Comparison of intestinal passive absorption of L-arabinose among two species: pigeons (Columba livia) and rats (Wistar).

FASULO, V.; JUAN GABRIEL CHEDIACK; CAVIEDES-VIDAL, E.; KARASOV, W.

Riberao Preto

Congreso; XXI Congresso da Associação Latino Americana de Ciências Fisiológicas; 2003

Associação Latino Americana de Ciências Fisiológicas

Comparison of intestinal passive absorption of L-arabinose among two species: pigeons (Columbia livia) and rats (wistar). Fasulo, Verónica1, Chediack, Juan1 Karasov, William2 and Caviedes-Vidal, Enrique1. 1Departamento Bioquímica y Ciencias Biológicas. Universidad Nacional de San Luis. Argentina. 2Department of Wildlife Ecology. University of Wisconsin, Madison. USA. E-mail: jchedi@unsl.edu.ar   Recently we demonstrated that intestinal absorption of substances by the small intestine in birds occurs vastly through the paracellular pathway. However, the magnitude of this mechanism in other taxa is still being discussed. In contrast to our findings in avian species, studies in rats reported that the paracellular absorption is small or even negligible even though nominal intestinal areas of birds are smaller than in  mammals (e.g. pigeons: 85-103 cm2; rats: 100-142cm2). Objective: Our goal in this study was to test if the observed difference is due to different experimental designs. Consequently, to generalize our previous findings we performed experiments using identical methodology comparing L-arabinose kinetics and apparent extraction efficiency (F) between Common pigeons (Columba livia) and similar sized rats (Wistar). Methods: In chronic intraduodenal catheterized 14 hs fasted rats (body mass=240-300g; n=6) and pigeons (body mass=276-295g; n=6) we administered isosmotic solutions of L-arabinose, by intraduodenal and intramuscular way, in different trials. Serial blood samples were taken between 0 and 240 min. The amount of L-arabinose absorbed or bioavailability (F) was calculated from areas under the post-absorption and post-injection plasma curves (AUC) with a classical pharmacokinetics equation F=[AUC by gavage]/[ AUC by injection]. Using the Kedem-Katchalski equation we analyzed the difference between species to assess the contribution of convective and diffusive flux in each case. Results: L-arabinose bioavailability in pigeons and rats were: 0.42 ± 0.15 vs. 0.15 ± 0.01; P < 0.01. This represents that in pigeons paracellular absorption is more than twice than in rats. Data obtained from the Kedem-Katchalski equation permit to infer that these differences seem mainly attributable to differences in paracellular solvent flux and to a minor extension to differences in effective paracellular pore size. Conclusion: These findings suggest that passive absorption may vary among taxa, independently of body size and nominal intestinal area (cm2). Supported by FONCYT (01-03101), CyT-UNSL (9502) to EC-V and NSF (IBN-0216709) to WHK.