MORPHOLOGICAL EXAMINATION OF RABBIT NASAL-MUCOSA AFTER NASAL ADMINISTRATION OF DEGRADABLE STARCH MICROSPHERES

Degradable starch microspheres as a dry powder were administered nasally into the left nostril of rabbits, twice per day at 10 or 20 mg per dose. Lomudal(R) Nasal powder (10 mg) was used as a reference. The administrations were run for 2, 4 or 8 weeks. After termination of the experiment, the nasal mucosa was examined by using light microscopy and scanning electron microscopy. The nasal cavity was to a major extent lined by ciliated columnar epithelium. Squamous epithelium was seen on the conchae. A mild hyperplasia of the columnar epithelium on the nasal septum on the left, administered side could be observed in rabbits that had received spheres for 8 weeks. This finding was observed in both doses but was not seen in animals treated for 2 or 4 weeks. No signs of inflammation, erosions or squamous metaplasia were seen. The morphology of the cilia was normal. The results from this study indicate that starch microspheres can be considered to be biocompatible and do not induce serious histopathological changes in the nasal mucosa.