EFFECT OF PLASMA BICARBONATE LEVEL ON PROXIMAL TUBULE SODIUM-REABSORPTION IN NH4-CL-LOADED DOGS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 87  (5) , 804-812
Abstract
To examine the effects of mild and severe chronic metabolic acidosis on proximal tubule sodium reabsorption, 6 dogs were given 10 mEq. Kg per day and 5 dogs were given 20mEq/kg per day of NH4Cl for 3 days and compared to 12 normal dogs during a steady-state water diuresis and following the i.v. administration of ethacrynic acid (EA) (2 mg/kg) utilizing standard clearance methodology. In the severely acidotic group (pH decrease > 0.2) plasma pH was 7.08 .+-. 0.06 and plasma bicarbonate was 6.3 .+-. 1.0 Eq/l compared to a pH of 7.33 .+-. 0.02 and bicarbonate of 13.4 .+-. 0.7 in mild acidosis (pH decrease < 0.2). During a steady-state water diuresis, urine flow was 14.2 .+-. 0.9 in the severely acidotic compared to 10.5 .+-. 0.7 ml/min per 100 ml glomerular rate (GFR) in normal dogs (P < 0.01). Following EA administration, Na clearance increased 38.4 .+-. 3.5 in severely acidotic dogs and 27.6 .+-. 2.0 ml/min per 100 ml GFR in normal dogs (P < 0.02). In mild acidosis, steady-state fractional urine flow and the increase in fractional Na clearance following EA were not significantly different than normal dogs. Chronic metabolic acidosis leads to an increase in distal solute load and an enhanced natriuretic effect of EA secondary to a decrease in proximal tubule Na reabsorption which may be dependent upon the degree of reduction in the plasma bicarbonate level.