title: Toxicity assessment of the herbicide metolachlor comparative effects on bacterial and mitochondrial model systems.
abstract: Metolachlor is one of the most intensively used chloroacetamide herbicides. However, its effects on the environment and on non-target animals and humans as well as its interference at a cell/molecular level have not yet been fully elucidated. The aim of this study was: firstly, to evaluate the potential toxicity of metolachlor at a cell/subcellular level by using two in vitro biological model systems (a strain of Bacillus stearothermophilus and rat liver mitochondria); secondly, to evaluate the relative sensibility of these models to xenobiotics to reinforce their suitability for pollutant toxicity assessment. Our results show that metolachlor inhibits growth and impairs the respiratory activity of B.stearothermophilus at concentrations two to three orders of magnitude higher than those at which bacterial cells are affected by other pesticides. Also at concentrations significantly higher than those of other pesticides, metolachlor depressed the respiratory control ratio, membrane potential and respiration of rat liver mitochondria when malate/glutamate or succinate were used as respiratory substrates. Moreover, metolachlor impaired the respiratory activity of rat liver mitochondria in the same concentration range at which it inhibited bacterial respiratory system (0.4-5.0 micromol/mg of protein). In conclusion, the high concentration range at which metolachlor induces toxicity in vitro suggests that this compound is safer than other pesticides previously studied in our laboratory, using the same model systems. The good parallelism between metolachlor effects on both models and the toxicity data described in the literature, together with results obtained in our laboratory with other compounds, indicate the suitability of these systems to assess toxicity in vitro.
authors.affiliation: CNC - Centre for Neuroscience and Cell Biology, Zoology Department, Coimbra University, Portugal.
authors.forename: Susana P
authors.initials: SP
authors.lastname: Pereira
authors.forename: Maria A S
authors.initials: MA
authors.lastname: Fernandes
authors.forename: João D
authors.initials: JD
authors.lastname: Martins
authors.forename: Maria S
authors.initials: MS
authors.lastname: Santos
authors.forename: António J M
authors.initials: AJ
authors.lastname: Moreno
authors.forename: Joaquim A F
authors.initials: JA
authors.lastname: Vicente
authors.forename: Romeu A
authors.initials: RA
authors.lastname: Videira
authors.forename: Amália S
authors.initials: AS
authors.lastname: Jurado
mesh_terms: D000081:Acetamides / Q000633:toxicity*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D001411:Geobacillus stearothermophilus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006540:Herbicides / Q000633:toxicity*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000081:Acetamides; D006540:Herbicides; C051786:metolachlor