TUBULAR EFFECTS OF ACUTE METABOLIC-ACIDOSIS IN RAT

Abstract

Micropuncture and clearance studies were performed to evaluate the effects of acute NH4Cl-induced metabolic acidosis. Studies were performed in 4 groups of rats; controls, urea-saline, saline and NH4Cl. Acidosis (pH: 7.25 .+-. 0.02 SEM [Standard error of mean], HCO3- = 12.4 .+-. 0.7 meq/l was associated with increased fractional Na excretion, 9.13% .+-. 0.52 and Ca excretion, 1.32% .+-. 0.43, which was significantly greater than controls, 0.30% .+-. 0.07 and 0.30% .+-. 0.07; urea-saline, 0.54% .+-. 0.1 and 0.54% .+-. 0.13; saline, 0.71% .+-. 0.17 and 0.47% .+-. 0.99. In the proximal tubule fractional reabsorption was less with saline, 41.5 .+-. 1.7, than either urea-saline, 51.1 .+-. 1.3 or the NH4Cl-infused group, 46.9 .+-. 0.4. Natriuresis of acute NH4Cl loading was associated with but cannot be accounted for by inhibition of proximal tubular reabsorption. The mechanism of inhibition of transport at sites beyond the proximal tubule was not clear but it was not volume expansion or increased solute load due to urea excretion.