Abstract
We investigated the effect of β-adrenoceptor stimulants on the canine tracheal ciliated cells. A mucosal specimen of the tracheal membranous wall was placed in a chamber containing Hanks' solution. Membrane potential was recorded by an intracellular microelectrode, and ciliary beating was measured by a photoelectrical technique. lsoproterenol and salbutamol in 10-7 to 10-4 M caused a concentration-dependent increase in both frequencies of ciliary beating and small electrical oscillatories were superimposed on the membrane potential. Theophylline also increased frequencies of both activities in doses of 10-5 M and above. Onset of action of theophylline was later than that of isoproterenol or salbutamol. All the above drugs only slightly depolarized the membrane potential, in concentrations of 10-4 M. Propranolol (10-7-10-4 M) alone had little effect on ciliary beating and electrical activity. However, the effects of isoproterenol and salbutamol were effectively antagonized by propranolol (10-5 M). Dibutyryl cyclic AMP (10-7-10-4 M) caused concentrationdependent increases in ciliary beating and electrical activity. These results suggest that potent bronchodilators such as β-stimulants and theophylline increase the activity of tracheal ciliated cells by stimulating the intracellular cyclic AMP system.
