Renal Physl 18

Question 1

What takes care of the majority of pH disturbances?

Answer 1

Buffer systems and ventilation

Question 2

What are the two ways kidneys can alter pH?

Answer 2

• Reabsorption or excretion of H+

* Modifying HCO3- reabsorption or excretion

Question 3

How is H+ affected by the kidneys during acidosis?

Answer 3

The kidneys secrete H+ into tubule lumen

Question 4

What are buffers in the kidneys?

Answer 4

Ammonia from amino acids, and phosphate ions (HPO4 2-)

Question 5

What are large amounts of hydrogen ions trapped as in the kidneys?

Answer 5

NH4+ and H2PO4- which is excreted

Question 6

What do the buffers in the kidneys help with?

Answer 6

Excretion of H+ excretion by binding to them in the lumen

Question 7

What do the kidneys generate during the excretion of H+ ions?

Answer 7

Bicarbonate ions from carbon dioxide and water

Question 8

What can the carbon dioxide and water produced in the kidney do?

Answer 8

Go into the bloodstream and act as a buffer and help increase pH

Question 9

What happens in the kidneys during alkalosis?

Answer 9

HCO3- is secreted and H+ is reabsorbed to help restore pH

Question 10

How long do renal response to acidosis or alkalosis take?

Answer 10

24-48 hours

Question 11

What does the apical Na+-H exchanger do?

Answer 11

Brings sodium into the cell and H+ into the lumen against its concentration gradient

Question 12

What does the Basolateral Na+- HCO3- symporter do?

Answer 12

Moves Na+ and HCO3- out of the cell and into the interstitium. Using the energy from bicarbonate moving down its concentration gradient

Question 13

What does H+ ATPase (proton pump) do?

Answer 13

Pumps H+ into the lumen of distal nephron against its concentration gradient

Question 14

What does the H+ K+ ATPase do?

Answer 14

Pumps H+ into urine in exchange for K+ and can contribute to potassium homeostasis

Question 15

What does the Na+ NH4+ antiporter do?

Answer 15

Puts NH4+ into the lumen in exchange for Na+

Question 16

What part of the nephron plays an important role in hydrogen secretion and bicarbonate reabsorption?

Answer 16

The proximal tubule

Question 17

What happens to most of the bicarbonate that is filtered by the kidneys?

Answer 17

It is reabsorbed to maintain the body’s buffer systems

Question 18

Which tubule reabsorbs most bicarbonate?

Answer 18

The proximal tubule

Question 19

What two ways does the proximal tubule reabsorb bicarbonate?

Answer 19

• Filtered bicarbonate is converted into carbon dioxide which is then converted back into bicarbonate for reabsorption
• Using the amino acid glutamine

Question 20

Why does the proximal tubule need to reabsorb bicarbonate indirectly?

Answer 20

Because there is no apical membrane transporter

Question 21

How is filtered bicarbonate is converted into carbon dioxide which is then converted back into bicarbonate for reabsorption?

Answer 21

• Hydrogen is secreted from the proximal tubule epithelial cell into the lumen opposite of sodium which is pumped into the cell using the Apical Na+-H+ exchanger (NHE)
• Carbonic anhydrase bound to the apical membrane combines the secreted hydrogen with filtered carbonate to form carbon dioxide in the lumen
• The carbon dioxide then diffuses from the lumen into the tubule cell
• Within the cell carbon dioxides combines with water to form carbonic acid which dissociates to hydrogen and bicarbonate
• The bicarbonate can be transported out of the cell using the Na+ HCO3- symporter which put it into the interstitium

Question 22

What is the process for bicarbonate reabsorption and H+ excretion using amino acid metabolism?

Answer 22

• Glutamine in the proximal tubule cell is metabolized to alpha ketoglutarate and NH4+ (ammonium ion)
• Ammonium is transported into the lumen in exchange for sodium and is excreted
• Alpha ketoglutarate is further metabolized to form bicarbonate which is transported into the blood along with sodium

Question 23

What is acid base balance closely regulated by in the distal nephron?

Answer 23

Intercalated cells

Question 24

What type of cells are the target of aldosterones actions?

Answer 24

Principle cells

Question 25

What do intercalated cells have a high level of?

Answer 25

Carbonic anhydrase so they can rapidly convert carbon dioxide and water into hydrogen ions and bicarbonate

Question 26

What does the intercalated cells do to the H+ they produce?

Answer 26

They are pumped out of the cells by the hydrogen ATPase or the hydrogen potassium ATPase

Question 27

What does the intercalated cells use to move the bicarbonate they produce?

Answer 27

It enters the interstitium by the bicarbonate chloride antiporter

Question 28

What do Type A intercalated cells do during acidosis?

Answer 28

Secrete hydrogen ions and reabsorb bicarbonate

Question 29

What do type B intercalated cells do during alkalosis?

Answer 29

Secrete bicarbonate and reabsorb H+ ions

Question 30

What is different for how type A intercalated cells secrete H+ during acidosis vs the proximal tubule?

Answer 30

The apical hydrogen ATPase and hydrogen potassium ATPase is used rather than the sodium hydrogen antiporter

Question 31

How do type B intercalated cells reabsorb H+ during alkalosis?

Answer 31

They reabsorb hydrogen ions by transport into the interstitium on the basolateral side of the cell while bicarbonate is secreted into the lumen