Distribution and size of mucous glands in the ferret tracheobronchial tree.

A transgenic ferret model of cystic fibrosis has recently been generated. It is probable that malfunction of airway mucous glands contributes significantly to the airway pathology of this disease. The usefulness of the ferret model may therefore depend in part on how closely the airway glands of ferrets resemble those of humans. Here, we show that in the ferret trachea glands are commonest in its most ventral aspect and disappear about half way up the lateral walls; they are virtually absent from the dorsal membranous portion. Further, the aggregate volume of glands per unit mucosal surface declines progressively by about 60% between the larynx and the carina. The average frequency of glands openings for the ferret trachea as a whole is only about one-fifth that in humans (where gland openings are found at approximately the same frequency throughout the trachea). Glands in the ferret trachea are on average about one-third the size of those in the human. Therefore, the aggregate volume of tracheal glands (per unit mucosal surface area) in the ferret is only about 6% that in humans. As in other mammalian species, airway glands in the ferret disappear at an airway internal diameter of ∼1 mm, corresponding approximately in this species to airway generation 6.