alteration of aquaporin mrna expression after small bowel resection in the rat residual ileum and colon background diarrhea occurring after small bowel resection gradually improves due to intestinal adaptation it is known that several water channels termed aquaporins aqp are expressed in the gastrointestinal tract and facilitate water transport however the changes of aqp after bowel resection remain unclear in the present paper the alterations in aqp mrna expression were investigated after a massive small bowel resection in the rat residual ileum and colonmethods the 6weekold male spraguedawley rats n 15 underwent an 80 distal small bowel resection the residual ileum and colon were dissected on postoperative day 1 3 5 or 7 n 3 on each day total rna was purified from each mucosa and the expressions of aqp and sodiumdependent glucose transporter sglt1 mrna were analyzed by northern blot the plasma vasoactive intestinal polypeptide vip concentrations on the preoperative day and postoperative day 1 were assayedresults in the residual small intestine the expression of aqp1 and aqp3 mrna increased significantly on postoperative day 1 the aqp7 mrna increased on postoperative day 3 but the aqp4 mrna did not change after the bowel resection the sglt1 mrna gradually decreased after the bowel resection in the colon the expression of aqp3 increased on postoperative day 1 and 7 but aqp4 mrna did not change after surgery the aqp8 mrna levels increased slightly on postoperative day 7 plasma vip concentration did not change between preoperative day and postoperative day 1conclusions these results indicate that several aqp except for aqp4 were upregulated after a massive small bowel resection and that aqp might play important roles during adaptation