Sodium efflux from isolated submucosal gland in feline trachea

We examined Na efflux, as an indicator of electrolyte (or water) secretion from isolated feline tracheal submucosal glands. After incubation with 22NaCl-containing KRB solution (pH 7.4) at 37 degrees C, the 22Na-loaded glands were transferred to a superfusion apparatus in which perfusate was continuously pumped to the glands at a flow rate of 2.5 ml/min and sampled at 18-s intervals for 10-15 min. After 5 min of perfusion, a pharmacological or electrical field stimulation (FS) was given to the isolated glands. The instantaneous rate constant was calculated by measuring the radioactivity (counts/min) of each effluent sample. The mean rate constant of the base-line 22Na efflux was 0.21 min-1, which fell significantly to 0.03 min-1 after treatment with ouabain. Both methacholine and phenylephrine significantly accelerated the 22Na efflux to 3.6-fold and 1.8 times base-line efflux, respectively. FS produced a significant increase in the rate constant, and the increase was abolished by pretreatment with ouabain or tetrodotoxin. Further, atropine or phentolamine significantly suppressed the FS-evoked increase in the rate constant to 76 and 84%, respectively, of the maximal response evoked by FS alone. These results indicate that Na efflux from feline tracheal submucosal glands, which is dependent on ouabain-sensitive Na-K-ATPase activity in the secretory cells, is stimulated by both cholinergic and alpha-adrenergic agonists.