Paracellular absorption of nutrients in bats is high during intestinal luminal perfusions

PRICE, E. R.; BRUN, A; FASULO, V.; KARASOV, W. H; CAVIEDES-VIDAL, E.

San Francisco

Congreso; SICB Annual Meeting; 2013

Water-soluble nutrients can be absorbed across enterocytes via protein-mediated transport, or paracellularly through the tight junctions between enterocytes. Previous in vivo measurements of bats that were orally dosed with carbohydrate probes have shown that bats absorb larger proportions of nutrients paracellularly than similarly-sized non-flying mammals. While this could indicate greater paracellular permeability of the intestinal epithelium, it could also be caused by longer retention time or slow gastric evacuation. We sought to determine if bat intestines are particularly permeable to nutrient-sized molecules. We performed in situ intestinal luminal perfusions on Tadarida brasiliensis and Myotis lucifugus. We cannulated the intestine and recirculated an isosmotic buffer containing 10-75 mM D-glucose, 10-75 mM proline, and two carbohydrate probes that are only absorbed paracellularly, 1 mM L-arabinose, and 1 mM lactulose, and radioisotope tracers for these molecules. Absorption of arabinose (MW 150) was nearly double that of lactulose (MW 342), demonstrating a similar molecular size sieving effect as has been seen previously for various species in vivo. At low molarity proline conditions, paracellular absorption (assessed by arabinose clearance) can account for at least 44% of total proline absorption. At 75 mM proline, paracellular absorption accounts for a majority of proline absorption. These data demonstrate that insectivorous bats rely heavily on paracellular absorption for the uptake of nutrients and confirms the high intestinal permeability suggested by whole-animal studies. Supported by NSF Award 1025886.