THE RELATION OF URINARY CO2 TENSION TO BICARBONATE EXCRETION*

Abstract

During maximal H2O diuresis, HCO3 excretion was elevated by the administration of either NaHCO3 or acetazolamide. In both instances urine CO2 tensions were 20 to 30 mm Hg higher than CO2 tensions of blood. There was no difference between the effects of NaHCO3 and acetazolamide on urine pCO2. Alterations in buffer excretion could not account for the high urine PCO2 following acetazolamide. The secretion of H+ by the distal tubule into HCO3-containing tubular fluid with delayed dehydration of H2CO3 affords the best explanation for the high urine CO2 tensions under these conditions. It is concluded that acetazolamide specifically blocks H secretion in the proximal tubule without affecting the distal tubule.