Abstract 309
Poster Session I, Saturday, 5/1 (poster 154)
The SGLT-1 is the major glucose transporter of the small intestine. However, if glucose is present at high concentrations, a paracellular route is probably also involved in the absorption of glucose. This study concerned the determination of the extent of glucose absorption by the SGLT-1 transporter in rat jejunum at weaning and at early maturity to discriminate the fraction of glucose absorption via the SGLT-1 transporter and the paracellular route. The method consisted of 3-hr perfusions under anesthesia with isotonic solutions containing 200 mM glucose and 50 mM NaCl, in the presence or absence of 1 mM phloridzin (PHL), an inhibitor of SGLT-1. In weanling rats [Wln] (30-40 g), PHL abolished glucose absorption (+PHL: -0.5 ± 1.9; -PHL: 15.9 ± 1.2 umol/min x g, P<0.05), while in the developmentally mature rats [Mat](100-120 g) PHL only halved glucose absorption (+PHL: 8.7 ± 1.1; -PHL: 16.9 ± 1.1 umol/min x g, P<0.05). Reduction of net water absorption by PHL was proportionally less in [Wln] than in [Mat] rats. In [Wln]: +PHL: 10.5 ± 5.5; -PHL: 22.3 ± 4.0 uL/min x g (P<0.05); in [Mat]: +PHL: 5.0 ± 3.0; -PHL: 14.4 ± 3.8 uL/min × g (P<0.05). Due to the relatively low Na concentration, there was no effect due to PHL on Na transport in either the [Wln] or [Mat] rats. The data suggest that [Wln] rats absorb glucose entirely via the SGLT-1 transporter, even at high glucose concentrations, while in [Mat] rats the paracellular route is operational under these conditions.
