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ESA3 - Urinary System > Diuretics > Flashcards

Diuretics Flashcards

1
Q

What is diuresis?

A

Increased formation of urine by the kidney

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2
Q

How do diuretics generally act?

A

By blocking reabsorption of sodium and water by the tubule, blocking the action of aldosterone, modifying filtrate content or inhibiting the activity of carbonic anhydrase

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3
Q

What channel pumps Na+ out across the basolateral membrane of the tubule?

A

Na-K-ATPase

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4
Q

True or False:

Na+ moves across the apical membrane of tubules against its concentration gradient

A

False

Moves down its concentration gradient - set up by Na/K pump on basolateral membrane that pumps sodium out of the cell - therefore tubular cell concentration of sodium is low

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5
Q

True or False:

The Na/K pump on the basolateral membrane is common to all segments of the tubule

A

True

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6
Q

What sodium channels are present in the apical membrane of the proximal tubule?

A

Na-H antiporter
Na-Glucose
Na-AA etc

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7
Q

What sodium channels are present in the apical membrane of the loop of henle?

A

NKCC (Na K 2 Cl)

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8
Q

What sodium channels are present in the apical membrane of the early distal tubule?

A

NaCl symporter

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9
Q

What sodium channels are present in the apical membrane of the late distal tubule and collecting duct?

A

ENaC

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10
Q

What do diuretics reducing ENaC activity also reduce?

A

K+ secretion

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11
Q

In which part of the kidney is there a net secretion of K+?

A

Principal cells in late DT and CD

K+ brought into cell on the basolateral membrane via Na/K pump and leaves via a K+ channel on the apical membrane

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12
Q

Does Na+ absorption favour K+ excretion in the principal cells?

A

Yes

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13
Q

Where do loop diuretics act?

A

Loop of henle

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14
Q

What do loop diuretics block?

A

NaKCC

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15
Q

Where do thiazide diuretics act?

A

Early DT

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16
Q

What do thiazide diuretics block?

A

Na-Cl cotransporter

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17
Q

What do K+ sparing diuretics act on?

A

Late DT and CD

Block ENaC

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18
Q

How does aldosterone act on principal cells of the late DT and CD?

A

Increases Na+ reabsorption via ENaC

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19
Q

How do aldosterone antagonists decrease Na reabsorption?

A

Competitive inhibition of aldosterone receptor - so aldosterone cannot increase reabsorption

20
Q

How do osmotic diuretics work?

A

Increase osmolarity of filtrate - reduce water and Na+ reabsorption throughout the tubule

21
Q

What are some examples of loop diuretics?

A

Furosemide, bumetanide

22
Q

What is used in acute pulmonary oedema?

A

IV Furosemide (loop diuretic)

23
Q

Why are loop diuretics used in heart failure?

A

For treatment of symptoms (breathlessness, oedema)

  • Diuretic effect
  • Vaso and venodilation
24
Q

When are loop diuretics used to treat fluid retention and oedema?

A

In nephrotic syndrome, renal failure, cirrhosis of liveer

25
Q

Why are loop diuretics useful in treatment of hypercalcaemia?

A

Impairs calcium absorption in loop of henle, increases urinary excretion of calcium

26
Q

What effect does thiazide diuretics have calcium absorption?

A

Increases Ca2+ absorption - reduces Ca2+ loss in urine

27
Q

What is an example of a thiazide diuretic?

A

Bendroflumethiazide

28
Q

True or False:

Aldosterone antagonists are shown to reduce mortality in HF

A

True

Used in lon term tretment of HF (non diuretic effect)

29
Q

What is the preferred drug for ascites and oedema in cirrhosis?

A

Aldosterone antagonists (eg spironolactone)

30
Q

What is used to treat hypertension due to primary hyperaldosteronism (Conns syndrome)?

A

Aldosterone antagonist - spironolactone

Adrenal hyperplasia/tumour -> causes increased secretion of aldosterone -> hypertension

31
Q

What does amiloride block?

A

ENaC

32
Q

Why are ENaC blockers usually used in combination with loop or thiazide diuretics?

A

ENaC blockers have a K+ sparing effect

Used to minimise K+ loss

33
Q

What does the rate of K+ secretion in the DT and CD depend on?

A

Concentration gradien across apical membrane and rate of sodium abdorption (inward movement of Na+ creates a favourable lumen negative potential for K+ secretion)

34
Q

How can loop and thiazide diuretics lead to hypokalaemia?

A

Block Na+ reabsorption in LoH or early DT

Increased Na absorption by principal cells

Favourable electrical gradient for K+ excretion

More K+ loss in urine leading to hypokalaemia

35
Q

Which diuretics are K+ sparing?

A

ENaC blockers and aldoserone antagonists

36
Q

Why should spironolactone not be used along with K+ supplements?

A

Increased risk of hyperkalaemia as spironalactone is an aldosterone antagonist which is K+ sparing

37
Q

How can glomerular disease lead to oedema?

A

Increase in GBM permeability to protein - proteins filtered and lost in urine

Causes low plasma albumin, resulting in a low plasma oncotic pressure -> peripheral oedema

Reduced circulatory volume -> RAAS activates

38
Q

What conditions are diuretics used in?

A

Conditions with ECF expansion and oedema

(Congestive HF, nephrotic syndrome, cirrhosis, kidney failure)

Acute pulmonary oedema

HF

Hypertension

39
Q

What are some adverse effects of diuretics?

A 
Potassium abnormalities
Hypovolaemia
Hyponatraemia
Increased uric acid levels -> gout attacks
Erectile dysfunction (thiazides)
Gynaecomastia (spironolactone)
40
Q

What is an example of a carbonic anhydrase inhibitor?

A

Acetazolamide

41
Q

Where do carbonic anhydrase inhibitors act?

A

Proximal tubule - inhibits action of carbonic anhydrase in brush border + PCT cell

42
Q

What is an example of an osmotic diuretic?

A

Mannitol

43
Q

What is IV mannitol used to treat?

A

Cerebral oedema

44
Q

What are some diseases that cause diuresis?

A

Diabetes mellitus
Diabetes insipidus
Psychogenic polydipsia

45
Q

What are the two types of diabetes insipidus?

A

Cranial - decreased ADH release from post pituitary

Nephrogenic - poor response of CD to ADH

ESA3 - Urinary System (16 decks)

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