Regulation of Acid-Base Balance Flashcards
Part of "Renal Regulation of Water and Acid-Base Balance" lecture
What is the role of kidneys in acid-base balance (3)?
- Secretion & excretion of H+
- Reabsorption of HCO3-
- Production of new HCO3-
What is the role of bicarbonate ions in acid-base regulation?
Act as a buffer
How can the Henderson-Hasselbalch equation be used to identify the cause of an alkalaemia / acidaemia?
What is an intercalated cell?
-
Secretes or absorbs acid / bicarbonate
- Regulation of blood pH
- Intercalated cells reabsorb K+ & HCO3-, while secreting H+ or vice versa
- This function reduces / increases the acidity of the plasma, and subsequently increases / decreases urine acidity; this mechanism is achieved by carbonic anhydrase activity
- Mitochondrial rich
What are the 2 types of intercalated cells?
- Alpha
- Beta
What is the function of the alpha intercalated cells?
- HCO3- reabsorption & H+ secretion

What is the function of beta intercalated cells?
- HCO3- secretion & H+ reabsorption

Outline the reabsorption of bicarbonate ion in PCT
Outline the reabsorption of bicarbonate ion in DCT & CD
How is bicarbonate transported into the interstitium through the basolateral surface?
- NBC-1 transporter

Outline the production of new bicarbonate in PCT.
Which amino acid within intercalated cells is used as a mediator for ammonia release?
- Glutamine

How is ammonia transported into the filtrate?
- NHE3 anti-porter

What happens to ammonia when in the filtrate?
- Ammonia is protonated by hydrogen ions in the filtrate to form ammonium ions
- The bicarbonate that dissociated from glutamine enters circulation

What does carbonic acid dissociate into?
- Bicarbonate and hydrogen ions

Which transporters secrete hydrogen ions into the tubular fluid?
- NHE2 transporters

Outline the production of new bicarbonate in DCT & CD.
Which ion behaves as a urinary buffer in the tubular fluid?
- Phosphate ions

Identify the acid-base disorder:
pH=7.2
HCO3-= 17 mEq/L
PCO2= 35 mmHg
Metabolic acidosis
Identify the acid-base disorder:
pH=7.5
HCO3-= 17 mEq/L
PCO2= 35 mmHg
Respiratory alkalosis
Ms L, a 25-year-old healthy woman on her holiday develops stomach infection with nausea and vomiting.
Following data was collected for her: Blood pH = 7.1, [HCO3-] = 16mEq/L, PCO2= 30mmHg.
Identify the compensatory mechanism being used by her body.
[Normal values: Blood pH=7.4, [HCO3-] = 24mEq/L, PCO2= 40mmHg]
Options:
1. Renal compensation – Reduced reabsorption of Bicarbonate ions
2. Renal compensation – Reduced excretion of ammonia and proton ions
3. Respiratory compensation – Hypoventilation
4. Respiratory compensation – Hyperventilation
Respiratory compensation – Hyperventilation
Ms S, a 25-year-old woman while trekking the Himalayas develops symptoms of dizziness and pain.
Following data was collected for her: Blood pH = 7.6, [HCO3-] = 16mEq/L, PCO2= 25mmHg.
Identify her acid-base disorder.
[Normal values: Blood pH=7.4, [HCO3-] = 24mEq/L, PCO2= 40mmHg]
- Metabolic alkalosis
- Respiratory alkalosis
- Metabolic acidosis
- Respiratory acidosis
Respiratory alkalosis
Ms J, a 25-year-old woman with a history of asthma, on her holiday develops stomach infection with diarrhoea.
Following data was collected for her: Blood pH = 7.1, [HCO3-] = 16mEq/L, PCO2= 45mmHg.
Identify her acid-base disorder.
[Normal values: Blood pH=7.4, [HCO3-] = 24mEq/L, PCO2= 40mmHg]
1. Metabolic acidosis
2. Respiratory acidosis
3. Mixed alkalosis
4. Mixed acidosis
Mixed acidosis