4/19: Renal Regulation of Potassium and Diuretics

Question 1

What and why is highly regulated?

Answer 1

ECF H+ because it alters all proteins in the body (enzymes, clotting factors, muscle contraction, channels, etc.)

Question 2

What are pH’s of normal arterial blood, venous blood, and urine pH?

Answer 2

Normal arterial blood = 7.4
Normal venous blood = 7.35
(more acidic due to higher CO2 levels)
Urine pH = varies from 4.5-8

Question 3

What are sources of hydrogen gain?

Answer 3

• Generation of H+ from CO2 (respiratory system)
• Metabolic CO2 production 20,000 mmol/day, all handled through respiratory system
• Nonvolatile acids: acids found/accumulated in ECF and are not associated with changes in CO2
• Produced from metabolism of proteins and other organic molecules
• Gain of H+ due to loss of bicarbonate (i.e. diarrhea, urine)

Question 4

What are sources of hydrogen loss?

Answer 4

• Hyperventilation (lower than normal PCO2 levels)
• Utilization of H+ in the metabolism of various organic anions
• Loss of H+ (i.e. vomit, urine)

Question 5

How are fixed/non volatile acids excreted?

Answer 5

By kidneys

Question 6

What does protein catabolism produce?

Answer 6

Sulfuric acid and HCl

Question 7

What does phospholipid catabolism produce?

Answer 7

Phosphoric acid

Question 8

What does exercise and hypoxia produce?

Answer 8

Lactic acid

Question 9

What does post-absorptive state, diabetes mellitus produce?

Answer 9

Keto acids

Question 10

What do nucleoprotein in metabolism produce?

Answer 10

Uric acid

Question 11

What are the three primary systems to regulate H+ in body fluids?

Answer 11

chemical, respiratory, kidneys

Question 12

What is the chemical system?

Answer 12

acid-base buffer system that is instantaneous.
Does not add or remove H+, but keeps it “tied up” until balance can be re-reestablished

Question 13

What is the bicarbonate buffer system?

Answer 13

Most powerful buffer for ECF. CO2 and HCO3- regulated by respiratory (carbon dioxide) and renal (bicarbonate) systems

Question 14

What happens to the bicarbonate buffer system with an increase in [CO2]ECF?

Answer 14

shifts reaction to right, leading to more bicarbonate and hydrogen ion generation. Increasing Co2 is the same as increasing H+ which decreases the pH

Question 15

Where a drop in CO2 shift the bicarbonate buffer system reaction?

Answer 15

Right, increasing the pH

Question 16

What is the phosphate buffer system?

Answer 16

Not a significant buffer for ECF. Concentration significantly lower than bicarbonate buffer system. Important for buffering renal tubular fluids and ICF

Question 17

Where does most chemical buffering occur?

Answer 17

In ICF

Question 18

What are the functions of intracellular buffers?

Answer 18

help prevent changes inside cells
- Proteins inside cell (negative, allows for hydrogen binding)
- Organic phosphates

Question 19

What are the functions of H+ entry into cells?

Answer 19

via CO2
- Produced inside cells via lactic acid and keto acids and can enter cell by a H/K exchanger (contributes to hyperkalemia)

Question 20

What does the respiratory system regulate?

Answer 20

removal of CO2 (and acid) by altering alveolar ventilation rate (Va). Occurs fast, within seconds to minutes

Question 21

How does the respiratory system control ECF CO2 levels?

Answer 21

o Resting normal human produces 200 mL of CO2 per minute (CO2 -> H+)
o CO2 transport:
- 10% dissolved in plasma
- 25% bound to Hb
- 65% converted in bicarbonate by carbonic anhydrase in RBC (via chloride/CO2 exchanger

Question 22

What is the alveolar exchange system in the body?

Answer 22

removes CO2 from the body. Can be altered to alter pH changes in the blood

Question 23

What do disorders of the respiratory system lead to?

Answer 23

Respiratory acidosis or alkalosis

Question 24

What does hyperventilation lead to?

Answer 24

lowers CO2 in blood and raises pH (respiratory alkalosis)

Question 25

What does hypoventilation cause?

Answer 25

raises Co2 in blood and lowers pH (respiratory acidosis)

Question 26

What are changes in alveolar ventilation if pH starts to fall/rise?

Answer 26

If pH starts to fall -> increase in alveolar ventilation will occur
If pH starts to rise -> decrease in alveolar ventilation will occur

Question 27

What do the kidneys excrete?

Answer 27

an acidic or alkaline urine. Most powerful of the 3 systems. Occurs slow, within hours to days

Question 28

How do the kidneys regulate pH?

Answer 28

by altering plasma bicarbonate levels
o secrete H+
o reabsorb, produce, or excrete HCO3-
- for each HCO3- reabsorbed and H+ must be secreted

Question 29

How does hydrogen ion secretion occur via?

Answer 29

secondary active transport that occurs in the proximal tubule, thick ascending limb, and early distal tubule

Question 30

How is bicarbonate titrated?

Answer 30

With H+ in tubule lumen

Question 31

Where does excess H+ excretion occur?

Answer 31

function of late distal tubule and collecting duct. Responsible for only 5% of H+ secretion, but enough to create maximally acidified urine

Question 32

What systems are used for excess H+ excretion?

Answer 32

Pi and glutamine/NH4+ systems are used for excess H+ excretion (non-volatile acids produced during metabolism)

Question 33

What does abnormal H+ production induce?

Answer 33

Renal compensation

Question 34

What happens when secreted H+ exceeds filtered load of HCO3?

Answer 34

H+ can bind to phosphate bigger

Question 35

What happens anytime H+ combined with a buffer other than bicarbonate?

Answer 35

results in new bicarbonate being added to the ECF
- Most filtered Pi reabsorbed so only a small amount of this buffer is available to interact with H+ in filtrate

Question 36

Where does the ammonia buffer system occur?

Answer 36

in proximal tubule, thick ascending limb and distal tubule

Question 37

Where is ammonia added into?

Answer 37

filtrate following glutamine metabolism and represents acid secretion

Question 38

In the collecting duct, what is ammonia secreted into?

Answer 38

lumen where it combines with H+ to form NH4+

Question 39

When ammonia is secreted into lumen, what does this result in?

Answer 39

new bicarbonate being added to the ECF