Expression of the aquaporin 8 water channel in a rat salivary epithelial cell.
Aquaporins are a family of water channels considered to play an important role in fluid transport across plasma membranes. Among the reported isoforms, relatively little is known about the functional role of aquaporin 8 (AQP8), and there are no cell lines known to express the AQP8 protein. We report here that the rat submandibular epithelial cell line, SMIE, expresses AQP8. Using RT-PCR, the presence of mRNA for AQP8 was demonstrated in these cells. Confocal immunofluorescence experiments revealed that the AQP8 protein is primarily present in the apical membranes of SMIE cells. When grown as a polarized monolayer on collagen coated polycarbonate filters, and exposed on their apical surface to different hyperosmotic (440, 540, or 640 mOsm) solutions, net fluid movement across SMIE cells was 8-25-fold that seen under isosmotic conditions. Similarly, when grown on coverslips and then exposed to a hypertonic solution, SMIE cells shrunk as a function of time. Together, these results suggest that SMIE cells endogenously express functional AQP8 water channels.
Hoque
A T M Shamsul
AT
Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA.
Yamano
Seiichi
S
Liu
Xibao
X
Swaim
William D
WD
Goldsmith
Corinne M
CM
Delporte
Christine
C
Baum
Bruce J
BJ
D000818:Animals; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001826:Body Fluids / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006982:Hypertonic Solutions / Q000494:pharmacology; D007473:Ion Channels; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014018:Tissue Distribution
D020346:Aquaporins; D006982:Hypertonic Solutions; D007473:Ion Channels; D012333:RNA, Messenger; C108330:aquaporin 8