title: The tight junction proteins claudin-7 and -8 display a different subcellular localization at Henle's loops and collecting ducts of rabbit kidney.
abstract: BACKGROUND
  The tight junction (TJ) regulates the passage of ions and molecules through the paracellular pathway. In multicellular organisms, epithelial sheets function as a barrier between a variety of environments and the internal media. Therefore, TJs are required to control the passage of diverse molecules in different epithelia. The mammalian nephron constitutes a particularly relevant model of this diversity, since the paracellular transport in this organ is significantly different along the various tubular segments. Here, we have analysed the distribution of claudins-7 and -8 in Henle's loops and collecting ducts isolated from rabbit kidneys.
  
  
  METHODS
  Renal segments were manually isolated from newborn and adult rabbit kidneys and processed for immunofluorescence. The distribution of claudins-7 and -8 was studied by confocal microscopy.
  
  
  RESULTS
  The localization of claudins-7 and -8 along Henle's loops and collecting ducts is remarkably different. While claudin-8 displays a clear cell border distribution in Henle's segment, claudin-7 shows a non-specific cytosolic staining. Moreover, in the collecting ducts, claudin-8 localizes at the TJ region, while claudin-7 shows a basolateral staining. This pattern is present from the newborn stage. The distribution of claudins along the mammalian kidney has been found to vary in different mammalian species. Accordingly, in the rabbit, we have found the expression of claudin-8 at the descending and ascending thin limbs of Henle, a distribution that differs from that found in the mouse by others.
  
  
  CONCLUSIONS
  In the rabbit Henle's loop, claudin-8 is present at the cellular borders of the descending and ascending thin limbs, while claudin-7 displays no specific labelling. Instead, at the collecting duct, both claudins are present but exhibit a different subcellular distribution.
authors.affiliation: Department of Physiology, Biophysics and Neurosciences, Center for Research and Advanced Studies, Cinvestav, Ave. Instituto Politecnico Nacional 2508, Mexico, DF 07360, Mexico.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Gonzalez-Mariscal
authors.forename: Maria Del Carmen
authors.initials: Mdel C
authors.lastname: Namorado
authors.forename: Dolores
authors.initials: D
authors.lastname: Martin
authors.forename: Gerardo
authors.initials: G
authors.lastname: Sierra
authors.forename: Jose L
authors.initials: JL
authors.lastname: Reyes
mesh_terms: D000818:Animals; D057167:Claudins; D005455:Fluorescent Antibody Technique; D066298:In Vitro Techniques; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D008138:Loop of Henle / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D011817:Rabbits; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: C473255:CLDN7 protein, human; D057167:Claudins; D008565:Membrane Proteins; C502011:claudin 8