INHIBITION OF THE SODIUM HYDROGEN ANTIPORT BY AMMONIUM ION/

Purpose: Previous work from our laboratory suggests that one mechanism of ammonium transport across the intestinal membrane may be substitut ion of ammonium for sodium in the sodium/hydrogen antiport. This study further supports this mechanism by demonstrating an inhibitory role f or ammonium in the sodium/hydrogen exchange. Materials and Methods: Wh ole brush border intestinal enterocytes were studied, incorporating a fluorescent marker for sodium transport. The kinetics of the effect of ammonium on sodium transport were determined. Results: Ammonium is an inhibitor of sodium in the sodium/hydrogen exchanger. Quantitatively, the inhibition appears to be competitive. Conclusions: The inhibitory effect of ammonium on sodium/hydrogen exchange supports a mechanism o f ionized ammonium transport where it substitutes for sodium in the so dium/hydrogen exchanger. This is a mechanism by which hyperchloremic m etabolic acidosis occurs following urinary intestinal diversion.