Renal Na-Reabsorption and O2-Uptake in Dogs During Hypoxia and Hydrochlorothiazide Infusion

Abstract

In anesthetized dogs renal O2 consumption and Na reabsorption were determined during hypoxia and under the influence of hydrochlorothiazide. In hypoxia (arterial O2 saturation 35%) less Na is reabsorbed and renal O2 consumption is diminished. Urine volume is increased with a decrease in U/Posm (urine/plasma osmolar ratio) U/Pcreat (urine/plasma creatinine ratio) and TcH2O (volume of solute free water reabsorbed). During administration of hydrochlorothiazide both Na reabsorption and O2 consumption are lowered. Urine volume and Cosm [osmolar clearance] are elevated, U/Posm and U/Pcreat decreased while TcH2O remains unchanged. Plotting Na reabsorption ([mu]eg/g min) against O2 consumption ([mu]mol/g min) results in a straight line which intercepts the O2 consumption axis at 1 [mu]mol/g min. We believe that this value may be equated with renal basal O2 consumption, i.e., without Na reabsorption. The O2 requirement for renal Na reabsorption is calculated to be 28.6-32 [mu]eg Na/[mu]mol O2.