1.5.1 Regulation of Acid-Base

Question 1

What ion channel is utilized in urine acidification?

Answer 1

H-Na exchanger on the apical surface

Question 2

Describe how ammonium is produced and excreted in the renal tubules? What is ion channel is used if ammonium is produced within the cells?

Answer 2

NH4-Na exchanger

Question 3

What are the important ion channels involved in bicarbonate reabsorption in the distal and collecting tubule? What type of cell is used for bicarbonate reabsorption?

Answer 3

H-K exchanger on the apical suface

HCO3-Cl exchanger on basal surface

Bicarbonate reabsorption occurs in the alpha intercalated cells of the distal/collecting tubule

Question 4

What are the three renal mechanisms involved in pH regulation?

Answer 4

1. Bicarbonate reabsorption - H secretion
2. Urine acidification (H titration using bicarb, H titration using phosphate)
3. Ammonium production

Question 5

What is the normal value for H2CO3? The ratio between HCO3 and H2CO3?

Answer 5

H2CO3 = 1.2 mEq/L

Ratio = 20

Question 6

What are some of the causes of metabolic alkalosis?

Answer 6

Generated by loss of H+ or gain of HCO3 (vomiting, diuretic therapy (thiazides), ingestion of anti-acids)

Maintenanace by renal HCO3 retention

Question 7

What the three indices of renal acid-base regulatory efficiency?

Answer 7

1. Net acid excretion
2. Urine anion gap
3. Plasma anion gap

Question 8

What are some of the causes of metabolic acidosis?

Answer 8

Gain of acid (endogenous H prod, exogenous H intake, renal H excretion)

Loss of HCO3 (decreased HCO3 reabsorption, increased HCO3 GI loss)

Question 9

What is the calculation for urine anion gap? Meaning of values

Answer 9

UAG = (Na + K) - Cl

Normal NH4 production, UAG is negative

Low NH4 production, UAG is zero or positive

Question 10

What are the normal values for pH, HCO3, PCO2?

Answer 10

pH = 7.4

HCO3 = 24 mEq/L

PCO2 = 40 mm Hg

Question 11

Describe how the kidneys will try to compensate for respiratory acidosis?

Answer 11

Question 12

What is the calculation for plasma anion gap? Normal values?

Answer 12

Plasma anion gap = Na - (Cl + HCO3)

Normal range: 8-16

Increases when blood pH is reduced

Question 13

Describe how the kidneys will try to compensate for respiratory alkalosis?

Answer 13

Question 14

What are the two buffers of urine acidification? (This is the reason that the pH of urine doesn’t ever drop below 4)

Answer 14

Phosphate and Bicarbonate

Question 15

What are some of the factors regulating H+ secretion and their corresponding mechanism?

Answer 15

Question 16

What are three conditions that will result in metabolic alkalosis with low NaCl (saline resistant)?

Answer 16

Hyperaldosteronism

Gitelman’s syndrome

Barterr’s syndrome

Question 17

What is different about beta intercalated cells? What are they used for?

Answer 17

The ion channels are inverted (the apical and basal polarities are flipped). The allows for bicarbonate secretion

Question 18

What are the two important renal locations for bicarbonate reabsorption?

Answer 18

Proximal tubule and distal/collecting tubule

Question 19

What type of acid is expelled by the lungs? kidneys?

Answer 19

Lungs: Volatile

Kidneys: Nonvolatile

Question 20

What ion channels are involved in bicarbonate reabsorption in the proximal tubule.

Answer 20

H-Na exchanger on the apical surface

HCO3 and Na cotransporter on the basal surface