Histochemical study of normal and collapsed tracheas in dogs.

Tracheas from 15 toy breed dogs with normal tracheas and 6 dogs with collapsed tracheas were examined histologically and histochemically. Tracheal cartilage was analyzed for chondroitin sulfate by means of alcian blue (CEC method) and for calcium with alizarin red S. Cartilage arcs from dogs with collapsed tracheas had areas that were apparently hypocellular, and some had other areas that appeared like fibrocartilage or fibrous tissue. Histochemically, collapsed tracheal cartilage had less chondroitin sulfate and calcium than did normal tracheal cartilage. Cartilage arcs from the collapsed tracheas were not uniformly affected to the same degree, and parts of a given tracheal arc appeared normal, whereas other parts had an abnormal histologic appearance.