Unit 2, L20 Acid Base 2

Question 1

Define NEAP

Answer 1

Net Endogenous Acid Production, and it is an equivalent loss of HCO3 from the body that must be replaced

Question 2

For acid base balance to be maintained

Answer 2

Acid must be excreted from the body at a rate equivalent to its addition

Question 3

What is the amount of nonvolatile acids that is added to the body each day for a meat-containing diet, normal metabolism, and fecal HCO3 loss?

Answer 3

50-100 mEq/day for most adults

Question 4

How are nonvolatile acids neutralized by bicarb?

Answer 4

Nonvolatile acids are immediately neutralized by bicarb in the ECF

Question 5

To maintain acid-base balance, the kidneys must do what?

Answer 5

The kidneys must replenish the bicarb lost by neutralization of nonvolatile acids, a process called Renal Net Acid Excretion (RNAE)

Question 6

Which is regulated, NEAP or RNAE?

Answer 6

RNAE, NEAP is not regulated

Question 7

What will happen when the kidneys regulate RNAE

Answer 7

1) Replenish the HCO3 (new HCO3) lost by neutralization of nonvolatile acid
2) Kidneys must prevent loss of HCO3 in urine

Question 8

How much does the PT reabsorb of bicarb

Answer 8

80%

Question 9

How much does the TAL reabsorb for bicarb

Answer 9

10%

Question 10

What is the excretion of bicarb?

Answer 10

0%

Question 11

How much bicarb do we need each day?

Answer 11

50-100 mEq

Question 12

How much H is secreted and what happens to it?

Answer 12

Nephrons secrete out about 4400 mEq and most of it will reabsorb the filtered load of bicarb

Question 13

What is the predominant pathway for H secretion in the PT

Answer 13

NHE3 transporter, it is an Na/H exhanger, sends Na in and H out on the apical membrane q

Question 14

What are the two different isoforms of CA and how do they function

Answer 14

1) CA-IV is present on the brush boarder, so the CO2 and H2O formed readily cross the luminal membrane and enter the cell
2) Ca-II is inside the cell, and this is where H and bicarb are produced

Question 15

HCO3 is reabsorbed by two mechanisms in the PT, what are they

Answer 15

1) Na-HCO3 cotransporter, also called NBC1

2) Cl-HCO3 exchanger

Question 16

In the PT, is there increased, decreased, or net reabsorption of Na and HCO3?

Answer 16

Net reabsorption

Question 17

In the DT, bicarb is being reabsorbed by what transporter

Answer 17

AE1, moves bicarb out towards the blood and Cl into the cell

Question 18

In the PT, is there H secretion?

Answer 18

No

Question 19

In the DT, is there H secretion?

Answer 19

Yes, we have secretion from the alpha intercalated cells

Question 20

In the distal tubule, for each H that is being secreted, what is happening with bicarb

Answer 20

For each H that is being excreted as titratable acid, one new HCO3- is being synthesized and reabsorbed

Question 21

PT vs DT in terms of H secretion and bicarb

Answer 21

PT: No H acid secretion, and reabsorption of bicarb
DT: H excreted, bicarb synthesis, and reabsorption of bicarb

Question 22

Beta intercalated cells will secrete what

Answer 22

Bicarb, not H

Question 23

In the DT, bicarb is secreted through what transporter

Answer 23

Pendrin, it sends bicarb out and Cl into the cell

Question 24

How is H reabsorbed in DT

Answer 24

V-ATPase will reabsorb H

Question 25

Under meat-containing diets, what will dominate, H secretion or bicarb secretion?

Answer 25

H secretion will dominate

Question 26

How much acid is normally excreted in urine?

Answer 26

50-100 mEq of acid, so urine is normally acidic

Question 27

H can be removed in what two main forms

Answer 27

1) Titratable acids in the urine | 2) NH4

Question 28

What is the most important titratable buffer and why?

Answer 28

Phosphate, because of its relatively high concentration in urine and its ideal pKa

Question 29

What is the percentage of Pi that is reabsorbed and excreted?

