide (a diuretic)?

Answer 4

It inhibits the enzyme carbonic anhydrase. This enzyme is important in the Na/HCO3 transport of the proximal tubule.

Question 5

What is the mechanism of hydrochlorothiazide (a diuretic)?

Answer 5

It inhibits the cotransport of Na+/Cl- in the distal convoluted tubule.

Question 6

What is the mechanism of spironolactone (a diuretic)?

Answer 6

Because it’s chemical structure is very similar to aldosterone, it competitively inhibits aldosterone receptors in the initial collecting tubule and the cortical collecting tubule.

Question 7

What is a side effect of diuretics?

Answer 7

They interfere with the reabsorption of other essential solutes, which disrupts the balance between the different solutes.

Question 8

Diuretics usually inhibit channels on the apical or basolateral side of the tubule cells?

Answer 8

Apical.

Question 9

Why might the concentration of the diuretic drug be low in the blood?

Answer 9

Because many plasma proteins can bind to the diuretic

Question 10

Which part of the nephron can secrete a diuretic from the blood?

Answer 10

S3 segment of the proximal tubule

Question 11

The basolateral organic anion transporter system that carries PAH can also secrete which diuretics into the tubule lumen if they are present in the blood? (3)

Answer 11

1. Furosemide
2. Ethacrynic acid
3. Spironolactone

Question 12

What diuretics can the organic cation transporter secrete from the blood into the tubule lumen?

Answer 12

Amiloride

Question 13

Can renal disease hinder the delivery of diuretic drugs to the tubule lumen?

Answer 13

Yep!

Question 14

Which tubule reabsorbs the largest amount of Na+?

Answer 14

Proximal tubule

Question 15

Why do diuretics that act on the proximal tubule considered weak?

Answer 15

Because Na+ re-absorption can reoccur at downstream areas of the nephron.

Question 16

What is one proximal tubule-acting diuretic?

Answer 16

Acetazolemide

Question 17

What class of diuretics are the most effective/potent?

Answer 17

Loop diuretics, because they act on downstream tubules where secondary re-absorption of Na+ occurs

Question 18

What is the site of loop diuretics?

Answer 18

TAL (thick ascending loop of Henle)

Question 19

How much Na+ is the TAL (thick ascending loop of Henle responsible for re-absorbing?

Answer 19

15% to 25%

Question 20

What are the other benefits of loop diuretics? (2)

Answer 20

1. They are long-lasting

2. They are K+-sparing

Question 21

Can you use two different classes of diuretics at the same time?

Answer 21

Yes, in fact, it produces a synergistic effect. But usually only done if the loop diuretic is not as effective as usual.

Question 22

The prolonged administration of a diuretic can lead to?

Answer 22

1. Loss of body weight

2. Transient natriuresis

Question 23

When diuretics are given, the effective circulation volume decreases. How does the body compensate for this, causing a decrease in diuretic efficacy?

Answer 23

1. Increase sympathetic outflow to the kidney
2. Increased aldosterone
3. Increased AVP
4. Hypertrophy downstream from the site of action