title: Sub-chronic exposure to methylmercury at low levels decreases butyrylcholinesterase activity in rats.
abstract: In this study, we examined the effects of low levels and sub-chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [delta-aminolevulinic acid dehydratase (delta-ALA-D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 microg/kg/day) by gavage; (Group III) received MeHg (100 microg/kg/day). The time of exposure was 90 days. BuChE and ALA-D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA-D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = -0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA-D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long-term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.
authors.affiliation: Department of Clinical, Toxicological and Bromatological Analysis, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Juliana
authors.initials: J
authors.lastname: Valentini
authors.forename: Juliana
authors.initials: J
authors.lastname: Vicentini
authors.forename: Denise
authors.initials: D
authors.lastname: Grotto
authors.forename: Raquel
authors.initials: R
authors.lastname: Tonello
authors.forename: Solange C
authors.initials: SC
authors.lastname: Garcia
authors.forename: Fernando
authors.initials: F
authors.lastname: Barbosa
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002091:Butyrylcholinesterase / Q000097:blood / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008767:Methylmercury Compounds / Q000008:administration & dosage / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D000623:Porphobilinogen Synthase / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D015415:Biomarkers; D008767:Methylmercury Compounds; D008315:Malondialdehyde; D002091:Butyrylcholinesterase; D000623:Porphobilinogen Synthase