Abstract
Epithelia separate apical and basal compartments, and movement of substances via the paracellular pathway is regulated by tight junctions. Claudins are major constituents of tight junctions and involved in the regulation of tight junction permeability. On the other hand, the osmolality in the extracellular environment fluctuates in association with life activity. However, effects of osmotic changes on the permeaibility of claudins are poorly understood. Therefore, we investigated the effects of osmotic changes on the paracellular transport in MDCK II cells. Interestingly, apical hyposmolality decreased cation selectivity in the paracellular pathway gradually with time, and the elimination of the osmotic gradient promptly restored the cation selectivity. Apical hyposmolality also induced bleb formation at cell-cell contacts and changed the shape of cell-cell contacts from a jagged pattern to a slightly linear pattern. In claudin-2 knockout MDCK II cells, the decrease of cation selectivity, the bleb formation, nor the changes in the shape of cell-cell contacts was observed under the apical hyposmolality. Our findings in this study indicate that osmotic gradient between apical and basal sides is involved in the acute regulation of the cation selective property of claudin-2 channels.
Highlights
In multicellular organisms, epithelia act as a barrier between the external and internal environment
Under the condition where NaCl concentration in the apical side was decreased by half and the osmolality was adjusted with sucrose (‘apical isosmotic’ condition), the value of permeability of Na+ (PNa) was much higher than PCl immediately after the replacement of the apical solution, and the values of PNa and PCl were almost constant during 120 min of incubation (Fig 1A)
These results indicate that apical hyposmolality induces a gradual decrease in PNa and an increase in PCl in Madin-Darby canine kidney (MDCK) II cells
Summary
Epithelia act as a barrier between the external and internal environment. There are two routes for the movement of substances across the epithelia: transcellular and paracellular pathways. The permeability of the paracellular pathway is regulated by tight junctions (TJs), which are one mode of the junctional complexes located in the most apical part of the complexes [1,2,3,4]. The osmolality in the extracellular environment fluctuates in association with life activity such as water intake. A large family of integral membrane proteins constituting TJ strands, are the major determinants of TJ permeability [6,7,8].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
