Hypoxemia reflexly increases secretion from tracheal submucosal glands in dogs.

We anesthetized dogs, ventilated their lungs via the lower trachea, and exposed the epithelial surface of the upper trachea and coated it with powdered tantalum. Secretions from submucosal gland ducts formed elevations (hillocks) in the tantalum layer; we counted the number of hillocks that appeared in a 1.2-cm2 field. In 12 dogs, during normoxemia, 12 +/- 2 hillocks/cm2 formed in 90 s; during severe hypoxemia [fractional inspired O2 concentration (FIO2) = 0.05], 40 +/- 4 hillocks/cm2 formed in 90 s. Injections of sodium cyanide (25-75 micrograms) into the arterial supply to the carotid body also stimulated tracheal submucosal gland secretion. Secretory response to hypoxemia was suppressed by 1) section of both carotid sinus body nerves in six dogs and 2) section of both superior laryngeal nerves and vagus nerves in six other dogs. During mild hypoxemia (FIO2 = 0.10 or 0.15) tracheal submucosal gland secretion still increased. We conclude that hypoxemia increases secretion from submucosal glands in canine trachea by a carotid body chemoreflex.