The effect of ion transport inhibitors on the bioelectric responses of guinea-pig tracheal-epithelium to hypertonic D-mannitol solution.
Johnston-RA; Van Scott-MR; Rengasamy-A; Fedan-JS
Am J Respir Crit Care Med 2001 Apr; 163(5)(2)(Suppl):A659
Elevation of serosal or mucosal tonicity induces the release of the non-nitric oxide, non-prostanoid epithelium-derived relaxing factor (EpDRF) from guinea-pig tracheal epithelium, which subsequently diffuses to the underlying airway smooth muscle to initiate relaxation. Hypertonicity-induced smooth muscle relaxation via EpDRF is preceeded by a depolarization of the transepithelial potential difference. This study sought to characterize further the ion channels and/or transporters involved in the response of guinea-pig tracheal epithelium to hypertonic solution by determining the effects of inhibitors on transepithelial short-circuit current (Isc) responses. Isc responses of tracheal segments were measured in vitro using a Ussing chamber. Methacholine (3x10^-7 M) was added to the serosal surface to mimic conditions used in previous studies of EpDRF. Hypertonic D-mannitol solution (120mOsm) added to the mucosal solution decreased the Isc. Pretreatment with amiloride (3x10^-5 M; mucosal), NPPB (10^-4 M; mucosal), or bumetanide (10^-5 M; serosal) inhibited 30 +/- 2%, 77 +/- 8% or 7 +/- 2% of the baseline Isc, respectively. Amiloride inhibited 30 +/- 10% of the Isc induced by D-mannitol. NPPB almost completely abolished the Isc induced by D-mannitol while bumenatide inhibited 34 +/- 9% of the Isc response. Iberiotoxin (10^-7 M; mucosal and serosal) had no apparent effect. Ouabain (10^-5 M serosal) itself caused a progressive reduction in Isc which prevented assessment of the response to D-mannitol. These results indicate that apical membrane Na* and CL- channels and the basolateral Na*-K*- 2CL- cotransporter mediate the epithelial response to elevated mucosal tonicity.
Oxides; Muscles; In-vitro-studies; Methacholines; Bioelectric-effects; Ion-transport; Laboratory-animals; Animals; Animal-studies
American Journal of Respiratory and Critical Care Medicine. Abstracts of the American Thoracic Society 2001 International Conference, May 18-23, 2001, San Francisco, California