L-carnitine (LC) protects cells from peroxidative damage. In this study, we tested whether L-carnitine (LC) prevents radiation-induced cochlear damage after total cranial irradiation (radiotherapy; RT). Male albino guinea pigs were randomly distributed in 3 groups. The Control group (n = 11) received neither LC nor irradiation, but saline solution ip and sham irradiation for 5 days. The RT group (n = 32) received saline solution ip as placebo therapy and exposure to total cranial irradiation of

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... 33 Gy in 5 fractions of 6.6 Gy/day on 5 successive days, with a calculated (alpha/beta = 3.5) biological effective dose of fractionated irradiation equal to 60 Gy conventional fractionation. The LC + RT group (n = 36) received total cranial irradiation, plus LC (100 mg/kg/day, ip) for 5 days. The guinea pigs were killed at 4, 24, or 96 hr after the last dose of RT and the cochleas were enucleated for histopathologic examination. There was no cochlear degeneration in the control group. In the RT group, total cranial irradiation caused degeneration in stria vascularis (SV), spiral ganglion (SG), outer hair cells (OHC), and inner hair cells (IHC) of cochleas at 4, 24, and 96 hr. In the LC + RT group, LC administration reduced radiation-induced cochlear degeneration in SV and SG at 4, 24, and 96 hr, and in OHC and IHC at 24 and 96 hr (p <0.05). Thus, this study shows that L-carnitine can ameliorate radiation-induced cochlear damage in guinea pigs.