Renal Acid-Base Regulation Kidneys help regulate blood ph by excreting H+ and reabsorbing HCO3 Most of the h+ secretion occurs across the walls of the pct in exchange for Nat Antiport mechanism Moves Nat and H+ in opposite directions. Normal urine normally is slightly acidic because the kidneys reabsorb almost all HCO3 and excrete h+ Returns blood pH back to normal range.Renal Acid-Base Regulation ◼ Kidneys help regulate blood pH by excreting H+ and reabsorbing HC03 - . ◼ Most of the H+ secretion occurs across the walls of the PCT in exchange for Na+ . ◼ Antiport mechanism. ◼ Moves Na+ and H+ in opposite directions. ◼ Normal urine normally is slightly acidic because the kidneys reabsorb almost all HC03 - and excrete H+ . ◼ Returns blood pH back to normal range