Absorption of 51Cr EDTA across the human nasal airway barriers in the presence of topical histamine.

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Abstract
Whether histamine, a mediator that causes exudation, affects the airway absorption of luminal solutes has been examined in a study of eight healthy volunteers. Fluid containing the absorption tracer chromium-51 labelled EDTA was instilled into one nasal cavity for 15 minutes, with a nasal pool-device (total volume 14 ml). The airway absorption of 51Cr EDTA determined by urinary recovery of radioactivity corresponded to 0.095 (SE 0.023) ml of the instillate in the absence of histamine. When histamine was added to the nasal instillate at a concentration of 2.0 mg/ml, which is known to produce substantial exudation of plasma into the airway lumen, the absorption of 51Cr EDTA was unchanged (0.093 (0.025) ml of the instillate). Separate experiments excluded the possibility that any swallowed portion of 51Cr EDTA could have contributed significantly to the amount absorbed. The present data agree with previous observations in guinea pig tracheobronchial airways, where histamine and other exudative agents did not increase the mucosal absorption of solutes from the airway lumen. These data suggest that the potent protein systems of blood plasma can transverse the endothelial-epithelial linings and operate on the surface of the airway mucosa without compromising its integrity as a barrier to luminal material.