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Procainamide uptake by rabbit proximal tubules.
The Journal of Pharmacology and Experimental Therapeutics
|February 1, 1983
Summary
Procainamide secretion involves renal proximal tubule cells competing for uptake. Carbonic anhydrase inhibitors also reduce organic cation excretion by inhibiting this secretion process.
Area of Science:
- Pharmacology
- Nephrology
- Cell Physiology
Background:
- Procainamide is an organic cation actively secreted by renal proximal tubules.
- Understanding the mechanisms of procainamide secretion is crucial for drug efficacy and renal handling.
- Previous studies indicated transtubular secretion inhibition by various organic cations and carbonic anhydrase inhibitors.
Purpose of the Study:
- To investigate the mechanisms of [3H]procainamide uptake in renal proximal tubule cells.
- To determine the role of basolateral membrane uptake in organic cation secretion.
- To elucidate the effect of carbonic anhydrase inhibitors on organic cation transport.
Main Methods:
- Studying [3H]procainamide uptake in dissected S2 segments of superficial proximal tubule cells.
- Assessing the effects of hypothermia, non-radiolabeled procainamide, cimetidine, quinidine, acetazolamide, benzolamide, and ouabain on uptake.
- Utilizing previously established methods for isolated perfused proximal tubules.
Main Results:
- [3H]procainamide uptake was reduced by hypothermia and dose-dependently by other organic cations (procainamide, cimetidine, quinidine).
- Carbonic anhydrase inhibitors (acetazolamide, benzolamide) significantly reduced [3H]procainamide uptake.
- Ouabain did not affect [3H]procainamide uptake, suggesting Na+-K+-ATPase is not the sole driving force.
Conclusions:
- Organic cations compete for basolateral membrane uptake, contributing to their mutual reduction in tubular secretion.
- Acetazolamide and benzolamide inhibit proximal tubular secretion, thereby reducing organic cation urinary excretion.
- The basolateral membrane potential, influenced by Na+-K+-dependent adenosine triphosphatase, is not the exclusive driver for organic cation uptake into renal tubule cells.