Proximal convoluted tubule
- Acid base starts in proximal convoluted tubule of nephrons
- 70% of HCO3– reabsorb in PCT
- In glomerulus, H+,HCO3– get easily filtered in glomerular filtrate
- In lumen, H+ and HCO3– combine to form H2CO3
- Carbonic anhydrate present near wall convert carbonic acid into carbon dioxide and water inside tubular wall
- This CO2 and H2O dissociate into H+ and HCO3– by carbonic anhydrase
- HCO3– get exchanged with chloride , into the blood and get absorbed
- Now, H+ in cell exchanged with freely filtered Na+. So, Na+ enter cell and H+ get into lumen( excreted through urine)
Distal convoluted tubule (academia condition)
- Contain two types of intercalated cells i.e. A cells and B cells
- A cells- secrets protons to urine in exchange for Na, K and retain bicarbonate.
- B cells- opposite i.e. secrets bicarbonate and reabsorbs protein.