Glutamate-like Immunoreactivity During Hair Cell Recovery After Gentamicin Exposure in the Chinchilla Vestibular Sensory Periphery

• Published in: The Laryngoscope 1999-07, Vol.109 (7), p.1037-1044
• Main Authors: Chin, Kenley W., Lopez, Ivan, Lee, Seung-Chul, Honrubia, Vicente
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Chinchilla; Crista ampullaris; Drug toxicity and drugs side effects treatment; Ent. Stomatology; gentamicin; Gentamicins - toxicity; glutamate-like; Glutamic Acid - metabolism; hair cell recovery; Hair Cells, Vestibular - drug effects; Hair Cells, Vestibular - metabolism; Hair Cells, Vestibular - ultrastructure; Immunohistochemistry; immunoreactivity; Investigative techniques, diagnostic techniques (general aspects); Labyrinth Supporting Cells; Male; Medical sciences; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Pharmacology. Drug treatments; Toxicity: respiratory system, ent, stomatology
• ISSN: 0023-852X; 1531-4995
• DOI: 10.1097/00005537-199907000-00005

Objective: Determine the expression of glutamate by immunohistochemistry in normal and recovering vestibular hair cells in the chinchilla crista ampullaris after gentamicin ototoxicity. Study Design: In five groups of three animals each, ototoxicity was produced by placing gentamicin (50 μg)‐impregnated Gelfoam pellets within the perilymphatic space of the superior semicircular canal. Animals were sacrificed at 1, 2, 4, 8, and 16 weeks after treatment. A group of normal (n=3) animals was also processed. Methods: For the detection of glutamate the inner ears of these animals were dissected, and the horizontal cristae ampullaris embedded in plastic. Two‐micron‐thick tissue sections were obtained and incubated with monoclonal antibodies against glutamate. The immunoreaction was detected using the avidinbiotiny‐lated‐complex technique and diaminobenzidine was the chromogen. Results: Normal sensory epithelia demonstrated type I and type II hair cells with moderate glutamate‐like immunoreactivity. Supporting cells demonstrated no glutamate‐like immunoreactivity. Afferent nerve fibers and calyxes surrounding type I hair cells demonstrated strong glutamate‐like immunoreactivity. At 1 and 2 weeks after treatment the few type II hair cells surviving ototoxic treatment (15%–18%) contained moderate glutamate‐like immunoreactivity, supporting cells showed no immunoreactivity, and nerve terminals and fibers displayed strong immunoreactivity. At 4 and 8 weeks after treatment, recovered hair cells (80%) had greater glutamate‐like immunoreactivity when compared with normal hair cells, supporting cells displayed no glutamate‐like immunoreactivity, and afferent fibers contained strong glutamate‐like immunoreactivity. At 16 weeks, glutamate‐like immunoreactivity in hair cells returned to normal level. Conclusion: Glutamate may be used as an indicator of hair cell differentiation and as an index of the molecular recovery of hair cells after ototoxicity.