Micropipette measurement of airway submucosal gland secretion. Autonomic effects

We describe a micropipette method for obtaining secretions from single submucosal gland ducts in vivo in cat tracheas. The secretory rate of 65 glands sampled under basal conditions in 16 animals varied from 3 to 30 nl/min (mean +/- SE, 9.05 +/- 0.60 nl/min) and varied 2 to 3-fold among glands sampled within an animal. Sequential samples collected from individual ducts during a 10-min period were highly repeatable (correlation coefficient, 0.96) and were remarkably constant for as long as 4 h. Vagal cooling decreased the secretory rate by a mean of 39% (n = 11, p less than 0.05). Stimulation of the cervical vagus nerves increased flow from 8.3 +/- 0.7 to 16.4 +/- 0.8 nl/min (n = 15, p less than 0.01), an effect that was abolished by intravenous injection of 0.5 mg of atropine sulfate/kg of body weight or by cooling of the vagus nerves, but not by 0.08 mg of phentolamine/kg given intravenously. Intravenous injection of 0.3 mg of phenylephrine/kg of body weight increased flow from 8.6 +/- 0.6 to 18.9 +/- 1.1 nl/min (n = 20, p less than 0.001), an effect that was prevented by phentolamine, but not by atropine. We conclude that cholinergic and alpha-adrenergic stimulation increases fluid secretion from feline submucosal glands.