Renal Ion Transport

Question 1

Renal medicine and transporters

Answer 1

Bicarbonate reabsorption in proximal tube controls pH

Na+ reuptake by kidney - blood pressure (lots = hypertension)

Question 2

Where is Na+ and bicarbonate reabsorbed? (After being removed)

Answer 2

Proximal tubule

Question 3

How is sodium reabsorbed from filtrate to proximal tubule?

Answer 3

FILTRATE —>Proximal Tubule—>Capillary

Na+K+ATPase pumps sodium out of proximal tube to capillary

Filtrate: sodium bicarbonate
Splits into sodium and bicarbonate

Na —> proximal tubule (via NHE)

Question 4

Importance of Hydrogen ions being. Pumped into filtrate

Answer 4

Buffering bicarbonate/bicarbonate is buffering them

Question 5

What then happens in the filtrate (lumen)?

Answer 5

Hydrogen and bicarbonate combine to form carbonic acid

Converted to water and CO2 via carbonic anhydrase

Question 6

What happens to the water and CO2 in lumen

Answer 6

Diffuses across to proximal tubule cell
Carbonic anhydrase then converts it back into carbonic acid
Splits off into hydrogen and bicarbonate

Hydrogen can be re used (via NHE pump)

Question 7

How does bicarbonate leave proximal tubule?

Answer 7

Bicarbonate enters capillary via anion exchange
BiCarbonate into capillary, Cl- out of capillary

(Chloride gradient is inwards so provides force)

Question 8

What occurs under normal circumstances in bicarbonate absorption?

Answer 8

All is usually reabsorbed

Used as a buffer in the body

Question 9

How is Na reuptake inhibited?

Answer 9

Amiloride (NHE inhibitor)
Loop diuretics (Na+K+2Cl- inhibitor)
Thiazides (Na+Cl- cotransporter inhibitor)
Spironolactone (mineralcorticoid antagonist)

Question 10

Purpsose of inhibiting Na reabsorption

Answer 10

Reduces water reabsorbed, reduce blood volume, reduce blood pressure

Question 11

Mechanism of amiloride

Answer 11

Inhibits NHE (sodium hydrogen exchanger) so sodium stays in lumen and filtrate is urinated out with water

Question 12

Problems with amiloride

Answer 12

Inhibits reabsoprtion of bicarbonate (need hydrogen ions from NHE)
No buffering system for body

Question 13

Other ways sodium/water reabsorption is regulated

Answer 13

Aquaporins - ADH stimulates

Aldosterone stimulates

Question 14

Treatment for aldosterone hypertension

Answer 14

Spironolactone - mineralcorticoid receptor antagronist

Blocks binding of aldosterone

Question 15

where is blood filtered in kidney?

Answer 15

Glomerelus

Question 16

Where does amiloride act?

Answer 16

NHE inhibitor
proximal tubule
Distal convoluted tubule
cortical collecting duct

Question 17

Where do loop diuretics act?

Answer 17

NKCC2 (Na+K+2Cl- cotransporter inhibitor)

Thick ascending limb

Question 18

Where do thiazides act?

Answer 18

Na+Cl- cotransporter (NCCT)

Distal convoluted tubule

Question 19

Where does spironolactone act?

Answer 19

Cortical collecting duct (mineralocorticoid antagonist)

Question 20

Where does Na+ reuptake occur?

Answer 20

Proximal tubule
Thick ascending limb
Cortical collecting duct
Distal convoluted tubule

Question 21

Order of kidney filtrate

Answer 21

Glomerulus 
Proximal tubule
Thick ascending limb
Distal convoluted tubule 
Cortical collecting duct