1. Buffer method: Chemicals that prevent the pH of a solution from changing are called buffers. Blood buffers are NaHCO3, Na2HPO4, KHCO3 etc. Nephron tubular cells reabsorb ions such as Na+, K+, HC3-, PO43- etc. from the glomerular filtrate into the blood. These ions participate in the formation of buffers in the blood and prevent changes in blood pH.
Na+ + HCO3- → NaHCO3
2Na+ + HPO43- → Na2HPO4
K+ + HCO3- → KHCO3
2. Ammonia method: When blood pH value (acidity) decreases, NH4+ is produced by the reaction of NH3 and hydrogen ion (H+) in plasma and renal tubule cells. This results in a decrease in the concentration of H+ ions in the plasma and a change in the pH value of the blood. Again, increasing alkalinity has the opposite reaction.
3. Iron exchange method: If the acid level increases in the blood, the concentration of ions increases. Meanwhile, a Na+ ion enters the blood in exchange for an H+ ion. This results in a decrease in the concentration of H+ ions in the plasma and a change in the pH value of the blood. Again, when the blood alkalinization level increases, the rate of exchange of H+ and Na+ ions between the blood and the glomerular filtrate decreases and the blood pH changes.