Funaki H, Yamamoto T, Koyama Y, Kondo D, Yaoita E, Kawasaki K, Kobayashi H, Sawaguchi S, Abe H, Kihara I
Department of Pathology, Institute of Nephrology, Niigata 951-8510, Japan.
Am J Physiol. 1998 Oct;275(4):C1151-7. doi: 10.1152/ajpcell.1998.275.4.C1151.
Aquaporin (AQP) 5 gene was recently isolated from salivary gland and identified as a member of the AQP family. The mRNA expression and localization have been examined in several organs. The present study was focused on elucidation of AQP5 expression and localization in the eye, salivary gland, and lung in rat. RNase protection assay confirmed intense expression of AQP5 mRNA in these organs but negligible expression in other organs. To examine the mRNA expression sites in the eye, several portions were microdissected for total RNA isolation. AQP5 mRNA was enriched in cornea but not in other portions (retina, lens, iris/ciliary body, conjunctiva, or sclera). AQP5 was selectively localized on the surface of corneal epithelium in the eye by immunohistochemistry and immunoelectron microscopy using an affinity-purified anti-AQP5 antibody. AQP5 was also localized on apical membranes of acinar cells in the lacrimal gland and on the microvilli protruding into intracellular secretory canaliculi of the serous salivary gland. In the lung, apical membranes of type I pulmonary epithelial cells were also immunostained with the antibody. These findings suggest a role of AQP5 in water transport to prevent dehydration or to secrete watery products in these tissues.
水通道蛋白（AQP）5基因最近从唾液腺中分离出来，并被鉴定为水通道蛋白家族的一员。其mRNA表达和定位已在多个器官中进行了检测。本研究重点在于阐明大鼠眼睛、唾液腺和肺中AQP5的表达和定位。核糖核酸酶保护分析证实了AQP5 mRNA在这些器官中的强烈表达，但在其他器官中的表达可忽略不计。为了检测眼睛中mRNA的表达位点，对几个部分进行了显微切割以分离总RNA。AQP5 mRNA在角膜中富集，但在其他部分（视网膜、晶状体、虹膜/睫状体、结膜或巩膜）中未富集。使用亲和纯化的抗AQP5抗体，通过免疫组织化学和免疫电子显微镜技术发现，AQP5选择性地定位于眼睛角膜上皮的表面。AQP5也定位于泪腺腺泡细胞的顶膜以及伸入浆液性唾液腺细胞内分泌小管的微绒毛上。在肺中，I型肺上皮细胞的顶膜也被该抗体免疫染色。这些发现表明AQP5在这些组织中的水转运中发挥作用，以防止脱水或分泌水性产物。
