RENAL REABSORPTION OF BICARBONATE DURING ACUTE RESPIRATORY ALKALOSIS*

Abstract

Renal reabsorption of bicarbonate was studied during acute, sustained respiratory alkalosis while plasma bicarbonate concentration was progressively elevated from approximately 10 meq/l to final values ranging between 35 and 45 meq/1 With plasma CO2 tensions of approximately 20 mm Hg, reabsorption was depressed to an essentially constant rate averaging 1.9 meq/100 cc of glomerular filtrate. These data suggest that in acute respiratory alkalosis, as in the normal, CO2 tension directly determines a fixed limit for bicarbonate reabsorption. This pattern contrasts with that seen in acute respiratory acidosis and with partial inhibition of carbonic anhydrase, where reabsorption rises as a curvilinear function of plasma bicarbonate concentration.