Intestinal perfusion demonstrates high paracellular nutrient absorption in an insectivorous bat, Tadarida brasiliensis.

PRICE, EDWIN; BRUN ANTONIO; FASULO, VERÓNICA; KARASOV WH; CAVIEDES VIDAL, E

Salzburg

Encuentro; Annual Meeting of the Society for Experimental Biology; 2012

Society for Experimental Biology

Water-soluble nutrients can be absorbed transcellularly across enterocyte membranes via protein-mediated transport, or paracellularly through the tight junctions between enterocytes. Previous in vivomeasurements of bats that were orally dosed with passively-absorbed 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. To determine whether bat intestines are particularly permeable to nutrient-sized molecules, we performed in situ intestinal luminal perfusions on Tadarida brasiliensis. 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 at least 66% of proline absorption. These data demonstrate that Tadarida brasiliensisrelies 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.