Electrophysiological investigation of the effects of ambroxol on the transepithelial Na+ ion transport pathway in airways.

Isolated tracheal wall was studied by the Ussing method during selective inhibition of single, electrogenic, transepithelial ion transport pathways with either amiloride (for Na+) or bumetanide (for Cl-). It was shown that ambroxol influences the Na+ transepithelial transport pathway which is partly responsible for the hyperpolarization after mechanical stimulation of the mucosal surface of tracheal wall. Ambroxol augments the Na+ current during the presence of bumetanide in the experimental system, but diminishes it during the washing of amiloride from the measuring chamber. These bidirectional effects of ambroxol provide indirect evidence that the drug is a partial agonist for the memberance receptors which form part of the intrawall control system responsible for integration of airwall function with the transepithelial ion transport.