[An in vitro rapid evaluation of drug-induced ototoxicity and of reductive effect of calcium on aminoglycoside ototoxicity using organ culture].

The ototoxicity of aminoglycoside and anticancer platinum drug was analysed using an organ culture system. The effect of calcium antagonism on aminoglycoside ototoxicity was investigated by the same system. The inner ears of mice, 16-day embryos, were cultured for 5 days with or without gentamicin (GM) or kanamycin (KM) or streptomycin (SM), or ribostamycin (RSM), including 1, 10, 100, or 1000 micrograms/ml respectively. The 21st gestational day-inner ear was cultured in vitro during 4 days with or without Cisplatin (CDDP) or platinum analog DWA2114R (DWA), including 0.1, 1, or 10 micrograms/ml, respectively. The 16th gestational day-inner ear was cultured in vitro for 5 days with 10 micrograms/ml KM, adding 5 mM Ca2+ or 10 mM Ca2+ to the culture medium. The damages of crista ampullaris and macula utriculi of cultured inner ear were estimated according to the ototoxicity score based on morphological changes by a light microscopic observation of serial sections of the materials. We defined four grades for the damages according to the following criteria; grade 1: damage of apical surface of the hair cells, grade 2: the existence of debris in the endolymph space, grade 3: disappearance of the hair cells, grade 4: degeneration of the supporting cells. Using this system following results were obtained: 1) the effect of aminoglycoside was dose dependent, 2) the order of ototoxicity was following; GM greater than KM greater than SM greater than RSM, 3) the drug concentration of 1000 micrograms/ml is sufficient to study its ototoxic potential in this system, 4) the effect of both CDDP and DWA was obvious at a concentration of 0.1 microgram/ml, 5) DWA showed almost the same ototoxicity as CDDP at the same concentration, 6) Adding 5 mM Ca2+ or 10 mM Ca2+ to the culture medium, the ototoxic damage induced by 10 micrograms/ml of KM was not noticed. A protective effect of Ca2+ against KM ototoxicity was observed in vitro. This organ culture and ototoxicity score system can serve as a useful and adequate model system for evaluating the ototoxicity.