Hexachlorobenzene, a dioxin-like compound, disrupts auditory function in rat.
Hexachlorobenzene (HCB) is a dioxin-like compound widely distributed in the environment. In this study, we investigated the effects of HCB on the cochlea. Conscious free-moving rats were given HCB per os daily for 4 weeks at doses of 0.16, 4 or 16 mg/kg in olive oil, whereas the control group received olive oil only. The effects of HCB were evaluated at various time intervals, by measuring auditory nerve acoustic thresholds and plasma thyroid hormone concentration by radioimmunoassay. Histological evaluation involved surface preparation and scanning electron microscopy observations of cochlear hair cells. At a dose of 0.16 mg/kg, HCB induced no loss of acoustic sensitivity, whereas at 4 mg/kg, it induced cochlear sensitivity deficits at the mid-frequencies (2-16 kHz) with complete recovery once treatment was stopped. At a dose of 16 mg/kg, permanent threshold shifts were observed at all frequencies tested (from 1 to 32 kHz). Morphological studies showed no cochlear hair cell loss or alteration of stereocilia. HCB treatment reduced circulating thyroxine concentrations. Thyroidectomy had no effect on cochlear sensitivity in control animals. Thus, HCB is a potent oto-toxicant, and its ototoxicity may be independent of its thyroidal effects.
Hadjab
Saida
S
Laboratoire d'Otologie Neuro-Otologie, EMI 9902 INSERM, Faculté de Médecine Secteur Nord, Université de la Méditerranée, Boulevard Pierre Dramard, 13916 Marseille Cedex 20, France.
Maurel
Daniel
D
Cazals
Yves
Y
Siaud
Philippe
P
D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects*; D016022:Case-Control Studies; D003051:Cochlea / Q000187:drug effects* / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005659:Fungicides, Industrial / Q000008:administration & dosage / Q000633:toxicity*; D006198:Hair Cells, Auditory / Q000648:ultrastructure; D034381:Hearing Loss / Q000139:chemically induced*; D006581:Hexachlorobenzene / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D008855:Microscopy, Electron, Scanning; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology; D013963:Thyroid Hormones / Q000097:blood; D013965:Thyroidectomy
D005659:Fungicides, Industrial; D013963:Thyroid Hormones; D006581:Hexachlorobenzene