Effect of Acetazolamide on Renal Tubular Bicarbonate Reabsorption in Newborn Dogs

Abstract

SummaryBicarbonate titration curves were determined in 15 neonatal dogs, 5 to 30 days of age, under conditions of isovolemia and with the administration of various doses of acetazolamide to inhibit renal carbonic anhydrase. Under each experimental condition used, no TM for bicarbonate reabsorption could be found. With no acetazolamide, essentially all of the bicarbonate filtered was reabsorbed even at filtered loads of 50 μeq/ml g.f.r. Acetazolamide at a dose of 5 mg/kg inhibited less renal bicarbonate reabsorption than at doses of 50, 100, and 500 mg/kg but there was no difference among the latter three doses. At the higher acetazolamide dose levels, 5.3 μeq of bicarbonate was inhibited per ml g.f.r., amounting to only 12–24% of the total bicarbonate reabsorption (depending upon plasma bicarbonate levels) indicating that the major portion of the renal bicarbonate reabsorption in the neonatal dog is independent of the effects of carbonic anhydrase.