Following massive small bowel resection (MSBR), the remnant small intestine adapts to restore Na absorptive function. The possibility that this occurs through increases in cellular Na absorptive capacity was examined by assessing the regional effects of 50% proximal MSBR on the function and expression of apical membrane Na-H exchangers (NHE), NHE2 and NHE3. Morphometric analysis confirmed adaptive changes consistent with villus hypertrophy, particularly immediately distal to the anastomosis. Villus epithelium prepared by light mucosal scrapings from two week post-resected (R) and -transected control rats (T) exhibited comparable brush border hydrolase activities, total cell protein per DNA, and villin expression, but increased basolateral Na, K-ATPase activity. Parallel increases of 2-3 fold in protein and mRNA abundance of NHE2 and NHE3 were observed only in ileal regions distal to the anastomosis of resected rats. Basolateral NHE1 expression was unchanged. After 80% resection, increases in NHE2 and NHE3 became evident in proximal colon. We conclude that increased enterocyte expression and function of apical membrane NHEs in regions distal to the anastomosis play a role in the adaptive process following MSBR. The increased luminal Na load to distal bowel regions following proximal resection may stimulate increases in apical membrane NHE gene transcription and protein expression.