Bicarbonate buffer

1. Dr Fathi 3/12/21
Describe the mechanism of
control of body pH by the renal
system
5 marks

2. Introduction
•Renal play important role and neutralize more acid
than both respiratory and chemical buffers
•It maintain the normal acid base balance by
reabsorption of HCO3- and excretion of H+

3. HCO3 reabsorption
•At the proximal collecting tubule
•Filtered HCO3- combined with
filtered H (by carbonic anhydrase)
to produce H20 and CO2 (lipid
soluble)
•In the PCT renal cell, it recombine
again to form HCO3- which
reabsorb through basolateral
membrane by Na+ HCO3- co
transport

4. H+ excretion
•At the late distal tubule and
collecting duct
•CO2 and H2O combined to form
carbonic acid which dissociated
to H+, HCO3-
•H+ will be excreted to lumen,
HCO3- will be absorbed
•

5. In high acidity condition
•Kidneys will conserve HCO3- : reabsorb all filtered
HCO3-
•Kidney will increase secretion of H+ and simultaneously
generate new HCO3-
•In alkaline condition, reverse of above will occur