title: D-methionine (D-met) significantly rescues noise-induced hearing loss: timing studies.
abstract: We have previously reported rescue from noise-induced auditory brainstem response (ABR) threshold shifts with d-methionine (d-met) administration 1 h after noise exposure. The present study investigated further d-met rescue intervals at 3, 5 and 7 h post-noise exposure. Chinchillas laniger were exposed to a 6 h 105 dB sound pressure level (dB SPL) octave band noise (OBN) and then administered d-met i.p. starting 3, 5, or 7 h after noise exposure; controls received saline i.p. immediately after noise exposure. ABR assessments were performed at baseline and on post-exposure days 1 and 21. Outer hair cell (OHC) loss was measured in cochleae obtained at sacrifice 21 days post-exposure. Administration of d-met starting at any of the delay times of 3-7 h post-noise exposure significantly reduced day 21 ABR threshold shift at 2 and 4 kHz and OHC loss at all hair cell regions measured (2, 4, 6 and 8 kHz). ABR threshold shifts in the control group at 6 and 8 kHz were only 8 and 11 dB respectively allowing little opportunity to observe protection at those 2 frequencies.
authors.affiliation: Department of Surgery, Division of Otolaryngology, Southern Illinois University School of Medicine, PO Box 19629, Springfield, IL 62794-9629, USA. kcampbell@siumed.edu
authors.forename: Kathleen
authors.initials: K
authors.lastname: Campbell
authors.forename: Alex
authors.initials: A
authors.lastname: Claussen
authors.forename: Robert
authors.initials: R
authors.lastname: Meech
authors.forename: Steven
authors.initials: S
authors.lastname: Verhulst
authors.forename: Daniel
authors.initials: D
authors.lastname: Fox
authors.forename: Larry
authors.initials: L
authors.lastname: Hughes
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001933:Brain Stem / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D002682:Chinchilla; D019610:Cytoprotection; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000473:pathology; D006317:Hearing Loss, Noise-Induced / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D008715:Methionine / Q000008:administration & dosage*; D020011:Protective Agents / Q000008:administration & dosage*; D013997:Time Factors
chemical_list: D020011:Protective Agents; D008715:Methionine