AJP - Renal Physiology, Vol 252, Issue 2 322-F330, Copyright © 1987 by American Physiological Society
Total CO2 flux in isolated collecting tubules during carbonic anhydrase inhibition
M. E. Laski
These studies evaluated the effects of sodium transport inhibitors on total
CO2 flux (JtCO2) in the rabbit cortical collecting tubule after inhibition
of carbonic anhydrase. When ouabain was added to tubules during carbonic
anhydrase inhibition, reabsorptive JtCO2 rose and potential difference (PD)
decreased. Amiloride added to perfusate after carbonic anhydrase inhibition
decreased PD and did not alter JtCO2. If ouabain was added to an
ethoxyzolamide-treated tubule with amiloride present in perfusate, no
effects were detectable. Amiloride added to the bath of
ethoxyzolamide-treated tubules in high concentration (10-3 M), decreased
potential and increased JtCO2. If amiloride was added to the bath of
cortical collecting tubules from fasted rabbits, JtCO2 rose. This response
was not seen in cortical tubules from fed animals or in medullary
collecting tubules. These data demonstrate the existence of carbonic
anhydrase-independent acidification in this segment in vitro. The data from
studies with amiloride in the presence of intact carbonic anhydrase are
consistent with action on a basolateral sodium-proton exchange mechanism. A
cellular model that postulates a basolateral sodium-proton exchanger in an
acidifying cell is offered.
