Kidney Function V, Regulation of acid base status

Question 1

What is the optimum pH of blood
What is the [H+] in blood
What buffer controls blood pH

Answer 1

Generally 7.35-7.45,
35-45nM of free H+

CO2 + H2O <=> H2CO3 <=> HCO3- + H+

Question 2

What are the 4 methods of gaining acid

What are the 2 methods of losing acid

Answer 2

Gaining acid

• Metabolism of proteins/organic molecules
• CO2 prod from oxidative metabolism
• HCO3 loss in diarrhea
• Phosphoric acid prod in kidney

Loss of acid

• Used in anion metabolism
• H lost in vomit

Question 3

What 3 buffers are found in the blood

Answer 3

Bicarbonate
Haemoglobin
Plasma proteins

Question 4

What 2 buffers are found in ISS

Answer 4

Bicarbonate

Some protein

Question 5

What 3 buffers are found in cells

Answer 5

Intracellular proteins
Phosphate
Some bicarbonate

Question 6

What 2 buffers are found in urine

Answer 6

Phosphate

Ammonia

Question 7

How is pH controlled in the blood

What 2 structures control each

Answer 7

pH = [HCO3]/[pCO2]

Kidney controls HCO3
Lungs control pCO2

Question 8

Describe the 3 methods of renal acid base handling

• Bicarbonate reabsorption (PT, ALOH, ICA in CD)
• Acid excretion
• Adding more HCO3

Answer 8

Bicarbonate reabsorption

• Carbonic anhydrase => H + HCO3
• HCO3 => capillary
• H reassociates with HCO3 in filtrate => H2O CO2

Acid excretion
-Combines with HPO4 2- => H2PO4 - excreted

Adding more HCO3

• NaGlutamine/Glutamine FD => cell
• Broken down into NH4+ HCO3-
• NaNH4+ exchange => filtrate
• HCO3 => capillary

Question 9

Describe the 1 methods of respiratory acid base handling

-Alter pO2 via brainstem

Answer 9

Respiratory center in brainstem alters ventilation to retain/expel CO2

Question 10

Describe how respiratory acidosis arises

• buffer compensation
• respiratory compensation
• renal compensation

Answer 10

Acute/chronic alveolar hypoventilation (pCO2 retention)

Buffer
-Increased plasma [HCO3] => restore pH (pCO2 still high)

Respiratory
-N/A

Renal

• H secreted => HCO3 reabsorbed
• Increased glutamine prod in liver
• Both lead to increased HCO3

Question 11

Describe how metabolic acidosis arises

• buffer compensation
• respiratory compensation
• renal compensation

Answer 11

HCO3 loss
-HCO3 cannot be reabsorbed/secreted

H gain

• abnormal lipid metabolism
• protein metabolism

Buffer
-Decreased pCO2 by increased ventilation => remove excess H => restore pH

Respiratory
-Increased ventilation rate

Renal

• H secreted => HCO3 reabsorbed
• Increased glutamine prod in liver
• Both lead to increased HCO3

Question 12

Describe how respiratory alkalosis arises

• buffer compensation
• respiratory compensation
• renal compensation

Answer 12

Excess resp/hypoxic drive (pCO2 too low)

Buffer
-Decreased HCO3 reabsorbed => restore pH

Respiratory
-N/A

Renal
-Decreased H secreted => decreased HCO3 reabsorbed

Question 13

Describe how metabolic alkalosis arises

• Buffer compensation
• Respiratory compensation
• Renal compensation

Answer 13

H loss

• vomiting
• increased HATPase stimulation

HCO3 gain
-excess consumption

Buffer
-Increased pCO2 via hypoventilation => restore pH

Respiratory
-Decreased ventilation rate => hypoxia => hypoxic drive

Renal

• Decreased H secretion => decreased HCO3 reabsorbed
• Intercalated B cells => HCO3Cl excretion and HATPase reabsorption