| Abstract: | Aquaporin (AQP) 5 gene was recently isolated from salivary glandand identified as a member of the AQP family. The mRNAexpression and localization have been examined in several organs. Thepresent study was focused on elucidation of AQP5 expression andlocalization in the eye, salivary gland, and lung in rat. RNaseprotection assay confirmed intense expression of AQP5 mRNA in theseorgans but negligible expression in other organs. To examine the mRNA expression sites in the eye, several portions were microdissected fortotal RNA isolation. AQP5 mRNA was enriched in cornea but not in otherportions (retina, lens, iris/ciliary body, conjunctiva, or sclera).AQP5 was selectively localized on the surface of corneal epithelium inthe eye by immunohistochemistry and immunoelectron microscopy using anaffinity-purified anti-AQP5 antibody. AQP5 was also localized on apicalmembranes of acinar cells in the lacrimal gland and on the microvilliprotruding into intracellular secretory canaliculi of the seroussalivary gland. In the lung, apical membranes of type I pulmonaryepithelial cells were also immunostained with the antibody. Thesefindings suggest a role of AQP5 in water transport to preventdehydration or to secrete watery products in these tissues. |
