Can the epithelium affect allergen-evoked histamine release from the perfused guinea pig trachea?

The aim of this study was to investigate the influence of the epithelium on allergen-evoked histamine release. Isolated tracheal preparations from guinea-pigs, with the epithelium either left intact or removed, were used. The trachea was perfused and challenged with egg-albumin (EA) either extra- or intraluminally. Fractions of the perfusate were collected for analysis of the histamine and EA contents. When EA was added intraluminally and the epithelium was removed, a marked peak in histamine release could be detected. In the presence of intact epithelium there was no marked histamine peak. EA added extraluminally gave the same results but the histamine peak was less pronounced. The epithelium apparently acts as a barrier, the nature of which remains to be elucidated.