Factors Determining Carbon Dioxide Tension in Urine

Abstract

The relationship between urinary phosphate buffer excretion and CO2 tension of urine was investigated in female mongrel dogs under conditions of threshold and of elevated plasma bicarbonate concentration. In either circumstance, urinary pCO2 remained essentially constant and carbonic acid excretion increased only slightly, in the face of increases in phosphate excretion greater than 100 fold. Partial inhibition of renal carbonic anhydrase resulted in significant elevation in urinary pCO2 despite continuing minimal urinary phosphate concentration and excretion. The data are discussed in terms of the 2 hypotheses proposed to account for the elevated CO2 tension of alkaline urine. They are consonant with the hypothesis which relates this elevation to delayed dehydration of carbonic acid in the lumina of the renal tubules.