RESUMO
This study was aimed to comprehend the pattern of renal response in bicarbonate reabsorption during various alterations in acid-base equilibrium in twelve dogs. In metabolic acidosis induced by infusion of hydrochloric acid, as the plasma bicarbonate and filtered load of bicarbonate decreased eminently, urinary excretion of bicarbonate was found to be negligible. which was attributable to almost complete reabsorption via the hydration of CO2. In metabolic alkalosis induced by infusion of sodium bicarbonate, along with an increment of plasma concentration of bicarbonate, all filtered bicarbonate was reabsorbed, with negligible amount of excretion until the plasma level attains the renal bicarbonate threshold. During the respiratory acidosis and alkalosis with higher or lower arterial Pco2, the bicarbonate reabsorption varied linearly with plasma Pco2. The linear relationship indicated that the hydration of CO, was an important source of hydrogen ion for the reabsorption of bicarbonate. In this regards, however, in metabolic alkalosis the renal bicarbonate threshold was found to be much higher than that of respiratory acidosis. The characteristics of renal bicarbonate reabsorption, during the mixed acid-base disturbances of metabolic and respiratory origin with no considerable alteration of plasma pH, induced by hydrochloric acid infusion with hyperventilation or sodium bicarbonate infusion with CO2 inhalation, were quite similar to those in metabolic acidosis and alkalosis caused by simple hydrochloric acid or sodium bicarbonate infusion, respectively.