Yasuko Ishikawa and Hajime Ishida
Department of Pharmacology, Tokushima University School of Dentistry, 3-18-15 Kuramoto-cho, Tokushima 770-8504, Japan
Abstract: Water secretion from salivary glands, which are innervated by parasympathetic and sympathetic nerves, occurs in response to the stimulation by neurotransmitters. In general, parasympathetic or sympathetic stimulation produces a high flow of saliva as a result of the activation of M3 muscarinic or a1-adrenergic receptors, respectively. The secretory mechanisms of fluid secretion were osmotically regulated in response to a transepithelial ion gradient generated by ion transport systems that were located in the apical or basolateral membranes of the acinar cells. Recently, the identification of water-specific channels, or aquaporins (AQPs), in many mammalian tissue and cell types has provided insight into the molecular basis of water movement across biological membranes. It has been reported that several AQPs are expressed in salivary glands and especially AQP5 plays an important role in fluid secretion. This review will focus on the role of AQP5 in the movement of water across the apical plasma membrane in relation to the physiology and pathophysiology of salivary glands.
Keywords: Aquaporin-5, Salivary secretion, Neurotransmitter, Calcium mobilization, Cytoskeleton