Electrophysiological properties of AQP6 in mouse parotid acinar cells

Salivary gland acinar cells secrete large amounts of water and electrolytes, where aquaporins (AQPs) are thought to be involved in the secretion. In the present study, we investigated expression/localization of AQP6, and the anion transporting properties of AQP6 in mouse parotid acinar cells. RT-PCR, western blotting and immunohistochemical analyses revealed expression of AQP6 in acinar cells, localized in apical membrane. Voltage ramp from -100 mV to +100 mV at a holding potential of -60 mV elicited outwardly-rectifying currents, in the presence of extracellular Cl(-) channel blockers and intracellular solution with 150 mM Cs(+). These outward currents were increased when extracellular Cl(-) was replaced by Br(-), NO(3)(-), I(-), or SCN(-), accompanying a negative shift of reversal potentials. The outward current was enhanced by extracellular Hg(2+). These results were consistent with the biophysical properties of transfected AQP6 oocytes or HEK cells, which indicate that the AQP6 channel is functionally expressed in parotid acinar cells, and suggest that AQP6 contributes to secretion of anions in parotid acinar cells.