Passive absorption of D-mannitol and L-arabinose in Passer domesticus.

CAVIEDES-VIDAL, E.; JUAN GABRIEL CHEDIACK; PESTCHANKER, M.; KARASOV, W.

Denver, Colorado

Congreso; Annual Meeting of the Society for Integrative and Comparative Biology; 2000

Society for Integrative and Comparative Biology

Passive absorption of D-mannitol and L-arabinose in Passer domesticus. E. Caviedes Vidal; J.G. Chediack; W.H. Karasov and M. Pestchanker. Previous studies found large amounts of radiolabel in plasma of several avian species fed H3L-glucose (the steroisomer thought to be absorbed passively and not actively). We tested the hypothesis that this reflects a substantial pathway for absorption of water soluble solutes. We gavaged solutions with different concentrations of either L-arabinose or D-mannitol into the stomach, took blood samples at different time-intervals from a wing vein, measured plasma concentration by gas chromatography, and calculated sugar extraction efficiency using a pharmacokinetic model. We found for both carbohydrates linear relationships between absorption and the sugar concentration of the gavaged solutions, indicating that absorption of D-mannitol and L-arabinose is passive. Extraction efficiency of D-mannitol was 54 to 64%, and 52 to 55% for L-arabinose. Results such as these cast doubt on prior estimates of intestinal absorptive capacity that have been used in evolutionary physiology analyses, and rise new questions about the possible exposure of animals to water soluble toxins that previously were thought to be relatively nonabsorbable. Supported by UNSL-grant to EC-V and NSF IBN 9723793 to WHK.