Diurnal patterns in gene expression (mRNA protein) of the intestinal hexose transporters sodium glucose transporter 1 (SGLT1) and glucose transporters-2 and −5 (GLUT2 and GLUT5) are well-established in the rat duodenum and jejunum. In contrast, in ileum, mRNA but not protein expression varies diurnally. We hypothesized that diurnal expressions of intestinal hexose transporters are inducible in the ileum after massive proximal small bowel resection. Aim: To determine whether 70% jejunoileal resection can induce a diurnal rhythm in protein expression of hexose transporters. Methods: Diurnal expressions of mRNA (SGLT1, GLUT2, GLUT5) and protein (SGLT1) were studied in ileum of rats 1 and 8 wk after 70% mid-small bowel resection at four time points (3AM, 9AM, 3PM, and 9PM; n=6 rats at each time point; 24 rats were studied similarly at 1 wk after sham celiotomy with bowel manipulation only. Mucosal scrapings of rat ileum were obtained. RT-PCR was used to measure mRNA, and protein levels were determined by semi-quantitative Western blotting. Both RNA and protein levels are expressed as a ratio to the housekeeping gene GAPDH for standardization. Continuous data (weight) are x±SEM. Results: At 1 wk after 70% resection, rats lost 5±1% body weight but by 8 wk had gained 48±4% over preoperative weight. During the postoperative period, rats continued to eat primarily at night time (65% to 74% intake 6PM to 6AM). Our previous studies in normal rats showed that mRNA of SGLT1 peaked at 9PM (3.1 fold), but protein levels had no diurnal variation (Surgery, 2007). Similarly, this pattern persisted in sham-operated rats 1 wk postoperatively (p<0.03). In rats 1 wk after 70% jejunoileal resection, SGLT1 mRNA levels continued to demonstrate a diurnal rhythm with peak expression at 9PM in the remnant ileum (p<0.002); however, 70% resection was also associated with a diurnal rhythm of SGLT1 protein expression in the remnant ileum (peak expression at 9PM, p<0.03). The diurnal rhythms in RNA and protein expression disappeared in the remnant ileum 8 wk after resection (p≤0.08). mRNA for GLUT2 varied similarly to SGLT1, while mRNA for GLUT5 continued to cycle diurnally at both 1 and 8 wk postoperatively (p<0.003). Protein data for GLUT2 and GLUT5 are pending. Summary: Massive (70%) mid-small bowel resection induced a dirunal rhythm in SGLT1 protein expression in the remnant ileum that disappeared by 8 wk postoperatively. Conclusion: Ileum responds early on to the effects of extensive small bowel resection (? more intraluminal nutrients) by adopting a diurnal expression in SGLT1 protein via a post-translational process; chronic adaptation reverses this diurnal variation of SGLT1 gene and protein expression in the remnant ileum. Loss of diurnal variation after 8 wk suggests that other mechanisms, such as jejunal mucosal hyperplasia, are activated because of loss of absorptive surface to increase absorption proximally via intestinal adaptation.