Paracellular and total glucose absorption increase with age in nestling House sparrows

BRZEK, P.; CAVIEDES-VIDAL, E.; KARASOV, W. H.

BOSTON, MASSACHUSETTS

Congreso; Society for Integrative Comparative and Biology; 2009

Society Abstract

Diet digestive efficiency has been found to increase with age in nestling birds. Age-specific changes in activity of digestive enzymes have been shown, however, nothing is known about developmental changes in capacity for absorption of products of digestion. We studied for the first time developmental changes in glucose absorption in an altricial bird, House sparrow (Passer domesticus). Nestlings on days 3, 6, and 12 post-hatch were either fed or injected intramuscularly with radiolabeled L-glucose (absorbed only passively across intestinal tight junctions - paracellular transport), and 3-O-methyl-D-glucose (3-OMD-glucose, absorbed both actively and passively). We applied a pharmacokinetic method to estimate the proportion of glucose that was absorbed by fed nestlings (fractional absorption, FA). FA was lowest in youngest nestlings (0.70 for L-glucose, 0.79 for 3-OMD-gluocose) and increased significantly to essentially unity in oldest nestlings. The values in 6- and 12-d old birds were similar to those found previously in adult House sparrows. We conclude that the paracellular absorption pathway is relevant during ontogeny accounting for the majority of the water-soluble absorption in the intestine, and its magnitude increases with age. Supported by NSF IOS-0615678 to W.H.K.