Sugar absorption in bats. Are they mammals or birds?.

CAVIEDES-VIDAL, E.; JUAN GABRIEL CHEDIACK; CRUZ NETO, A. P.; KARASOV, W.

Beijing

Congreso; The XIXth International Congress of Zoology; 2004

China Zoological society - Chinese Academy of Sciences

SUGAR ABSORPTION IN BATS. ARE THEY MAMMALS OR BIRDS?   Enrique Caviedes-Vidal1, Juan G. Chediack1, Ariovaldo Pereira Cruz-Neto2 and William H. Karasov3   1Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis, Chacabuco 917. 5700 San Luis, Argentina; ecv@unsl.edu.ar 2Departamento de Zoologia. Universidade Estadual Paulista, Av. 24A 1515. 13506-900 Rio Claro, SP, Brasil; 3Department of Wildlife Ecology, University of Wisconsin-Madison, 1630 Linden Dr., Madison WI 53706, USA.   We are engaged in a research program to evaluate the extent and significance of paracellular absorption of water-soluble compounds (e.g. D-glucose) by the small intestine in species across different animal taxa. One emerging pattern is that in mammals studied to date, the contribution of this mechanism to the total absorption of glucose (15 ? 25%) is lower than observed in birds (50 ? 80%). Because it has been observed that birds, relative to mammals of a given size, have greater energetic requirements but smaller small intestine surface areas, perhaps  they rely more on the paracellular route to absorb water soluble nutrients to meet their nutritional requirements. This would be consistent with a functional strategy of flying animals to diminish the mass load represented by larger intestines, and hence the cost of locomotion activity. To test this prediction we measured the absorption of sugars (L-rhamnose, absorbed paracellularly) in a flying mammal, the frugivore bat, Artibeus literatus. In addition, we measured the small intestine nominal surface area of these bats. Five animals were captured at the campus of the Universidade Estadual Paulista in Rio Claro (Brasil) and kept with food and water ad libitum. L-rhamnose was gavaged into the stomach dissolved in a 300 mosm solution. The carbohydrate was also injected into the pectorals to estimate probe elimination constant. After injection or gavage serial blood samples were collected from the wing and leg veins into heparinized capillary tubes. The concentration of sugar in plasma was determined using HPLC with fluorescence detector. Typical pharmacokinetic procedure was used to estimate the fractional absorption of the sugar by the bats, thus the amount of  L-rhamnose absorbed was calculated from area under the post-absorption and post-injection plasma curves (AUC: area under the probe concentration vs. time curve). Fraction absorption (F), also called bioavailability, was calculated as F = [AUC/dose (gavage)] / [AUC/dose (injection)]. The obtained value was F= 70.5 ± 1.7 % (mean ± 1 SEM, N=5). The nominal intestinal surface area measured for three animals (body mass=69.58±4.69g) was 27.2 ± 3 cm2. Obtained data support this first test for a functional convergence in water-soluble absorption strategy. Results beg for additional testing. Supported by FONCYT (01-03101), UNSL CyT 9502 to EC-V, NSF IBN-0216709 to WHK.