EFFECT OF EPIDERMAL GROWTH-FACTOR AND DEXAMETHASONE ON EXPLOSIVE DEAFNESS

Objective To study the expression of epidermal growth factor receptor (EGFR) on cochlear hair cells of normal and explosion-stricken guinea pigs and the effects of epidermal growth factor (EGF) and dexamethason e (DXM) treatment for blast hearing loss. Methods Immunohistochemical technique and auditory brainstem response (ABR) test were used. Result s Scattered expression of EGFR was seen in inner hair cells (IHCs) and outer hair cells (OHCs) in normal guinea pigs. Segmentally distributi ng positive reaction was also located in stereocilia of hair cells. Di stribution of EGFR reaction was seen in the cytoplasm of IHC 24 hours after exposure to blasts, and in the stereocilia of IHC and the cuticu lar plate of OHC 72 hours postexposure. At one week EGFR reaction in h air cells increased obviously and part of OHC stereocilia also showed positive reaction. EGFR reaction reduced at two weeks, though positive reaction could still be found in the stereocilia of hair cells at one month. Combination of EGF and DXM administrations promoted hearing re covery significantly. Conclusions The healing of injured hair cells ma y be related to EGF.