Molecular support for high paracellular absorption in the intestine of flying mammals

CAVIEDES VIDAL, ENRIQUE; BRUN ANTONIO; FERNÁNDEZ MARINONE GUIDO; GATICA-SOSA CP; PRICE, EDWIN; AMWEG, AYELEN; ORTEGA HUGO; KARASOV, WILLIAM H.

Boston

Congreso; 2013 Experimental Biology (FASEB); 2013

Flying mammals absorb water-soluble nutrients (e.g. glucose) at the intestine mainly by the paracellular route [across tight junctions (TJ) between adjacent enterocytes], while non-flying mammals mainly rely on the transcellular route (across cell membrane using transporter proteins). We predicted that insectivorous bats Tadarida brasiliensis, compared to Mus musculus, would show enhanced expression of CLDN-2 (CLDN=claudin) and OCLN (occludin) TJ proteins, which have been described as responsible for the permeability of polar water-soluble solutes. We assessed the level and spatial distribution of CLDN-2, -3, -5, ZO-1 and OCLN by immunohistochemistry along the villus axis in the proximal intestine. Immuno-specificity of the antibodies was checked by western blot. No differences were found for CLDN-3 and ZO-1 between species. We confirmed low expression of CLDN-2 in mice (Holmes et al. 2006, Gene Expr Patterns 6: 581-8; no signal detected in our preparations), but in bats the villus tips exhibited CLDN-2. OCLN was expressed along the entire villus axis but with a stronger signal for the bat than for mice, giving additional support to our prediction. A third difference was that CLDN-5 was strongly expressed along the villus in bats, whereas in mice its presence was not detected. Findings suggest potential molecular mechanism(s) underlying the observed higher paracellular absorption in bats compared to mice.