Regulation of the paracellular Na+ and Cl- conductances by the NaCl-generated osmotic gradient in a manner dependent on the direction of osmotic gradients.
In the present study, we investigated the effect of osmolality on the paracellular ion conductance (Gp) composed of the Na(+) conductance (G(Na)) and the Cl(-) conductance (G(Cl)). An osmotic gradient generated by NaCl with relatively apical hypertonicity (NaCl-absorption-direction) induced a large increase in the G(Na) associated with a small increase in the G(Cl), whereas an osmotic gradient generated by NaCl with relatively basolateral hypertonicity (NaCl-secretion-direction) induced small increases in the G(Na) and the G(Cl). These increases in the Gp caused by NaCl-generated osmotic gradients were diminished by the application of sucrose canceling the NaCl-generated osmotic gradient. The osmotic gradient generated by apical [corrected] application of sucrose without any NaCl gradients had little effects on the Gp. However, this apical [corrected] application of sucrose produced a precondition drastically quickening the time course of the action of the NaCl-generated osmotic gradient on the Gp. Further, we found that application of the basolateral hypotonicity generated by reduction of NaCl concentration shifted the localization of claudin-1 to the apical from the lateral [corrected] side. These results indicate that the osmotic gradient regulates the paracellular ion conductive pathway of tight junctions via a mechanism dependent on the direction of NaCl gradients associated with a shift of claudin-1 localization to the apical side in renal A6 epithelial cells.
Tokuda
Shinsaku
S
Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
Niisato
Naomi
N
Nakajima
Ken-Ichi
K
Marunaka
Yoshinori
Y
D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002713:Chlorine / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005246:Feedback / Q000187:drug effects / Q000502:physiology; D007668:Kidney / Q000502:physiology*; D009997:Osmotic Pressure / Q000187:drug effects; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000008:administration & dosage*; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*; D014982:Xenopus laevis
D012965:Sodium Chloride; D002713:Chlorine; D012964:Sodium