title: The maturation state of the auditory nerve and brainstem in rats exposed to lead acetate and supplemented with ferrous sulfate.
abstract: BACKGROUND
  The literature has reported the association between lead and auditory effects, based on clinical and experimental studies. However, there is no consensus regarding the effects of lead in the auditory system, or its correlation with the concentration of the metal in the blood.
  
  
  OBJECTIVE
  To investigate the maturation state of the auditory system, specifically the auditory nerve and brainstem, in rats exposed to lead acetate and supplemented with ferrous sulfate.
  
  
  METHODS
  30 weanling male rats (Rattus norvegicus, Wistar) were distributed into six groups of five animals each and exposed to one of two concentrations of lead acetate (100 or 400mg/L) and supplemented with ferrous sulfate (20mg/kg). The maturation state of the auditory nerve and brainstem was analyzed using Brainstem Auditory Evoked Potential before and after lead exposure. The concentration of lead in blood and brainstem was analyzed using Inductively Coupled Plasma-Mass Spectrometry.
  
  
  RESULTS
  We verified that the concentration of Pb in blood and in brainstem presented a high correlation (r=0.951; p<0.0001). Both concentrations of lead acetate affected the maturation state of the auditory system, being the maturation slower in the regions corresponding to portion of the auditory nerve (wave I) and cochlear nuclei (wave II). The ferrous sulfate supplementation reduced significantly the concentration of lead in blood and brainstem for the group exposed to the lowest concentration of lead (100mg/L), but not for the group exposed to the higher concentration (400mg/L).
  
  
  CONCLUSIONS
  This study indicate that the lead acetate can have deleterious effects on the maturation of the auditory nerve and brainstem (cochlear nucleus region), as detected by the Brainstem Auditory Evoked Potentials, and the ferrous sulphate can partially amend this effect.
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Odontologia de Bauru, Bauru, SP, Brazil. Electronic address: fernandazucki@hotmail.com.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Zucki
authors.affiliation: National Institute for Occupational Safety and Health (NIOSH), Atlanta, USA.
authors.forename: Thais C
authors.initials: TC
authors.lastname: Morata
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Odontologia de Bauru, Departamento de Fonoaudiologia, Bauru, SP, Brazil.
authors.forename: Josilene L
authors.initials: JL
authors.lastname: Duarte
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Odontologia de Bauru, Departamento de Fonoaudiologia, Bauru, SP, Brazil.
authors.forename: Maria Cecília F
authors.initials: MCF
authors.lastname: Ferreira
authors.affiliation: Universidade Estadual Paulista "Júlio de Mesquita Filho" (UNESP), Departamento de Engenharia de Produção, Bauru, SP, Brazil.
authors.forename: Manoel H
authors.initials: MH
authors.lastname: Salgado
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Odontologia de Bauru, Departamento de Fonoaudiologia, Bauru, SP, Brazil.
authors.forename: Kátia F
authors.initials: KF
authors.lastname: Alvarenga
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000187:drug effects*; D003056:Cochlear Nerve / Q000187:drug effects*; D016057:Evoked Potentials, Auditory, Brain Stem; D005296:Ferrous Compounds / Q000008:administration & dosage*; D007854:Lead / Q000097:blood / Q000633:toxicity*; D008297:Male; D023421:Models, Animal; D009942:Organometallic Compounds / Q000009:adverse effects*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D005296:Ferrous Compounds; D009942:Organometallic Compounds; D007854:Lead; C020748:ferrous sulfate; C008261:lead acetate
keywords: Acetato de chumbo; Auditory evoked potentials; Audição; Blood lead levels; Ferrous sulfate; Hearing; Lead acetate; Níveis de chumbo no sangue; Potenciais evocados auditivos; Sulfato ferroso