Inhibition of the sodium/hydrogen antiport by ammonium ion.

Abstract

Previous work from our laboratory suggests that one mechanism of ammonium transport across the intestinal membrane may be substitution of ammonium for sodium in the sodium/hydrogen antiport. This study further supports this mechanism by demonstrating an inhibitory role for ammonium in the sodium/hydrogen exchange. Whole 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. Ammonium is an inhibitor of sodium in the sodium/hydrogen exchanger. Quantitatively, the inhibition appears to be competitive. The inhibitory effect of ammonium on sodium/hydrogen exchange supports a mechanism of ionized ammonium transport where it substitutes for sodium in the sodium/ hydrogen exchanger. This is a mechanism by which hyperchloremic metabolic acidosis occurs following urinary intestinal diversion.