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The Renal System > Drugs Acting on the Kidney 2 > Flashcards

Drugs Acting on the Kidney 2 Flashcards

1
Q

Give an example of an osmotic diuretic

A

Mannitol

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2
Q

Which properties of osmotic diuretics allow them to initiate a diuresis?

A

Small molecular size - Easily filtered

Not reabsorbed - Increase filtrate osmolarity

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3
Q

How do osmotic diuretics affect electrolyte reabsorption?

A

Decrease it

(filtrate is more diluted)

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4
Q

What are the side effects of osmotic diuretics?

A

Transient expansion of blood volume

Hyponatraemia

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5
Q

Why are carbonic anhydrase inhibitors redundant as diuretics?

A

Weak and self limiting effect

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6
Q

Why do carbonic anhydrase inhibitors cause a metabolic acidosis?

A

The is an increase in the excretion of bicarbonate (along with sodium, potassium and water)

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7
Q

What is the main direct action of vasopressin?

A

Insertion of aquaporins into the apical membrane of the collecting tubule

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8
Q

What are the two type of diabetes insipidus?

A

Neurogenic

Nephrogenic

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9
Q

What causes neurogenic diabetes insipidus?

A

Lack of vasopressin excretion from the posterior pituitary

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10
Q

How can neurogenic DI be treated?

A

Demopressin (synthetic vasopressin with only V2 selectivity)

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11
Q

What does activation of the V1 vasopressin receptor do?

A

Vasoconstriction of circulation and in the kidneys

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12
Q

What does activation of the V2 vasopressin receptor do?

A

Insertion of aquaporins into the apical membrane of the collecting duct cells

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13
Q

How do the following substances affect vasopressin?

a) Ethanol
b) Nicotine

A

a) Ethanol - Inhibits (so more water is lost)
b) Nicotine - Enhances (so less water is lost)

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14
Q

What causes nephrogenic DI?

A

Usually recessive and X-linked mutations in V2 receptor gene (AVPR2)

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15
Q

Why are the Vaptans called “aquaretics”?

A

They do not cause loss of electrolytes - only water

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16
Q

How do the Vaptans function?

A

Competitive antagonists of all/some vasopressin receptors

By blocking V1, vasoconstriction occurs

By blocking V2 aquaporin 2 channels are not recruited into the apical membrane

17
Q

Give an example of a Vaptan

A

Tolvaptan

18
Q

Where does the reabsorption of glucose take place in the kidneys?

A

Proximal tubule

19
Q

Which receptors are responsible for glucose reabsorption?

A

SGLT2

SGLT1

20
Q

At which blood glucose level will glucose begin appearing in the urine and what is the cause of this?

A

>11mmol/l

Reabsorptive mechanisms are overloaded

21
Q

Under normal conditions, what percentage of glucos eis each of the following channel types responsible for reabsorbing?

A

SGLT2 - 90% (occurs first in the tubule)

SGLT1 - 10% (occurs second when most of the work is done)

22
Q

How do both SGLT channels transport glucose into the luminal cells?

A

Coupled with sodium against a concentration gradient

23
Q

For which reason can sodium be continually pumped into the luminal cells with glucose?

A

Na+/K+ATPase on the basolateral membrane pumps sodium out of the cell maintain a sodium gradient into the cell at the apical membrane

24
Q

How do the two SGLT transporters differ in stoichiometry and also affinity for glucose?

A

SGLT2 - 1:1 (Na:glucose), high absorptive capacity and low affinity for glucose

SGLT1 - 2:1 (Na:glucose), low absorptive capacity and high affinity for glucose

25
Q

What is Familial Renal Glucosuria?

A

A familial condition in which there is an inherited mutation in the SGLT2 gene resulting in a dysfunctional protein

Patients usually have no symptoms, yet a persistant glucosuria

26
Q

Which SGLT receptor is targeted for therapeutic blockade and why?

A

SGLT2

It is responsible for reabsorbing more glucose so its blockade results in higher glucose loss

27
Q

Give examples of SGLT2 inhibitors

A

Empagliflozin

Dapagliflozin

28
Q

How are prostaglandins formed?

A

From arachidonic acid by cyclo-oxygenase enzymes (COX1 and 2)

29
Q

What are the major prostaglandins synthesised in the kidney?

A

PGE2 - medullary formation

PGI2 (prostacylin) - glomerular formation

30
Q

What do prostaglandins do?

A

Vasodilators

Natriuretic (causes sodium excretion at kidneys)

Synthesised in response to ischaemia

Upregulate angiotensin II, ADH and bradykinin

31
Q

How do prostaglandins inpact GFR?

A

Direct vasodilator effect on afferent arteriole

Releasing renin and indirectly increasing angiotensin II which vasoconstricts the efferent arteriole

Both factors increase filtration pressure

32
Q

Why should NSAIDs be avoided in renal failure?

A

They inhibit COX activity and lower prostaglandin concentration

This lowers GFR due to lack of prostaglandins

33
Q

What is the action of allopurinol?

A

Inhibition of urate synthesis

The Renal System (37 decks)

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