The effects of ethanol on mucociliary clearance

Mucociliary clearance by the in vitro frog palate can be used as a model to study such clearance by mammalian lung. Frog palates bathed in Ringer's solution exhibited a constant mucociliary clearance rate for over 2 hr. When the bathing solution was exchanged for one containing ethanol, the mucociliary clearance rate was detectably inhibited by 300 mg/100 ml (mg%) ethanol and significantly inhibited by 400 (50%) and 500 mg% (67%) ethanol. At a concentration of 500 but not 200 mg%, ethanol significantly increased both the amount and the apparent viscosity of the frog palate mucus secreted in 1 hr. Mucus removed from palates bathed in Ringer's solution containing 500 mg% ethanol had no effect on the mucociliary clearance of palates bathed in Ringer's solution alone, and mucus from palates bathed in Ringer's solution alone failed to restore the mucociliary clearance of palates bathed in Ringer's solution containing 500 mg% ethanol. These results suggest that while mucus secretion and rheology are affected by ethanol, such changes in palate mucus do not account for the ethanol-induced inhibition of mucociliary clearance, but rather that the inhibition is the result of a ciliotoxic action of ethanol. Prior exposure of palates to histamine significantly attenuated the inhibitory effect of 500 mg% ethanol on mucociliary clearance, while 200 mg% ethanol significantly potentiated the inhibitory effect of dopamine. It is concluded that the neurohumoral environment of the ciliated epithelium in part determines the effect a given concentration of ethanol will have on mucociliary clearance.