Histamine is one of the important mediators that causes a variety of allergic inflammatory responses in the airway. In the present study, to determine the effect of histamine on ion transport function across the airway mucosa, we measured transepithelial potential difference (PD) of rabbit tracheal mucosa under open-circuit conditionsin vivo. A high impedance voltmeter was used to measure PD between a fluid-filled and perfused recording bridge located on the airway surface and a reference bridge in the subcutaneous space. Addition of histamine to the perfusate produced a biphasic response of PD consisting of a rapid decrease within 15 sec and the subsequent plateau, which was followed by a sustained increase after 5 min of addition. Pretreatment of tracheal mucosa with the Na channel blocker amiloride greatly inhibited the early phase reduction of PD in response to histamine, but had no effect on the late phase elevation. On the other hand, pretreatment with the Cl channel blocker diphenylamine-2-carboxylate inhibited the late phase increase of PD completely.
These results indicate that early and late responses of PD are dependent on Na and Cl, respectivly, and suggest that histamine may inhibit Na absorption and stimulate Cl secretion in the airway mucosa.
