Abstract
IntroductionThe 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. ObjectiveTo 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. Methods30 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. ResultsWe 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). ConclusionThis 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.
Highlights
The literature has reported the association between lead and auditory effects, based on clinical and experimental studies
Previous studies that examined the effect of Pb on the brain antioxidant system and the central auditory system, did not confirm a protective effect of Fe in the auditory cortex.[12,13]
The purpose of the present study was to analyze the maturation state of the auditory nerve and brainstem in rats exposed to lead acetate, as well as if the administration of ferrous sulfate prevented the adverse effects of lead acetate
Summary
The literature has reported the association between lead and auditory effects, based on clinical and experimental studies. Objective: To investigate the maturation state of the auditory system, the auditory nerve and brainstem, in rats exposed to lead acetate and supplemented with ferrous sulfate. 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). A study[8] presented a review about the beneficial effects of different antioxidants in preventing Pb body burden and oxidative stress It finds that the administration of natural or synthetic antioxidants has been shown to be of benefit in the prevention and attenuation of metal induced biochemical alterations, but the human studies are still limited in this regard. Previous studies that examined the effect of Pb on the brain antioxidant system and the central auditory system, did not confirm a protective effect of Fe in the auditory cortex.[12,13]
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