Answer 29

85% reabsorbed, 15% excreted

Question 30

What is a titratable acid

Answer 30

Since urinary pH is bounded over the range of 7.4 to 4.4, only those weak acids with pKas within this range are titrable acids

Question 31

What is ammonium and why is it in our urine?

Answer 31

Hydrogen ions that are not associated with Pi or other filtered bases are excreted as ammonium, and more H ions are excreted with ammonium than with filtered bases like Pi

Question 32

NH4 production and its relationship with bicarb

Answer 32

NH4 is produced by the kidneys and its synthesis and subsequent excretion adds HCO3 to the ECF, and this is regulated in response to the acid-base requirements of the body

Question 33

At pH 7.3, what form is ammonia in and because of this, what is the consequence for H

Answer 33

NH4 form, so ammonium, and H can be excreted

Question 34

What is ammoniagenesis

Answer 34

Production of NH4 from glutamine in the PT

Question 35

New bicarb is produced how

Answer 35

During the metabolism of glutamine by cells of the PT

Question 36

What is critical for the excretion of NH4?

Answer 36

H secretion by the CD is critical for the excretion of NH4

Question 37

If there is no H secretion, what happens to NH4

Answer 37

NH4 will be returned to the systemic circulation, converted to urea in the liver, and consume bicarb

Question 38

What is the overall net result with bicarb and ammonium

Answer 38

1 new bicarb is returned to the systemic circulation for each proton excreted in the form of NH4 in the urine

Question 39

What are the three quantities to consider when examining the net excretion of acid?

Answer 39

The amount of titratable acidity The amount of ammonium The amount of bicarbonate or free protons, if any

Question 40

The steps to excrete a base

Answer 40

1) Freely filter bicarb 2) Reabsorb the majority of the filtered bicarb 3) Reabsorb some additional bicarb 4) Secrete some bicarb 5) Excrete alkaline urine containing bicarb

Question 41

The steps to excrete an acid

Answer 41

1) Freely filter bicarb 2) Reabsorb the majority of the filtered bicarb 3) Reabsorb some additional bicarb 4) Secrete H and secrete NH4 5) Excrete acidic urine containing NH4

Question 42

What is the equation for quantifying RNAE

Answer 42

RNAE = titratable acid excreted + NH4 excreted - HCO3 excreted

Question 43

What will increase H secretion

Answer 43

Cellular acidosis Endothelin Cortisol Ang II

Question 44

What will increase ammoniagenesis

Answer 44

Cellular acidosis Cortisol Ang II

Question 45

What will decrease Pi reabsorption

Answer 45

PTH

Question 46

What will increase new bicarb synthesis

Answer 46

Titratable acid (Pi) NH4 excretion Rhbg and Rhcg

Question 47

ECF volume expansion will do what for regulation of bicarb

Answer 47

ECF volume expansion will inhibit isosmotic reabsorption in the PT, which will inhibit bicarb reabsorption

Question 48

ECF volume contraction will do what for regulation of HCO3

Answer 48

WIll stimulate bicarb reabsorption

Question 49

Ang II will do what for regulation of bicarb

Answer 49

Stimulates Na-H exchange in the PT, which will stimulate bicarb reabsorption and increase blood bicarb concentration. This can cause contraction alkalosis, which can also be caused by loop diuretics or thiazide diuretics

Question 50

Effect of the lungs on bicarb

Answer 50

Chronic changes in PCO2 alters the reabsorption of filtered bicarb Increases in PCO2 increases the reabsorption of bicarb and decreases the PCO2 will decrease the reabsorption of bicarb

Question 51

ET-1 will do what for H transport in the PT

Answer 51

Stimulate the insertion of Na/H antiporter into the apical membrane, and insertion of Na/3HCO3 symporter into the basolateral membrane in PT

Question 52

Cortisol will do what for cellular H transport in the PT

Answer 52

Increase the abundance of the Na/H antiporter and Na/3HCO3 symporter in the PT

Question 53

Ang II will do that for cellular H transport in the PT

Answer 53

Bind to the ang I receptor, stimulate H secretion and bicarb reabsorption by the PT