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