Antigenic challenge via the airway alters the permeability of the trachea in sensitized rats.

Inbred rats were sensitized by intraperitoneal injection of DNP19 ovalbumin (DNP-OA) or saline. The rats were subsequently challenged by exposure to an aerosol of DNP-OA or bovine gamma globulins (BGG) for 10 min. Tracheal tissue was processed immediately after challenge in fixative containing 1% lanthanum. Planimetry of transmission electron micrographs showed 59% of the intraepithelial membranes were stained with lanthanum in the DNP-OA-sensitized and DNP-OA-challenged group; 39% in the saline-sensitized, DNP-OA-challenged group, and 26% in the DNP-OA-sensitized, BGG-challenged group. X-ray static probe microanalysis confirmed that most lanthanum penetrated in the DNP-OA-sensitized and DNP-OA-challenged group. In this group, the magnitude of the mechanical response, measured by body plethysmography, correlated directly (r = 0.74) with the lanthanum penetration. Our results confirm that increased permeability of the intercellular spaces occurs in immediate pulmonary hypersensitivity. They suggest that this change in permeability may be involved in producing the mechanical response.