Effects of expectorants on the canine tracheal ciliated cells

Many expectorants are clinically effective as they reduce viscosity and facilitate expectoration. There are, however, few reports on effects of expectorants on tracheal ciliated cells. We investigated the effects of N-acetylcysteine, ethylcysteine and bromhexine on the ciliary activities of the canine trachea. Ciliary movement was estimated using a phototransistor, and intracellular electrical activity was measured with a microelectrode method, in vitro. N-Acetylcysteine, ethylcysteine and bromhexine in low concentrations under a low perfusion rate (0.1 ml/min) produced an increase in the amplitude and frequency of ciliary beating, while N-acetylcysteine and ethylcysteine caused a cilio-depression in high concentration. N-Acetylcysteine, ethylcysteine and bromhexine, under a low perfusion rate, did not affect the intracellular electrical activity. On the other hand, these three drugs under a high perfusion rate (1 ml/min) produced no change in the ciliary movement and the intracellular electrical activity in concentrations of 10(-8)-10(-4) M. These results suggest that the increase in ciliary activity produced by the mucolytic drugs is not due to a direct effect on the ciliated cells, but rather to a mucolytic effect on the mucus around the cilia.