Renal Tubular Disoders

Question 1

What is the role of the proximal tubules

Answer 1

Active reabsorption of multiple solutes

Question 2

What generates the sodium gradient in proximal tubules

Answer 2

Na/K ATPases

Question 3

What organelle is plentiful in the PCT and why

Answer 3

Mitochondria as proximal tubules are metabolically active cells

Question 4

What condition is related to failure of glucose reabsorption

Answer 4

Renal glycosuria

Question 5

Describe bicarbonate reabsorption

Answer 5

In the tubular lumen, HCO3- and H+ will combine under the influence of carbonic anhydrase to form CO2 and H2O

H2O + CO2 can be passively reabsorbed into proximal tubular cells where they combine to form carbonic acid

Carbonic anhydrase within the tubular cells breaks down this acid to reform H+ and HCO3-

Anti porter returns H+ to the tubular lumen and reabsorbs Na into the cells which is then actively reabsorbed into the bloodstream

HCO3- also gets reabsorbed into the bloodstream

Question 6

What condition is caused be a failure of bicarbonate reabsorption

Answer 6

Proximal renal tubular acidosis

Question 7

Function of the loop of henle

Answer 7

Generates medullary [gradient]

Active Na reabsorption in thick ascending limb

Question 8

What is the role of the NKCC2 transporter in the thick ascending limb

Answer 8

Pulls in a Na+, 2x Cl- and a K+ from the tubular lumen into the cell

Question 9

K+ is recycled into the tubular lumen if the TAL by which transporter

Answer 9

ROMK

Question 10

How is a negative electrochemical gradient generated in the interstitial fluid of the TAL

Answer 10

1 Na is reabsorbed for every 2 Cl- so the overall charge is negative

Question 11

This electrochemical gradient in the interstitial fluid drives paracellular transmission of which 2 ions

Answer 11

Calcium

Magnesium

Question 12

What is the defect in barrters syndrome

Answer 12

NKCC2, ROMK, CLCKa/b

Question 13

What transporters reabsorb Cl- from the cell into interstitial fluid

Answer 13

ClCKa/b which both have a subunit called barrtin

Question 14

Function of the DCT

Answer 14

fine tuning of Na reabsorption and K+ and acid base balance

Question 15

Function of collecting duct

Answer 15

Mediates water reabsorption and [urine]

Question 16

What is aldosterone

Answer 16

Steroid hormone that acts on DCT and collecting duct

Predominately acts on transcription increasing the expression of several transporters

Question 17

What transporter enables Na transport into principal cells

Answer 17

Epithelium sodium channels

ENaC

Question 18

What’s the role of the Na/K ATPase in the aldosterone mechanism

Answer 18

Pumps 3Na+ from the principal cells into the blood
Pumps 2K+ from the blood inti the principal cells
This generates an electrochemical gradient

Question 19

What does the electrochemical gradient across the principal cells drive

Answer 19

H2O + CO2 dissociates to H+ and HCO3- in the presence of carbonic anhydrase
Antiporter transports H+ into the the lumen and K+ into the cell
HCO3- is reabsorbed into the blood with K+