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 ca vities air-filled and fluid-free. This condition requires elimination of mucus and cellular debris from the tympanic cavity by the ciliary a ctivity. This clearance activity may be related to active ion transpor t processes in the epithelium. This paper presents a review of the exp erimental data suggesting the existence of ion transports in ME, and d emonstrating 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 support s. 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 g radient and drive a water flow. An amiloride-induced chloride transpor t is also suggested. A hormonal modulation of these ion transport prop erties might play a role in the development of the mucociliary impairm ent that initiates chronic otitis media. The establishment of a middle ear cell line using wild-type SV 40 infection is in progress. This mi ght provide further information on the physiology of the ME.