In vitro evaluation of nasal mucociliary clearance using excised rat nasal septum

Mucus on the nasal mucosa is translocated to the pharynx by ciliary beating, which is an important nonspecific defense mechanism called mucociliary clearance (MC). MC is one of the important factors determining the rate and extent of drug absorption after nasal application. The purpose of this study is to evaluate MC using rat nasal septum under physiological condition in an in vitro system. The nasal septum was excised from rats anesthetized with urethane and the movement of fluorescent microspheres (FMS) applied on the nasal septum was observed with a fluorescence microscope. FMS were transported at a constant velocity in the same direction for a few minutes, but addition of 4% mucin solution on the nasal septum maintained MC for at least 90 min after excision. With our evaluation system established by modifying the method of Saldiva, MC was determined to be around 1 mm/min. Furthermore, the ciliostatic effect of benzalkonium chloride was observed, and it was confirmed that β-adrenergic antagonists and a cholinergic antagonist decreased MC, and that β-adrenergic agonists and a cholinergic agonist tended to increase MC, indicating that our system is valid and useful for evaluating MC function and the effect of drugs and pharmaceutical additives for nasal application on MC.