Résumé
The salivary glands produce 1.5 l of fluid per day. As in other organs, the general paradigm in the salivary glands is that water movement occurs secondary to osmotic driving forces created by active salt transport. Therefore, high water permeability in salivary glands is expected to need a variety of aquaporin (AQP), a water channel. Although four AQPs have been known to reside in salivary glands, the precise location and roles of AQPs have been not well examined. This study is aimed to investigate the distribution of AQPs in 3 major salivary glands and their changes after cholinergic stimulation using immunohistochemical study in Sprague Dawley rats weighing 300 g under pentobarbital sodium anesthesia. AQP1 was localized in the endothelial cells of all salivary capillary vessels and the myoepithelial cells. AQP4 was demonstrated in the epithelium of the excretory ductal cells of all salivary glands. AQP5 and 8 were abundantly present in the basolateral membrane and apical membranes of the serous acini including intercellular secretory canaliculi, whereas AQP5 was weakly present in mucous acini. In addition, AQP5 was found in the epithelium of the intercalated and striated ducts. Upon stimulation of carbachol (10 micro gram/kg, I.P). AQP5 and 8 tended to translocate from basolateral membrane to the apical membrane, appearing as clusters of dots. These results suggest that AQP5 and 8 are the candidate molecules responsible for the water movement in salivary acinar cells.