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Evidence for a DCCD-sensitive component of proximal bicarbonate reabsorption
The American Journal of Physiology
|November 1, 1985
Summary
Active H+ secretion significantly contributes to proximal tubule bicarbonate absorption. Inhibitors like DCCD and amiloride revealed active transport mechanisms beyond passive Na+-H+ exchange, involving H+-ATPase or redox-driven pumps.
Area of Science:
- Nephrology
- Renal Physiology
- Cellular Biology
Background:
- Proximal tubule bicarbonate (HCO3-) absorption is crucial for acid-base balance.
- The role of active H+ secretion in this process remains incompletely understood.
Purpose of the Study:
- To investigate the contribution of active H+ secretion via brush border enzymes to proximal tubule HCO3- absorption.
- To differentiate between passive and active transport mechanisms.
Main Methods:
- Paired reperfusion of surface proximal convoluted tubules.
- Utilized inhibitors: dicyclohexylcarbodiimide (DCCD), amiloride, and acetazolamide.
- Manipulated bicarbonate and CO2 levels in perfusion solutions.
Main Results:
- DCCD inhibited CO2 absorption by 15-30%, indicating active transport.
- Amiloride inhibited CO2 absorption by 15% and disproportionately reduced fluid absorption.
- Combined DCCD with amiloride or acetazolamide showed significant inhibition of CO2 absorption.
Conclusions:
- Active H+ secretion, mediated by H+-ATPase or redox-driven H+ pumps, significantly contributes to proximal tubule HCO3- absorption.
- This active transport complements passive Na+-H+ exchange.