The tight junction proteins claudin-7 and -8 display a different subcellular localization at Henle's loops and collecting ducts of rabbit kidney.
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.
Gonzalez-Mariscal
Lorenza
L
Department of Physiology, Biophysics and Neurosciences, Center for Research and Advanced Studies, Cinvestav, Ave. Instituto Politecnico Nacional 2508, Mexico, DF 07360, Mexico.
Namorado
Maria Del Carmen
Mdel C
Martin
Dolores
D
Sierra
Gerardo
G
Reyes
Jose L
JL
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
C473255:CLDN7 protein, human; D057167:Claudins; D008565:Membrane Proteins; C502011:claudin 8