AUDITORY EPITHELIAL MIGRATION .2. MORPHOLOGICAL EVIDENCE FOR AUDITORYEPIDERMAL-CELL MIGRATION IN RAT

Morphology of the tympanic membrane (TM) and external auditory canal ( EAC) was studied in healthy, intact rat ears, TM-perforated ears (3 da ys after making the perforation) and TM-perforation-healed ears (14, 2 8 and 42 days after making the perforation). In intact ears, the epide rmis in the annular region of the EAC displayed a characteristic appea rance with cytoplasmic protrusions. We termed these protrusions as ''f inger-like projections''. Ln contrast to the rat, the annular region o f the EAC in the guinea-pig did not show ''finger-like projections''. Following a perforation in the centre of the anterior or the posterior quadrant of the pars tensa in rats the ''finger-like projections'' di sappeared from the annular region on the perforated side of the EAC, w hile the projections remained on the malleus side of the perforation e dge. In perforation-healed ears analysed 42 days after the perforation , the ''finger-like projections'' had recurred in the annular region o n the perforated side of the EAC. The ''finger-like projections'' are likely to express maturation (keratinization) and desquamation of epid ermal cells in the pars tensa and also could constitute morphological evidence of their migration on the TM.