Test 2: Wk7: 2 Tubular transport of K/Ca/Mg - Mangiarua

Question 1

Plasma K conc.

Range

Answer 1

4 meq/L

3.4-4.5 meq/L

Question 2

fatal plasma K conc.

Answer 2

8 meq/L

Question 3

Intracellular K conc.

Answer 3

145 meq/L

Question 4

primary regulator of K

Answer 4

kidneys

Question 5

K transport is

Answer 5

bidirectional

Question 6

% K reabsorbed in proximal tubule

Answer 6

67%

Question 7

% K reabsorbed in thick ascending limb

Answer 7

20%

Question 8

% K remaining at start of distal convoluted tubule

Answer 8

13%

Question 9

% of filtered K is reabsorbed prior to distal tubule regardless of dietary K

Answer 9

87%

Question 10

K has a — reabsorption

Answer 10

net

Question 11

proximal tubule K transport

Answer 11

active - pump on luminal and basolateral

passive - most reabsorption in PT is passive

Question 12

Distal tubule and cortical collecting duct K transport

Answer 12

perform the fine-tuning of K+ excretion to

maintain K+ balance

Question 13

a person on a low K+ diet, there is further reabsorption of K+ by the — of the late distal tubule and collecting ducts

Answer 13

α-intercalated cells

Question 14

persons on a normal or high K+ diet, K+ is secreted by the — of the late distal tubule and collecting duct

Answer 14

principal cells

Question 15

The principal cells, in the connecting tubule and cortical and medullary collecting duct, when stimulated by — will secrete —.

Answer 15

aldosterone

K+

Question 16

— dominate the overall transport of K+ unless — is inhibited

Answer 16

Principal cells

Aldosterone

Question 17

— secretion is increased by Na entrance through —

Answer 17

K; ENaC

Question 18

sodium entrance through ENaC sodium
channels causes (2)

Answer 18

1. NA,K-ATPase stimulation

2. Depol of luminal membrane

Question 19

Potassium entering via the Na,K-ATPase that is not secreted

Answer 19

recycles through basolateral channels.

Question 20

amiloride inhibits

Answer 20

inhibits sodium entry, and therefore inhibits potassium

secretion

Question 21

stimulates both sodium reabsorption and potassium secretion at multiple points.

Answer 21

Aldosterone

Question 22

ROMK and BK Low K excretion

Answer 22

ROMK - sequestered

BK - closed

Question 23

ROMK and BK Normal K excretion

Answer 23

ROMK - open

BK - Closed

Question 24

ROMK and BK High K excretion

Answer 24

ROMK - open

BK - open

Question 25

5 factors that alter K secretion

Answer 25

(1) Sodium Delivery to the Distal Nephron (2) Aldosterone (3) Plasma Potassium (4) GI Hormones (5) Angiotensin II

Question 26

Sodium Delivery to the Distal Nephron on K secretion

Answer 26

High sodium delivery stimulates potassium secretion; low | sodium delivery inhibits it.

Question 27

Aldosterone on K secretion

Answer 27

Increases Na-K-ATPase which supplies more potassium from the interstitium to the cytosol of the principal cells. Stimulates the activity of ROMK channels in principal cell of the distal nephron

Question 28

Plasma Potassium on K secretion

Answer 28

The Na-K-ATPase that takes up potassium in principal cells is highly sensitive to the potassium concentration Plasma potassium concentration exerts an influence on potassium excretion but is not the dominant factor under normal conditions.

Question 29

GI Hormones on K secretion

Answer 29

Gastrointestinal peptide hormones released in response to ingested potassium may be responsible for the response to dietary intake.

Question 30

Angiotensin II on K secretion

Answer 30

Inhibitor of potassium secretion; decrease the activity of ROMK channels in principal cells.

Question 31

Alkalosis results in --- K from principal cells which leads to ---

Answer 31

⬆ K secretion and depletion of K

Question 32

elevated plasma pH is often associated with

Answer 32

hypokalemia.

