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

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

Congreso; Experimental Biology 2014; 2014

Flying mammals absorb watersoluble nutrients (e.g. glucose) at the intestine mainly by the paracellular route [across tight junctions (TJ) between adjacent enterocytes], while nonflying 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 CLDN2 (CLDN=claudin) and OCLN (occludin) TJ proteins, which have been described as responsible for the permeability of polar watersoluble solutes. We assessed the level and spatial distribution of CLDN2, 3, 5, ZO1 and OCLN by immunohistochemistry along the villus axis in the proximal intestine.  Immunospecificity of the antibodies was checked by western blot. No differences were found for CLDN3 and ZO1 between species. We confirmed low expression of CLDN2 in mice (Holmes et al. 2006, Gene Expr Patterns 6: 5818; no signal detected in our preparations), but in bats the villus tips exhibited CLDN2. 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 CLDN5 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.