Renal Regulation of Acid/Base Balance

Question 1

normal pH of body?

Answer 1

7. 4

7. 35-7.45

Question 2

henderson hasselbalch equation

Answer 2

pH = pKa + log (H A / HA)

Question 3

buffer system depends on?

Answer 3

concentration of buffer system components

nearness of pKa to pH of solution

Question 4

phosphate buffer system

Answer 4

pKa = 6.8

Question 5

volatile acid

Answer 5

carbon dioxide acid

-can be expired via respiration

Question 6

fixed acids

Answer 6

generated metabolically
-excreted in urine

glycolysis, fatty acid oxidation

cannot be removed via respiration**

Question 7

3 lines of defense?

Answer 7

chemical buffer systems
respiration
kidneys

Question 8

extracellular buffers

Answer 8

bicarb
inorganic phosphate (H2PO4 > HPO4)
plasma proteins

Question 9

intracellular buffers

Answer 9

hemoglobin
organic phosphate (HPO4 > PO4)
bicarbonate

Question 10

bicarbonate buffer system

Answer 10

3.8 - 6.1

Question 11

pH = ?

Answer 11

6.1 + HCO3- / log (0.03 x P-CO2)

uses bicarbonate and PCO2

Question 12

why is bicarbonate buffer so powerful

Answer 12

its an open system

• too much CO2 - we can breath it out
• too much HCO3- we can excrete in kidney

Question 13

secretion of H+

Answer 13

mainly as NH4+

Question 14

renal response to excess acid?

Answer 14

HCO3- reabsorbed

H+ secreted as NH4+

Question 15

renal response to excess base?

Answer 15

incomplete reabsorption of HCO3-
decreased H+ secretion
secretion of HCO3- in collecting duct

Question 16

urinary buffers?

Answer 16

need to buffer H+ because urine can only have so many free H+ irons

Question 17

titratable acid

Answer 17

conj base of metabolic acid

-phosphate, creatinine, urate accept H+

Question 18

ammonia

Answer 18

generated by tubular epithelium

-can accept H+

Question 19

total renal H+ excretion?

Answer 19

titratable acid + ammonium - HCO3-

Question 20

HCO3- excretion?

Answer 20

equivalent to adding H+ to body fluids

Question 21

acidification of urine?

Answer 21

collecting duct, can be acidified to pH as low as 4.5

Question 22

alpha-intercalated cells?

Answer 22

actively secretes H+

H+ ATPase

HCO3-/Cl exchanger basolateral membrane
-for every H+ secreted, a HCO3- is reabsorbed

Question 23

beta-intercalated cells?

Answer 23

secretes HCO3-

-HCO3-/Cl exchanger apical membrane

Question 24

proximal tubule

Answer 24

secrete H+ to reabsorb HCO3-
-only slight fall in pH

Na/H exchanger secretes H to combine with HCO3-

H2CO3 converted to CO2 and H2O via carbonic anhydrase
-CO2 moves into cell and combines with H2O to then form bicarbonate and H+

bicarbonate then reabsorbed

**no net secretion of H+ due to this mechanism

saturable process**

Question 25

excretion of H+ as titratable acid

Answer 25

HPO2- is most important buffer

Question 26

glutamine

Answer 26

intracellularly broken down to 2x NH4+ | -produces 2x HCO3- **

Question 27

chronic acidemia

Answer 27

upregulation of NH4+ production bc they need to get rid of excess H+

Question 28

beta-intercalated cell

Answer 28

secrete bicarbonate in exchange for Cl in alkalemia**

Question 29

factors controlling renal H+ secretion

Answer 29

``` intracellular pH plasma PCO2 carbonic anhydrase activity Na reabsorption extracellular [K] aldosterone ```

Question 30

diuretic abuse

Answer 30

can cause alkalemia lower ECF volume - activates RAAS, increases aldosterone - increases sodium and secretes H+ leads to metabolic alkalosis

Question 31

acidemia

Answer 31

pH below 7.35

Question 32

acidosis

Answer 32

condition resulting in acidemia

Question 33

alkalosis

Answer 33

condition resulting in alkalemia

Question 34

alkalemia

Answer 34

arterial pH above 7.45

Question 35

respiratory acidosis

Answer 35

increased PCO2 renal response -increased H+ secretion

Question 36

respiratory alkalosis

Answer 36

decreased PCO2 renal response -less H+ secretion

Question 37

chronic

Answer 37

24-48 hours

Question 38

respiratory acidosis/alkalosis

Answer 38

can be compensated completely by kidneys

Question 39

metabolic acidosis

Answer 39

``` gain fixed acid also diarrhea (lose HCO3-) ``` respiratory compensation - increased ventilation renal compensation - increased H+ secretion as ammonium mainly and HCO3- production

Question 40

metabolic alkalosis

Answer 40

excessive gain of strong base or HCO3- vomiting - lose fixed acid (gastric acid) respiratory compensation - decreased ventilation renal compensation - incomplete reabsorption of HCO3- and beta-intercalated secrete HCO3-

Question 41

diarrhea

Answer 41

metabolic acidosis

Question 42

vomiting

Answer 42

metabolic alkalosis

Question 43

anion gap

Answer 43

Na - (Cl + HCO3-) used in DDx of metabolic acidosis -gap is unmeasured anion greater than around 18 is abnormal

Question 44

hyperchloremic acidosis

Answer 44

anion gap is unchanged | -loss of HCO3- matched by gain in Cl-

Question 45

high anion gap acidosis

Answer 45

anion gap increase - HCO3- replaced by unmeasured anion - lactate, ketoacidosis, poisoning - ethanol, antifreeze, aspirin, etc.