Ion transport processes and middle ear physiopathology. An experimental approach using cell culture.

The role of the middle ear (ME) epithelium is primarily to keep the cavities air-filled and fluid-free. This condition requires elimination of mucus and cellular debris from the tympanic cavity by the ciliary activity. This clearance activity may be related to active ion transport processes in the epithelium. This paper presents a review of the experimental data suggesting the existence of ion transports in ME, and demonstrating the contribution of the culture of ME epithelial cells to the investigation of ion transport properties. Primary cultures of ME epithelial cells from Mongolian gerbils (Meriones unguiculatus) were undertaken. Polarized monolayers exhibited domes on non-porous supports. On porous supports, the absorptive function was shown to be related to a Na+ absorption from apical to basal sides of the epithelium, by means of apical amiloride-sensitive Na+ channels and basolateral Na+, K(+)-ATPase. In turn, this sodium absorption would generate an osmotic gradient and drive a water flow. An amiloride-induced chloride transport is also suggested. A hormonal modulation of these ion transport properties might play a role in the development of the mucociliary impairment that initiates chronic otitis media. The establishment of a middle ea cell line using wild-type SV 40 infection is in progress. This might provide further information on the physiology of the ME.