Question 33

Low plasma pH is often associated with

Answer 33

hyperkalemia

Question 34

Total plasma calcium has 3 components

Answer 34

1. 40% protein bound - no filter 2. 50% ionized Ca and biologically active - filters 3. 10% complexed with anions - filters

Question 35

As the plasma H+ concentration increases, the concentration of ionized calcium ---

Answer 35

increases

Question 36

In acidosis, as more H+ are buffered by plasma proteins, bound calcium is displaced from proteins causing plasma Ca to

Answer 36

increase

Question 37

in alkalosis the release of H+ from plasma proteins causes the plasma Ca to

Answer 37

decrease

Question 38

% of filtered Ca reabsorbed

Answer 38

98-99%

Question 39

PTH --- Ca++ reabsorption in the kidney and increases [Ca++ ]ECF

Answer 39

increases

Question 40

Ca paracellular reabsorption in proximal tubule

Answer 40

driven by solvent drag

Question 41

Ca transcellular reabsorption in proximal tubule

Answer 41

uptake across the brush border via Ca permeable ion channel and exit across basolateral membrane via Ca ATPase

Question 42

Ca reabsorption in thick ascending limb

Answer 42

paracellular - driven by the transepithelial electrochemical gradient

Question 43

Ca reabsorption in distal tubule

Answer 43

transcellular 1 Ca enter through apical Ca ion channels 2 Ca binds calbindin and complex diffuses across the cell to deliver Ca to basolateral 3 Ca transported across basolateral by 3NaCa antiporter and Ca-ATPase

Question 44

distal tubule is the site of Ca

Answer 44

Ca reabsorption regulation

Question 45

--- regulates calcium homeostasis

Answer 45

PTH

Question 46

PTH action

Answer 46

increases plasma Ca conc.

Question 47

PTH renal effects (3)

Answer 47

1. promotes calcitriol formation 2. increase Ca reabsorption 3. increase phosphate excretion

Question 48

PTH increases Ca++ reabsorption by: (2)

Answer 48

Increasing the transcription and open probability, and inhibition of endocytosis of the Ca++-permeable ion channel. - Upregulating the expression of calbindin and NCX1.

Question 49

% of plasma phosphate is unbound and --- filtered

Answer 49

90%; freely

Question 50

% of the filtered load of phosphate is ---

Answer 50

90%; actively reabsorbed from the nephron

Question 51

phosphate is Co-transported with Na+ across --- driven by ---

Answer 51

the luminal plasma membrane. intracellular Na+ gradient.

Question 52

Pi is reabsorbed via three sodium phosphate cotransporters

Answer 52

Npt2a, Npt2c and PiT-2.

Question 53

sodium phosphate cotransporters, which are positioned in the --- of ---

Answer 53

apical membrane of renal proximal tubule cells

Question 54

PTH inhibits reabsorption of phosphate in the

Answer 54

the proximal tubule

Question 55

PTH stimulates the removal of --- from the brush border of the ---

Answer 55

NPT2; proximal tubule

Question 56

% of plasma magnesium is protein bound

Answer 56

30% of plasma magnesium is protein bound ➞ non filterable.

Question 57

% of plasma magnesium is ionized

Answer 57

60% of plasma magnesium is ionized ➞ filterable.

Question 58

% of plasma magnesium is complexed to anions such as phosphate, citrate, and oxalate

Answer 58

10% of plasma magnesium is complexed to anions such as phosphate, citrate, and oxalate➞ filterable.

Question 59

Mg reabsorption in proximal tubule is believed to be

Answer 59

paracellular aided by a chemical gradient generated by Na gradient

Question 60

Mg reabsorption in Thick ascending limb

Answer 60

paracellular

Question 61

Mg2+ reabsorption along the DCT, which is predominantly ---

Answer 61

transcellular

Question 62

Mg2+ entry across the DCT apical membrane may take place via the

Answer 62

TRPM6 cation channel; the key driving force is the inside-negative membrane potential.