Lack of functionally active sweet taste receptors in the jejunum in vivo in the rat

Background: When studied in enterocyte-like cell lines (Caco-2 and RIE cells), agonists and antagonists of the sweet taste receptor (STR) augment and decrease glucose uptake, respectively. We hypothesize that exposure to STR agonists and antagonists in vivo will augment glucose absorption in the rat. Materials and methods: About 30-cm segments of jejunum in anesthetized rats were perfused with iso-osmolar solutions containing 10, 35, and 100 mM glucose solutions (n = 6 rats, each group) with and without the STR agonist 2 mM acesulfame potassium and the STR inhibitor 10 μM U-73122 (inhibitor of the phospholipase C pathway). Carrier-mediated absorption of glucose was calculated by using stereospecific and nonstereospecific ¹⁴C-d-glucose and ³H-l-glucose, respectively. Results: Addition of the STR agonist acesulfame potassium to the 10, 35, and 100 mM glucose solutions had no substantive effects on glucose absorption from 2.1 ± 0.2 to 2.0 ± 0.3, 5.8 ± 0.2 to 4.8 ± 0.2, and 15.5 ± 2.3 to 15.7 ± 2.7 μmoL/min/30-cm intestinal segment (P > 0.05), respectively. Addition of the STR inhibitor (U-73122) also had no effect on absorption in the 10, 35, and 100 mM solutions from 2.3 ± 0.1 to 2.1 ± 0.2, 7.7 ± 0.5 to 7.2 ± 0.5, and 15.7 ± 0.9 to 15.2 ± 1.1 μmoL/min/30-cm intestinal segment, respectively. Conclusions: Provision of glucose directly into rat jejunum does not augment glucose absorption via STR-mediated mechanisms within the jejunum in the rat. Our experiments show either no major role of STRs in mediating postprandial augmentation of glucose absorption or that proximal gastrointestinal tract stimulation of STR or other luminal factors may be required for absorption of glucose to be augmented by STR.