Alveolar Epithelial Ion and Fluid Transport -Adrenoceptor-mediated control of apical membrane conductive properties in fetal distal lung epithelia

Collett, A., S. J. Ramminger, R. E. Olver, and S. M. Wilson. -Adrenoceptor-mediated control of apical membrane conductive properties in fetal distal lung epithelia. Am J Physiol Lung Cell Mol Physiol 282: L621–L630, 2002. First published October 26, 2001; 10.1152/ajplung.00142.2001.— Distal lung epithelial cells isolated from fetal rats were cultured (48 h) on permeable supports so that transepithelial ion transport could be quantified electrometrically. Unstimulated cells generated a short-circuit current (Isc) that was inhibited ( 80%) by apical amiloride. The current is thus due, predominantly, to the absorption of Na from the apical solution. Isoprenaline increased the amiloride-sensitive Isc about twofold. Experiments in which apical membrane Na currents were monitored in basolaterally permeabilized cells showed that this was accompanied by a rise in apical Na conductance (GNa ). Isoprenaline also increased apical Cl conductance (GCl ) by activating an anion channel species sensitive to glibenclamide but unaffected by 4,4 -diisothiocyanatostilbene-2,2 -disulfonic acid (DIDS). The isoprenaline-evoked changes in GNa and GCl could account for the changes in Isc observed in intact cells. Glibenclamide had no effect upon the isoprenaline-evoked stimulation of Isc or GNa demonstrating that the rise in GCl is not essential to the stimulation of Na transport.