Lecture 3- Renal Transport Flashcards Preview

Physiology Renal > Lecture 3- Renal Transport > Flashcards

Flashcards in Lecture 3- Renal Transport Deck (31):
1

How much fluid does the kidney filter per day?

180 L

2

>99% of filtered

water, Na, Cl, and HCO3

3

100% of filtered

glucose are reabsorbed

4

Facilitated diffusion

-passive movement of solute
- i.e. glucose transport

5

Coupled transport

-movement of two solutes. couples
- cotransport: solutes move in same direction (Na/glucose cotransporter)
-antiport: solutesmove in opposite direction (Na/H antiporter)

6

active transport

movement of solute up a concentration gradient
-require input of energy
-Na/K ATPase

7

endocytosis

invagination of region of plasma membrane
-captures material in extracellular space
-internalize material w/in endosome then traffic to lysosome for degradation

8

transcellular

through apical surface; through cell into basolateral surface

9

paracellular

between cells via junction (i.e. water and solutes -- solvent drag)

10

Transport in the proximal tubule

67% of Na, Cl, and water is reabsorbed into PT
-reabsorption is iso-osmotic since reabsorption of water follows uptake of solutes
-primary driving force for transport = Na/K ATPase
(low cytoplasmic Na concentration in tubular cells)

11

First Half of the Proximal Tubule
(Na+ Reabsorption Coupled to HCO3- Reabsorption)

1. Na+ crosses apical membrane via Na+/H+ antiporter

2. Lumenal H+ facilitates HCO3- uptake

3. Cytoplasmic CO2 converted to H+ and HCO3- by carbonic annhydrase (CA)

4. Cytoplasmic HCO3- crosses basolateral membrane via Cl-/HCO3- exchanger and Na+/HCO3- cotransporter

5. CA inhibitors at as diuretics

12

First Half of the Proximal Tubule
Na+ Reabsorption Coupled to Sugar and Amino Acid

1. Low cytoplasmic Na+ drives uptake of sugars and amino acids across apical membrane via Na+-coupled cotransporters

2. Sugars and amino acids cross the basolateral membrance via passive transport

13

Cystinuria

caused by loss of a Na-coupled amino acid transporter (characterized by kidney stones)

14

Second Half of the Proximal Tubule

1. Na+ moves across apical membrane via Na+/H+ antiporter
2. H+ re-enter from lumen by combining with anions (i.e. formate)
3. Anions recycled to lumen via Cl-/anion exchanger (also allows for Cl- uptake)
4. Cl- crosses basolateral membrane via K+/Cl- cotransporter
5. Cl- also leaves lumen by paracellular pathway: transepithelial membrane potential (lumen positive); additional Na+ reabsorption

15

Thin Descending portion of loop of Henle

HIGHLY permeable to WATER
(allows extensive water reabsorption)

16

Thick Ascending portion of loop of Henle

IMPERMEABLE to water but permeable to Na and Cl (allows salt reabsorption)

17

Thick Ascending Loop of Henle

Na/K+/Cl- transporter
-driven by Na gradient
-electroneutral
-inhibited by furosemide (loop direutic)
-K+ exits lumen, creating lkumen positive trans epithelial potential that drives paracellular uptake of cations

18

High ADH
(distal and CD)

high water permeability > extensive reabsorption of water > concentrate urine

19

Low ADH
(distal and CD)

low water permeability > extensive excretion of water > dilute urine

20

Early Part of Distal Tubule

-Impermeable to water
-Na+ and Cl- reabsorbed via Na+/Cl- cotransporter (inhibited by thiazide diuretics)
-Na+ crosses basolateral membrane via Na+/K+ ATPase
-Cl- crosses basolateral membrane via Cl- channels

21

Principal Cells

absorb Na+ via apical Na+ channels

22

Principal Cells of Late Distal Tubule and CD

-Na+ channels inhibited by amiloride diuretics
-Principal cells have K+ channels, allowing secretion into lumen
-Principal cells have ADH-sensitive water channels that help w/ reabsorption

23

Liddle's Syndrome

mutation in Na+ channel > ↑ reabsorption > ↑ BP

24

Diabetes Insipidous

no ADH response

25

Intercalated cells of Late Distal Tubule and CD

-a-intercalated cells have apical proton pump (V-ATPase) that pumps H+ into the lumen
-a-intercalated cells also have basolateral HCO3-/Cl- exchanger

26

vacuolar H+ ATPase (V-ATPase)

Responsible for H+ secretion into a-intercalated cells in DT and CD

27

renal tubule acidosis

Responsible for H+ secretion into a-intercalated cells in DT and CD
Genetic defects in renal specific isoforms of certain subunits

28

Agents that Increase NaCl and/or Water Reabsorption by the Renal Tubule

LOOK AT CHART

29

antidiruretic hormone (ADH)

stimulated by: low BP/volume or increased plasma osmolarity
Site: DCT/CD
no effect on NaCl
increases water reabsorption

30

starling forces

Movement of water (and solutes) into blood is favored by Pi and (pi)c and opposed by Pc and (pi)I

31

increase GFR

increase filtration of blood = increase protein concentration in blood in peritubular capillaries= increased movement of water (and solutes) into blood and decreased backleak into tubular fluid

*prevents large changes in Na excretion when GFR changes*