Proximal Tubular Function and Renal Clearance

Question 1

What 2 processes of the Proximal tubule aid in homeostatis?

Answer 1

Rebasorption of useful substances - movement from tubule lumen to blood
Secretion of less useful substance - from blood to tubule lumen

Question 2

What is the function of Proximal tubule?

Answer 2

Reclaims useful filtered substances

Most reabsorption occurs here of H2o and Solutes and NA+ transporters

Question 3

What Na+ transporters are involved with reabsorption of PCT?

Answer 3

Na+ symporters and antiporters

Question 4

What are Symporters?

Answer 4

2 or more solutes cross membrane in same direction

Question 5

What are antiporters?

Answer 5

2 or more solute cross membrane in opposite direction

Question 6

What are Na+ transporters used for?

Answer 6

Energy is derived indirectly from ATP used in 1 active transport

Question 7

What is Transport Maximum? what is symbol?

Answer 7

Tm - transporters have upper capacity limit in mg/min

Question 8

What does solute reabsorption drive?

Answer 8

H2o absorption

Question 9

How does H2O absorption occur?

Answer 9

Via osmosis

Question 10

What happens with H2O reabsorption in the Proximal tubule?

Answer 10

H2O reabsorbed with solutes = obligatory

Question 11

What happens with H20 reabsorption in the Collecting duct?

Answer 11

H20 reabsorption needs to be driven = facultative

Question 12

Where does reabsorption occur from the Lumen into?

Answer 12

Peritubular capillary

Question 13

How does the Capillary uptake work?

Answer 13

Forces favouring uptake = forces opposing uptake

Question 14

What do Na transporters achieve in reabsorption?

Answer 14

near 100% reabsorption of organic solutes (glucose, AA)
80-90% Bicarb
65% H20,Na,K
50% Cl
varies with Ca,Mg,Phosphate

Question 15

What is the Na/K pump located?

Answer 15

Basolaterally in the kidney

Question 16

What does the Na-K pump do and use?

Answer 16

Uses ATP to keep intracellular Na low

Drives secondary transport of - Glucose,AA,Bicarb,Chloride

Question 17

What kinds of substances are secreted?

Answer 17

small and filtered substances

Para-aminohippuric acid

Question 18

What transport is required for secretion?

Answer 18

Active transport

Question 19

What happens with Para-amnohippuric acid?

Answer 19

Freely filtered, limited Tm secretion, Not reabsorped, indicator of renal blood flow

Question 20

What is renal clearance?

Answer 20

Volume of plasma cleared of a substance in a given time

Question 21

What is renal clearance of x?

Answer 21

filtration of (x) + secretion of (x) - reabsorption of (x)

Question 22

What is clearance ml/min of?

Answer 22

Urine conc x urine flow / plasma conc

Question 23

What is Inulin?

Answer 23

A polysaccharide
freely filtered
not reabsorbed or secreted

Question 24

What can inulin clearance be used to work out?

Answer 24

GFR= Uinulin x V/ P inulin

Question 25

What is a disadvantage of inulin?

Answer 25

Has to be infused

Question 26

What is a disadvantage of creatinine?

Answer 26

Is endogenous, no infusion needed, small amount secreted

Question 27

What is creatinine a by-product of?

Answer 27

Muscle metabolism

Question 28

When is GFR more accurate?

Answer 28

When subject is at rest