Renal: Acid Base balance

Question 1

how do most proteins interact with H+

Answer 1

serve as buffers attenuate pH changes without altering total body pH

Question 2

how do H+ ions come about in the body?

Answer 2

metabolically produced

consumed by food, drugs, etc…

Question 3

How do the lungs impact H+ ?

Answer 3

add or remove H+ by adding/removing CO2 via ventilation

Question 4

What other organs regulate H+ ?

Answer 4

kidney

GI tract

Question 5

what pathologies alter H+ levels?

Answer 5

vomitting – loss of H+ (higher pH = alkalosis)

diarrhea — gain of H+ (lowers pH = acidosis)

Question 6

what is the importance of H2CO3 (carbonic acid)?

Answer 6

it’s an intermediate that can increase or decrease the pH.

Question 7

why is CO2/HCO3 important?

Answer 7

important buffer that can maintain H+ level by simply breathing

Question 8

how much HCO3 is filtered by the body?

Answer 8

4.3 mol/day

GFR x [HCO3 level]

Question 9

Equivalence of bicarbonate loss and acid gain (and vice versa): formula

Answer 9

CO2 + H2O H+ + HCO3-

Question 10

in regards to HCO3, how is neutrality accomplished?

Answer 10

all bicarb (HCO3) must be reabsorbed

Question 11

in regards to HCO3, how is alkalemia (high pH) corrected?

Answer 11

HCO3 must be secreted

Question 12

in regards to HCO3, how is acidemia (low pH) corrected?

Answer 12

HCO3 must be produced

Question 13

what enzyme accelerates the production of HCO3?

Answer 13

carbonic anhydrase (H2CO3)

Question 14

How does reabsorption of HCO3 in the PT occur?

Answer 14

filtered HCO3– first interacts with H+, and makes CO2. CO2 is neutral and enters PT cells. Intracellular CO2 is then hydrated and produces H+ and HCO3–. H+ is secreted to the lumen via NHE, while HCO3 is reabsorbed. Mechanistically, it is H+ and CO2 that are moving through the apical membrane, but the overall result is HCO3– reabsorption.

NOTE: Mechanistically, it is H+ and CO2 that are moving through the apical membrane, but the overall result is HCO3- reabsorption.

Question 15

what ion impacts HCO3 reabsorption in the TAL?

Answer 15

Cl

Question 16

if HCO3 needed to be added to the blood in the distal portions of the nephron, how would this occur?

Answer 16

HCO3 is made from CO2 hydration in type A intercalated cells

–new HCO3 to blood and new H+ to tubule lumen

Question 17

what is the other type of intercalated cell? what is it’s function?

Answer 17

a. type b intercalated

b. secrete HCO3 into lumen and absorb H+. into blood (opposite of type a)

Question 18

what are considered titratable acids?

Answer 18

phosphates and sulfates (by H+ secrection from intercalated cells in CD)

Question 19

if phoshate can only titrate 40 mmol/day of acid out of 50 -100 mMol/day (net acid production). What does the rest?

Answer 19

ammonia

NH3

Question 20

how is nitrogen metabolized in the liver?

Answer 20

NH4 associates with HCO3 and makes either urea or glutamine

Question 21

how is nitrogen metabolized in the kidney?

Answer 21

Urea is excreted, while glutamine is metabolized to produce NH4+ and HCO3- in the PT
NH4+ is then excreted, while HCO3- and glucose are returned to the body

Question 22

what regulates nitrogen becoming urea or glutamine?

Answer 22

In acidosis more NH4+ is incorporated into glutamine

In alkalosis more NH4+ is incorporated into urea

Question 23

in acid/base regulation in the kidney, what happens if plasma is acidic?

Answer 23

(PT/TAL) Secrete H+ —-Save all HCO3

(CD) Secrete H+ by intercalated A cells

Excrete H+ —- as NH4+ and as H2PO4-

Thus, urinary pH is low
(lowest attainable pH = 4.4)

Question 24

in acid/base regulation in the kidney, what happens if plasma is alkaline?

Answer 24

(PT/TAL) Retain some H+ — Do not save all HCO3

(CD) Secrete HCO3- by intercalated B cells

Turn nitrogen into urea (rather than into NH4+)

Excrete HCO3-

Thus, urinary pH is high (> 7.4)

Question 25

what happens in respiratory acidosis?

Answer 25

increased H+ (lower pH)
increased HCO3
increased CO2

caused by changes in plasma CO2

Question 26

what happens in respiratory alkalosis?

Answer 26

decreased H+ (higher pH)
decreased HCO3
decreased CO2

caused by changes in plasma CO2

Question 27

What happens in metabolic acidosis

Answer 27

increased H+ (lower pH)
decreased HCO3
decreased CO2

caused by changes in plasma HCO3

Question 28

What happens in metabolic alkalosis?

Answer 28

decreased H+ (high pH)
creased HCO3
increased CO2

caused by changes in plasma HCO3

Question 29

what is renal response to respiratory acid/base imbalance?

Answer 29

raise plasma HCO3- in response to respiratory acidosis

reduce plasma HCO3- in response to respiratory alkalosis

Question 30

what is respiratory respsonse to metabolic acid/base imbalance?

Answer 30

remove CO2 in response to metabolic acidosis

retain CO2 in response to metabolic alkalosis