BACKGROUND & AIMS: Active D-glucose absorption has been theorized to increase convective flow and enhance tight junction permeability such that paracellular transport becomes the major mechanism of D-glucose absorption. This concept was tested in rats by measuring the absorption of four gavaged, nonmetabolizable six-carbon sugars (L-glucose, L-galactose, L-mannose, and D-mannitol) thought to be absorbed solely by the paracellular route. METHODS: Uptake of gavaged probes was measured by recovery in 24-hour urine specimen collections. RESULTS: L-glucose (71.2% +/- 2.4%) absorption exceeded that of the other probes (1.4%-9%). Coadministration of 3.0 mol/L D-glucose, 0.22 mol/L D-glucose, or chow significantly reduced the absorption of L-glucose to 38.1% +/- 7.2%, 61% +/- 3.3%, and 53.6% +/- 3.5%, respectively, but did not influence the absorption of the other six-carbon probes. CONCLUSIONS: (1) L-glucose seems to have a weak affinity for a D-glucose carrier and is not a marker of paracellular transport, and (2) paracellular transport accounts for a minimal fraction of D-glucose uptake; this fraction is not enhanced by ingestion of D-glucose or chow.
BACKGROUND & AIMS: Active D-glucose absorption has been theorized to increase convective flow and enhance tight junction permeability such that paracellular transport becomes the major mechanism of D-glucose absorption. This concept was tested in rats by measuring the absorption of four gavaged, nonmetabolizable six-carbon sugars (L-glucose, L-galactose, L-mannose, and D-mannitol) thought to be absorbed solely by the paracellular route. METHODS: Uptake of gavaged probes was measured by recovery in 24-hour urine specimen collections. RESULTS:L-glucose (71.2% +/- 2.4%) absorption exceeded that of the other probes (1.4%-9%). Coadministration of 3.0 mol/L D-glucose, 0.22 mol/L D-glucose, or chow significantly reduced the absorption of L-glucose to 38.1% +/- 7.2%, 61% +/- 3.3%, and 53.6% +/- 3.5%, respectively, but did not influence the absorption of the other six-carbon probes. CONCLUSIONS: (1) L-glucose seems to have a weak affinity for a D-glucose carrier and is not a marker of paracellular transport, and (2) paracellular transport accounts for a minimal fraction of D-glucose uptake; this fraction is not enhanced by ingestion of D-glucose or chow.
Authors: Enrique Caviedes-Vidal; Todd J McWhorter; Shana R Lavin; Juan G Chediack; Christopher R Tracy; William H Karasov Journal: Proc Natl Acad Sci U S A Date: 2007-11-19 Impact factor: 11.205