Acetylcholine acts on M3 muscarinic receptors and induces the translocation of aquaporin5 water channel via cytosolic Ca2+ elevation in rat parotid glands.

To evaluate the role of aquaporin5 (AQP5) in salivary secretion induced by cholinergic stimulation, the alteration of the distribution of AQP5 in rat parotid tissues induced by acetylcholine (ACh) was studied by immunobolt analysis. The treatment of the tissues with ACh within 1 min induced the translocation of AQP5 from intracellular membranes (ICM) to apical membranes (APM), but that for more than 5 min resulted in the converse translocation from APM to ICM. The ACh-induced increase in the amount of AQP5 in APM was inhibited by atropine, p-F-HHSiD and TMB-8, but not by methoctramine, staurosporine or H-7. The calcium ionophore A-23187 alone stimulated the translocation of AQP5 between APM and ICM. These results indicated that ACh acted on M3 muscarinic receptors and induced the translocation of AQP5 between ICM and APM, and that the cytosolic Ca2+ elevation by ACh may play a key role in this translocation in rat parotid glands.