EFFECT OF ACETAZOLAMIDE ON SODIUM-REABSORPTION IN DILUTING SEGMENT IN MAN

  • 1 January 1976
    • journal article
    • research article
    • Vol. 87  (4) , 630-636
Abstract
The effects of extracellular volume expansion (ECVE) and acetazolamide (ACTZ) on Na transport in the diluting segment were studied in man. All studies were performed at the peak of sustained oral water diuresis (osmol < 75 mosmol/kg). Distal delivery was estimated by the rate of urine flow and distal Na reabsorption was approximated by the generation of free water. Free water clearance (CH2O) for given rates of distal delivery expressed as V[volume](range 10-35 ml/min) was significantly lower and the clearance of Na, higher in the ACTZ group as compared with subjects with ECVE. When CH2O was plotted against distal delivery expressed as CCl- clearance + CH2O, no difference was detected between ACTZ and ECVE studies. ACTZ may not have a direct inhibitory influence on the NaCl pump at the diluting site. The lowering of CH2O/V following ACTZ is due to the flooding of the diluting site with the poorly reabsorbable HCO3-. The proximal action of ACTZ, which initiates urinary HCO3 loss, results secondarily in an apparent interference with the diluting mechanism in man.