Acid base balance

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.