Proximal Tubule--Muster

Question 1

Filtrate throughout proximal tubule is 300 mOsm, the same as in the interstitial/pericapilar space.

This means that reabsorption in in the proximal tubule is __________

Answer 1

isomotic

Question 2

This ion functions to move most other ions in the proximal tubule

Answer 2

Na⁺

Question 3

Essential gradient generator in proximal tubule

Answer 3

Na⁺/K⁺ pump

on basolateral surface

Question 4

Distinguishing feature of proximal tubule histologically

Answer 4

microvilli

increases surface area and ability to reabsorb electrolytes and water

Question 5

How much overall stuff is reabsorbed in proximal tubule?

Answer 5

about 2/3

Question 6

Na⁺ transport in proximal tubule

Answer 6

Na⁺/K⁺ ATPase on basolateral/interstitial surface

Na⁺/H⁺ antiporter on lumenal surface

Question 7

Na⁺ helps transporter what other substances in proximal tubule?

Answer 7

basolateral surface:

amino acids, glucose, phospharous

lumenal surface:

HCO₃^-

Question 8

Glucose transporters in proximal tubule

types

Answer 8

lumenal sodium-linked glucose transporters

type 1

type 2 (90%)

Question 9

What ion do glucose transporters use for secondary transport?

Answer 9

Na⁺ symporter

on lumenal surface

Question 10

T_m = transport maximum

Answer 10

glucose context

15 mM is saturation point

after 15 mM, then saturated (270 mg/dL)

Question 11

What substance assists in the moving of Cl^- across the lumenal surface in the proximal tubule?

Answer 11

formate/hydroformic acid

Question 12

Hydroformic acid/Cl^- transport

Answer 12

H⁺ + formate → HF (hydroformic acid)

HF moves into tubule cell

HF → H⁺ + formate in cell

formate/Cl^- antiporter moves chloride into tubule cell

K⁺/Cl^- symporter into interstitial space

Question 13

How does the Na⁺/H⁺ antiporter help in the transport of Cl^-?

Answer 13

H⁺ pumped out into lumen

H⁺ + formate → HF

allows HF to enter cell

then formate moves out of cell, bringing Cl^-