Intestinal Na+/H+ exchanger activity is up-regulated by bowel resection in the weanling rat

A. I. Sacks, S. A. Acra, W. Dykes, D. B. Polk, J. A. Barnard, J. Pietsch, Fayez K. Ghishan

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Increased Na+/H+ exchanger activity is associated with cellular hyperplasia. Cellular hyperplasia is an adaptive response to small-intestinal resection. Therefore, we hypothesized that the small-intestinal Na+/H+ exchanger activity increases in response to small-intestinal resection. Twenty-one-d-old, male Sprague-Dawley rats were randomly divided to receive either a 70% small intestinal resection (n= 59), or a mid-small intestinal transection (n= 49). Seven d postoperatively, the animals were killed and the Na+/H+ exchanger activity of the intestinal remnants was studied by a well validated brush border membrane vesicle technique. The initial rate of Na+ uptake in the presence of an outwardly directed pH gradient and the Vmax of the amiloride-sensitive Na+ uptake were significantly increased (p< 0.01 and p < 0.001, respectively) in the resection as compared with the transection remnants and to a greater magnitude in the distal as compared with the proximal remnants. Km values were not significantly different. The amiloride-sensitive Na+ uptake in the setting of various intravesicular pH was significantly greater (p < 0.001) in the distal resection as compared with the distal transection remnants, with points of enhanced Na+/H+ exchanger activity of intravesicular pH 6.62 and 6.87, respectively. The presence and activation of the Na+/H+ exchanger’s internal modifier site was confirmed by demonstrating the effect of intravesicular pH on Na+ efflux. The present study demonstrates an up-regulation of intestinal Na+/H+ exchange activity in a small-bowel resection model in the weanling rat. This adaptive increase in Na+/ H+ exchange activity is secondary to an increase in the Vmax of the intestinal Na+/H+ exchanger and is associated with a shift in the sensitivity of its internal modifier site. This adaptive response may play a role in the cellular hyperplasia in small-bowel resection.

Original languageEnglish (US)
Pages (from-to)215-220
Number of pages6
JournalPediatric Research
Volume33
Issue number3
DOIs
StatePublished - Mar 1993

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

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