Tub Transport (lec 11)

Question 1

Filtered Load (FL) is what?

FL eqn?

Answer 1

amount of material in glom filtrate

FL = (GFR)(Px)

Question 2

Excretion rate (ER) is what?

ER eqn?

Answer 2

amount of material lost in urine

ER = (Ux)(V)

Question 3

Transport rate (Tx) is?

Tx eqn?

Answer 3

amount of material added (secrete)
or removed (reab) from glom filtrate

Tx = FL - ER

Question 4

If Tx is positive if?

Negative if?

Answer 4

Reabsorption: material removed from filtrate

Secretion: material added to filtrate

Question 5

Fractional Excretion (FE) is?

FE eqn?

Answer 5

fraction of filtered mass represented by excreted mass

FE = ER/FL

Question 6

FE is 1 if?

Answer 6

Reab: material removed from filtrate

Sec: material added to filtrate

Question 7

Paracellular Reabsorption route?

Answer 7

b/w leaky epith cells

Question 8

Transcellular Reabsorption route?

Answer 8

Luminal membrane -> baso membrane

Question 9

Transcellular Transport: simple diff via?

Facilitated diff via?

Answer 9

pores

carrier proteins

Question 10

Transcellular Transport: º active transport?

2º active transport?

Other transport?

Answer 10

Na+/K+ATPase
H+, H+/K+, Ca2+ ATPases

coupled to Na+ gradient

endocytosis

Question 11

Na+/K+ATPase pump where?

Answer 11

on basomem:
Na+ out to interstitium
K+ into cell from interst

Question 12

Glucose transport route/mechanism?

Answer 12

Follows Na+ gradient from lumen into cell (2ºactive)

From cell to interstit (fac diff)

Question 13

Tubular Reab in Proximal Tubule: Na+?

Answer 13

67%

from lumen to PT cell via:
co-trans w/ organics
and Na+/H+ exg

From cell to interst via:
Na+/K+ATPase
or cotrans w/ HCO3-

Question 14

Tubular Reab in Proximal Tubule: H2O?

Answer 14

H2O reab: 65%, passive Na+-linked

Question 15

Tubular Reab in PT: Cl-

Answer 15

Paracellular (thru leaks)

Question 16

Tubular Reab in Proximal Tubule: Na+

Ang II affects how?

SNS?

Parathyroid Hormone?

Answer 16

Ang II: stim Na+/H+ exg

SNS: stim Na+ reab

PTH: inhib Na+-phosphate cotrans,
stim urine excretion of phosphate

Question 17

Tubular Reab in Proximal Tubule: Na+

Osmotic Diuresis affects how?

Answer 17

Excess unreab solute (e.g. mannitol, glu) inhibits osm flow of H2O from lumen to baso

Causes Na+ diff back into lumen ->
↑ Na+ and H2O loss

Question 18

Tubular Reab in LOH:

Na+

H2O

Answer 18

Na+ reab: 25%, active

H2O reab: 15%, passive Na+-linked

Question 19

Tubular Reab in Distal/Collecting Tubule:

Na+

H2O

Answer 19

Na+ reab: 8%, active via aldosterone

H2O reab: 20%, passive via ADH

Question 20

TF:[plasma] in PT ?????

Answer 20

slide 16?

Question 21

TF/Px = 1 if?

Answer 21

reab of x exactly proportional to H2O reab

Question 22

TF/Px < 1 if?

Answer 22

reab of x greater than H2O reab

Question 23

TF/Px > 1 if?

Answer 23

reab of x less than H2O reab

OR net secretion of x

Question 24

TF/Pinsulin used as marker why?

Answer 24

[insulin] determined by mvmt of H2O only

since filtered only

Question 25

Tubular Maxim (Tm) is?

Answer 25

max rate of transport of particular substance,
point where transport proteins are saturated,
(U) in PT

Question 26

What happens at transport rates below Tm?

Answer 26

all the filtered load is reabsorbed

Question 27

What happens at transport rates above Tm?

Answer 27

portion of load above Tm is excreted

Question 28

Tm for glucose????

Answer 28

slide 19??

Question 29

Effect of higher GFR on Tglu?

Lower GFR?

Answer 29

higher the GFR, lower the threshold before glu spills

Lower GFR, higher threshold

Question 30

Other solutes w/ Tm’s?

Answer 30

sugars
AA/proteins
metabolic intermediates
phosphate ions
vitamins

Question 31

Methods of Tubular Secretion?

Answer 31

NON-SPECIFIC
Anions, Cations have separate transport
Paracellular
Transcellular

Question 32

What compounds are secreted?

Answer 32

metabolites, waste, foreign chemicals

Question 33

Tubular Secretion: Anions?

Answer 33

tertiary active transport
shared by all anions =
high Px inhibits secretions of non-x anions

Question 34

Role of PAH in secretion?

Answer 34

is anion ->

can inhibit secretion of other anions