Renal compensation is the final mechanism for the reversal of pH change within t

In the proximal tubules, bicarbonate reabsorption is coupled to hydrogen secretion. Bicarbonate is moved out of the cell by Na+/K+ pumps, Na+/HCO3- cotransporters, and HCO3-/Cl- countertransporters located within the basolateral membrane, whereas hydrogen ions are secreted into the tubule filtrate by Na+/H+countertransporters and H+ pumps located in the apical membrane. Bicarbonate must first be converted to carbon dioxide by carbonic anhydrase in the tubule in order to move into the cell, where it is converted back to bicarbonate by the same enzyme. With the generation of bicarbonate, a hydrogen ion is produced that must be secreted by the mechanisms identified above. In the distal tubules, the secretion of hydrogen ions is coupled to the production of new bicarbonate ions. The basolateral membrane contains HCO3-/Cl- countertransporters and chloride channels that move bicarbonate out of the cell, coupled to the movement of chloride in. The chloride is then able to exit the cell via chloride channels. On the apical membrane, K+/H+countertransporters and H+ pumps are involved in the secretion of hydrogen ions. The movement of potassium into the cell is coupled to the outward movement of hydrogen, and the active hydrogen pumps move hydrogen out against the gradient. The generation of new bicarbonate occurs as a consequence of the metabolic activity of the cells of the tubular system of the kidneys. They use ATP for the Na+/K+ and H+ pumps. The carbon dioxide generated by metabolism is converted into HCO3- by carbonic anhydrase within the intercalated cells of the distal tubule. Finally, during severe acidosis, bicarbonate can be produced in the kidneys from glutamine in the cells of the proximal tubule.