The effect of ambroxol on ion transport in isolated tracheal wall was studied by the electrophysiological (Ussing) method. It was shown that ambroxol influenced one component of the transepithelial electrical potential difference (PD), which is related to ion transport processes mechanically stimulated by a jet of bathing fluid from a peristaltic pump. The other component of the PD, which represented stable ion transport processes, was not influenced by the drug. The stimulation-dependent component of the PD was deeply inhibited, or sometimes even eliminated, by a change in the pH of the stimulating bathing fluid from 7.4 to 6.4. Ambroxol, in a concentration of 5 microM, restored the mechanical reactivity of tissue stimulated by jet of fluid at pH 6.4. We put forward the hypothesis that ambroxol influences the ion transport processes, which are evoked by stimulation of "cough receptors", in a way that probably augments airway cough clearance.

Ambroxol↗

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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.

Ambroxol↗