Abstracts
1998 Digestive Disease Week

#984

DIFFERENTIAL EXPRESSION OF LUMINAL NA+/H+ EXCHANGER ISOFORMS IN THE ILEUM FOLLOWING MASSIVE INTESTINAL RESECTION. CE Shin, M Soleimani*, H Amlal*, RA Falcone Jr, BW Warner. Division of Pediatric Surgery, Children's Hospital Medical Center and * Division of Nephrology, University of Cincinnati College of Medicine, Cincinnati OH.

Na+/H+Exchangers (NHE) are key transporters involved in the absorption of electroneutral NaCl along the GI tract. In a rodent diarrhea model of lactose ingestion, expression of two luminal isoforms (NHE-2 and NHE-3) were shown to be unchanged in the ileum. The aims of this study were to determine the expression pattern of the brush border NHE isoforms associated with the diarrhea induced by massive small bowel resection (SBR) and to determined the effect of epidermal growth factor (EGF) on this expression pattern. METHODS - Adult male ICR mice underwent either 50% proximal SBR or sham operation (bowel transection/reanastomosis) and then received either saline or EGF (50 µg/kg) by orogastric gavage. At 24 hr, the remaining ileum was isolated and levels of mRNA encoding NHE-2 and NHE-3 were quantitated by Phosphor Imager readings of the Northern blots. RESULTS - SBR induced a 2-fold increase in NHE-3 mRNA while EGF caused a similar expression pattern after sham-operation but had no further effect on NHE-3 expression after SBR (see graph). However, the NHE-2 mRNA remained unchanged in all four groups. CONCLUSION - Following SBR, the expression pattern for NHE-2 and NHE-3 is distinctive when compared with other known models of absorptive diarrhea. The increased expression of NHE-3 after SBR and/or EGF administration implies a common mechanism for augmented absorption of NaCl and water. NHE-3 may be the primary luminal transporter of water and electrolytes following SBR.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.