Which diuretic acts on the proximal tubule to inhibit water reabsorption?
Increases osmolarity of filtrate, so less water enters interstitium by osmosis
How is mannitol administered?
How does mannitol enter the filtrate?
Filtered by glomeruli
How does mannitol decrease
b) sodium reabsorption?
a) Increases omsolarity of filtrate, so less water wants to pass into the interstitium of the proximal tubules
b) Filtrate is more dilute because there's more water, so Na+ reabsorption decreases
What is mannitol used to treat?
Increased intracranial pressure (cerebral oedema, papilloedema)
Increased intraocular pressure (glaucoma)
What are two side effects of mannitol?
Hyponatraemia (inc. blood volume, so diluted)
What complication of diabetes causes osmotic diuresis?
All the SGLT2 channels are saturated
So less Na+ reabsorbed
So less H2O reabsorbed
What is an example of a carbonic anhydrase inhibitor?
What is a renal effect of carbonic anhydrase inhibitors?
Stop carbonic anhydrase from converting H+ and HCO3- to carbonic acid
So BICARBONATE is excreted
Causing metabolic acidosis
Which eye condition is carbonic anhydrase inhibitors used to treat?
Inhibits secretion of aqueous humour, reducing intraocular pressure
Where is aldosterone secreted from?
What does it do?
Increases Na+ reabsorption and K+ secretion from the distal tubules and collecting ducts
Where is ADH secreted from?
What does it do?
Posterior pituitary gland
Increases water reabsorption from collecting ducts
Which receptor does ADH bind to?
What is the problem in
a) Lack of ADH secretion from posterior pituitary
b) Resistance of V2 receptors to ADH
What causes nephrogenic diabetes insipidus?
Resistance of V2 receptor to ADH binding
Which gene mutates to cause nephrogenic diabetes insipidus?
How is neurogenic diabetes insipidus treated?
Why does ethanol cause increased diuresis?
Alcohol inhibits ADH
Why does smoking cause reduced diuresis?
Nicotine stimulates ADH
What type of receptor is V2?
G-protein coupled receptor
activates adenyl cyclase, then cAMP etc.
What change in the apical membrane does activation of V2 receptors cause?
Increased expression of aquaporins
Which drugs block V2 receptors?
How do they affect
a) water reabsorption
b) Na+ reabsorption?
Block V2 receptors, so less water is reabsorbed
Same amount of Na+ is reabsorbed, but smaller BV, so HYPERNATRAEMIA
What is an example of a vaptan which is used to treat SIADH and ADPKD?
Which transporters are found in the proximal tubules and can be targeted by -flozins?
Which sodium-glucose transporters are found in the
a) early proximal
b) late proximal
How does SGLT work?
Transports glucose INTO cells, against a concentration gradient, by coupling it to Na+ transport down a concentration gradient
Which SGLT channels have
a) a low affinity and high capacity
b) a high affinity and low capacity?
Why is this useful?
a) SGLT2 (proximal)
b) SGLT1 (distal)
If SGLT2 is overloaded with glucose, SGLT1 picks up the rest
What renal symptom do SGLT2 inhibitors cause?
Which drugs are used to inhibit SGLT2 inhibitors in the treatment of diabetes?
What are the effects on SGLT2 inhibitors?