Expression and localization of aquaporins, members of the water channel family, during development of the rat submandibular gland

Abstract

The expression and localization of aquaporins (AQP1-AQP5), members of the water channel family, in the developing rat submandibular gland were analysed using RT-PCR, Northern blotting and immunohistochemistry to explore their relation to the development of this salivary gland. RT-PCR analysis revealed unique expression patterns of each AQP. AQP1 was expressed constitutively during prenatal development, whereas the expression of AQP5 became more intense in the course of development from embryonic day 16.5 (E16) to E20. These expression patterns concurred with the results of Northern blot analysis. AQP3 and AQP4 mRNAs in the prenatal development were not detected in Northern blots, although they were detected by RT-PCR. During postnatal development, AQP5 and AQP1 mRNAs were expressed continuously, but no message for AQP3 or AQP4 was detected. AQP2 mRNA was not detected during either prenatal or postnatal development in this tissue. Immunohistochemical studies revealed that AQP5 was first localized at the apical membrane of proacinar cells at E18, and then became clearly distributed at the apical membrane of acinar cells in accordance with the differentiation and establishment of the mature acini. In addition, some vasculature also showed immunoreactivity for AQP5. AQP1 was immunolocalized in the blood vessels, including capillaries, of the gland throughout development. These observations suggest the existence of transcriptional regulation of rat AQP5, which is one of the most probable regulators of saliva production and secretion, during the establishment of the functional submandibular salivary gland.

Localization of Aquaporin Water Channels in the Airway of the Musk Shrew (Suncus murinus) and the Rat

“…A recent report showed that in human tissues AQP1 was detected only in the capillary endothelium of the lung and bronchus, and not in nasal mucosa [38]. While there is variation among animals, AQP1 is expressed in the capillary endothelial cells in various tissues [1,2,4,27,37,38,52,[56][57][58], and these observations may support our result. Immunoblotting of AQP1 showed bands of larger molecular weight corresponding to the glycosylated AQP1 [39] in both animals, but smaller bands were observed in the musk shrew than in the rat.…”

An Immunohistochemistry-Based Study on Aquaporin (AQP)-1, 3, 4, 5 and 8 in the Parotid Glands, Submandibular Glands and Sublingual Glands of Sj^|^ouml;gren^|^rsquo;s Syndrome Mouse Models Chronically Administered Cevimeline

“…To date, 13 types of AQPs have been confirmed (AQP-0 to AQP-12). It has been suggested so far that AQP-1, 3, 4, 5 and 8 exist in the salivary glands of humans and rodents [10][11][12]. It has been reported that AQP-5 is largely involved in water transport during saliva secretion in the salivary glands [13,14].…”

Effect of Cevimeline on Radiation-Induced Salivary Gland Dysfunction and AQP5 in Submandibular Gland in Mice

“…Aquaporins (AQPs) are membrane proteins forming water channels, and are widely distributed through the organisms. Of the known AQPs, AQP1, AQP3, AQP4, AQP5 and AQP8 have been identified in mammalian salivary glands 1,13,19) . In muscarinic agonist stimulation studies, Ma et al 15) found that showed no defect in the volume or composition of saliva in AQP1-and AQP4-knockout mice, but did in AQP5-knockout mice.…”

“…These reports have played an important role in the understanding of AQP5 in saliva flow 13,15,19) . One study investigated the distribution of AQP3, but the mechanism of this distribution remains to be elucidated 1) . For example, they demonstrated that high epithelial cell membrane water permeability is required for active, near-isosmolar fluid transport.…”