TRANSFORMING-GROWTH-FACTOR-ALPHA TREATMENT ALTERS INTRACELLULAR CALCIUM LEVELS IN HAIR-CELLS AND PROTECTS THEM FROM OTOTOXIC DAMAGE IN-VITRO

To determine if transforming growth factor alpha (TGF alpha) pretreatm ent protects hair cells from aminoglycoside induced injury by modifyin g their intracellular calcium concentration, we assayed hair cell calc ium levels in organ of Corti explants both before and after aminoglyco side (i.e. neomycin, 10(-3) M) exposure either with or without growth factor pretreatment. After TGF alpha (500 ng/ml) treatment, the intrac ellular calcium level of hair cells showed a five-fold increase as com pared to the levels observed in the hair cells of control cultures. Af ter ototoxin exposure, calcium levels in hair cells of control explant s showed an increase relative to their baseline levels, while in the p resence of growth Factors pretreatment, hair cells showed a relative r eduction in calcium levels. Pretreatment of organ of Corti explants af forded significant protection of hair cell stereocilia bundle morpholo gy From ototoxic damage when compared to explants exposed to ototoxin alone. This study correlates a rise in hair cell calcium levels with t he otoprotection of hair cells by TGF alpha in organ of Corti explants . (C) 1997 ISDN.