Adrenergic stimulation of Na+ transport across alveolar epithelial cells involves activation of apical Cl- channels |
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Authors: | Jiang, Xinpo Ingbar, David H. O'Grady, Scott M. |
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Abstract: | Alveolar epithelial cells were isolated from adultSprague-Dawley rats and grown to confluence on membrane filters. Mostof the basal short-circuit current(Isc; 60%) wasinhibited by amiloride (IC50 0.96 µM) or benzamil (IC50 0.5 µM).Basolateral addition of terbutaline (2 µM) produced a rapid decreasein Isc, followed by a slow recovery back to its initial amplitude. WhenCl was replaced withmethanesulfonic acid, the basalIsc was reduced and the response to terbutaline was inhibited. In permeabilized monolayer experiments, both terbutaline and amiloride produced sustained decreases in current. The current-voltage relationship of the terbutaline-sensitive current had a reversal potential of28 mV. Increasing Cl concentration in thebasolateral solution shifted the reversal potential to more depolarizedvoltages. These results were consistent with the existence of aterbutaline-activated Cl conductance in the apicalmembrane. Terbutaline did not increase the amiloride-sensitiveNa+ conductance. We conclude that -adrenergicstimulation of adult alveolar epithelial cells results in an increasein apical Cl permeability and thatamiloride-sensitive Na+ channels are not directly affectedby this stimulation. |
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