Abstract
The aim of this study was to examine on the mechanisms of the water secretion in the submandibular glands acini of the normal and xerostomia. Male Wistar rats, weighing 250-280 g, were used. Experimental animals were divided into two groups, normal and xerostomia rats. Glycopyrrolate was administered to induce acute xerostomia, we raised both anti-AQP5 antibody and the anti-junctional proteins (ZO-1) antibody, and examined the localization of these proteins in rat submandibular gland acini. And permeability test of the tight junctions of acini were examined cytochemical, using HRP as a tracer. Salivary flow rate evoked by pirocarpine stimulation was decreased in xerostomia rats to about 50% of the normal rate. In the normal gland, the immunostaining for AQP5 was intense along the luminal membrane and was less intense on the basal membrane, and it was not detected on the lateral membrane in the acinar cells. ZO-1 was detected on the basolateral membrane. In the xerostomia rats, localization of AQP5 was decreased comparing with normal rats. And ZO-1 was disappeared in the essential portion. In the normal gland, tight junctions were impermeable to HRP indicating an adequate tight junction seal, but the tight junctions in the gland of xerostomia rats were permeable to it. Because the water-rich fluid is secreted in the lumen of the acinar cells where both AQP5 and tight junctions were abundantly present, it is reasonable to speculate that both intracellular and paracellular transport play an important role in the water secretion concomitantly. [J Physiol Sci. 2008;58 Suppl:S112]
