Electroaffinity in paracellular absorption of hydrophilic D-dipeptides by sparrow intestine

CHEDIACK, JUAN G.; CAVIEDES VIDAL, ENRIQUE; KARASOV, WILLIAM H.

JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY

Elsevier

Año: 2006 vol. 176 p. 303 - 309

0174-1578

We previously demonstrated size selectivity in the absorption of nonelectrolyte hydrosoluble probes in birds, presumably by the paracellular pathway. Our goal in this study was to determine the charge selectivity in the absorption of hydrosoluble D-dipeptides, because there have been no studies of the electroaffinity of this absorption pathway in birds. For this purpose isosmotic solutions with two hydrophilic D-dipeptides: serine-ly- sine (positive at pH 7.4) and serine-aspartic (negative at pH 7.4) were gavaged into the stomach in nonanesthe- tized house sparrows (Passer domesticus), and injected into the pectoralis with a syringe in different trials. Fractional absorption was calculated as F = [AUC by gavage)]/[AUC by injection] (AUC = area under the curve of plasma probe concentration vs. time). Frac- tional absorption was significantly higher for the posi- tively charged than negatively charged dipeptide (respectively, F=0.30±0.05 vs. F=0.17±0.03). These findings give the first evidence of cation selectivity by the paracellular route in the absorption of hydrosoluble solutes in the small intestine in birds.