The effects of carbon monoxide and hypoxic hypoxia on amine-containing cells in the tracheal epithelium of young rabbits.

Endogenously fluorescent, singly occurring amine-containing cells in tracheal epithelium were examined in 3-, 10-, and 28-day-old rabbits. These cells are pyramidal in shape with the apex projected toward the tracheal lumen. The cytoplasm exhibits a yellow fluorescence which is predominantly supranuclear. Occasional, infranuclear, fluorescent cytoplasmic processes project from the cells. The numbers of fluorescent cells per unit length of trachea increase with age. Acute exposure of 10-day-old rabbits to 13% O2 decreases the number of detectable fluorescent cells in the tracheal compared to controls exposed to room air. Similarly, exposure to 750 ppm carbon monoxide decreases the number of fluorescent epithelial cells appearing in tracheas of 10- and 28-day-old rabbits. These results suggest that the amine-containing epithelial cells of the trachea respond to tissue hypoxia and that decreased airway pO2 is not necessary to elicit a response.