Glucose and amino acid absorption in house sparrow intestine and its dietary modulation.
We acclimated house sparrows (Passer domesticus; 26 g) to high-starch (HS), high-protein (HP), and high-lipid (HL) diets and tested the predictions that uptake of D-glucose and amino acids will be increased with increased levels of dietary carbohydrate and protein, respectively. HS birds had lower mediated D-glucose uptake rate than HP birds. Total uptake of L-leucine at low concentration (0.01 mM), but not of L-proline at 50mM, was increased by dietary protein. Measures of D-glucose maximal mediated uptake (1.2 +/- 0.2 nmol.min-1.mg-1) and intestinal mass (1 g) indicated that the intestine's mediated uptake capacity was only approximately 10% of the D-glucose absorbed at the whole animal level. This implied that nonmediated glucose absorption predominated. We applied a pharmacokinetic technique to measure in vivo absorption of L-glucose, the stereoisomer that does not interact with the Na(+)-glucose cotransporter. At least 75% of L-glucose that was ingested was apparently absorbed. This adds to the increasing evidence that substantial passive glucose absorption occurs in birds and may explain why mediated D-glucose uptake does not increase on high-carbohydrate diets.
Caviedes-Vidal
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Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis, Argentina.
Karasov
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WH
D000596:Amino Acids / Q000493:pharmacokinetics*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001692:Biological Transport; D001717:Birds / Q000378:metabolism*; D004032:Diet; D005947:Glucose / Q000493:pharmacokinetics*; D007408:Intestinal Absorption
D000596:Amino Acids; D005947:Glucose