The sodium hydrogen exchanger (NHE) plays an important role in the absorption of NaCl, the regulation of intracellular pH and cell growth. These functions are compromised in the inflammatory bowel diseases. The objective of this study was to examine the expression of the NHE-1 isoform during colitis induced by acetic acid or trinitrobenzenesulfonic acid in Sprague-Dawley male rats. We also examined the effect of dexamethasone on the expression of NHE-1. Levels of mRNA were estimated using the reverse transcription-polymerase chain reaction and slot blot analysis, and levels of protein were estimated by enhanced chemiluminescence light Western blot analysis. The levels of the NHE-1 mRNA and protein in colonic mucosa increased as assessed at 1, 2, 5 and 7 days post-acetic acid administration and 7 days post-trinitrobenzenesulphonic acid administration in the rats. The levels of mRNA were not suppressed by dexamethasone treatment in either case. These findings demonstrate that colitis-induced expression of the NHE-1 mRNA and protein is independent of the way colitis is induced. Although factor(s) responsible for the induction remain to be identified, our findings showing similar changes in the NHE-2 and NHE-3 mRNA isoforms, together with the lack of their suppression by dexamethasone, suggest that cytokines and intracellular pH are secondary factors.