Uptake of iron aerosols by mouse airway epithelium.

Spontaneously breathing mice were exposed to an aerosol of iron oxide for 3 hours. Participation of the tracheal and bronchial epithelium in the uptake of iron oxide was noted immediately following the exposure and at 1 day, 4 days, and 7 days postexposure. Observations with the electron microscope revealed that iron oxide was pinocytosed and converted to ferritin and hemosiderin in all epithelial cell types except mucous cells. Iron content increased over time and approximately 50% of the nonmucous cells contained hemosiderin by 4 days postexposure. Ferritin and hemosiderin, but not iron oxide, were noted in connective tissue cells in the submucosa beneath the airway epithelium. Soluble iron and/or ferritin produced in the airway epithelial layer was transported to the submucosa, but normal epithelium prevented the penetration of deposited iron oxide particles to the connective tissue compartment.