Effect of Plasma CO2 Tension on Renal Tubular Reabsorption of Bicarbonate

Abstract

In dogs anesthetized with Na pentobarbital, plasma bicarbonate was elevated by the infusion of isotonic NaHCO3 and plasma CO2 tension was varied by controlled ventilation with air, or CO2 mixtures. The rate of renal tubular reabsorption of bicarbonate varied directly with extracellular CO2 tension over a wide range, but was not directly influenced by extracellular pH. The inhibition of carbonic anhydrase by Diamox (2-acetylamino-1,3,4-thiadiazole-5-sulfonamide) resulted in a decrease in bicarbonate reabsorption which could be overcome by increasing CO2 tension. The direction and magnitude of the observed responses indicate that bicarbonate reabsorption is entirely dependent on the exchange of H ion derived from carbonic acid in the tubule cell for the fixed base of filtered bicarbonate in the tubular urine.