title: Rapid alteration of cellular redox homeostasis upon exposure to cadmium and mercury in alfalfa seedlings.
abstract: Here, the kinetics of oxidative stress responses of alfalfa (Medicago sativa) seedlings to cadmium (Cd) and mercury (Hg) (0, 3, 10 and 30 microm) exposure, expanding from a few minutes to 24 h, were studied. Intracellular oxidative stress was analysed using 2',7'-dichlorofluorescin diacetate and extracellular hydrogen peroxide (H(2)O(2)) production was studied with Amplex Red. Growth inhibition, concentrations of ascorbate, glutathione (GSH), homoglutathione (hGSH), Cd and Hg, ascorbate peroxidase (APX) activity, and expression of genes related to GSH metabolism were also determined. Both Cd and Hg increased cellular reactive oxygen species (ROS) production and extracellular H(2)O(2) formation, but in different ways. The increase was mild and slow with Cd, but more rapid and transient with Hg. Hg treatments also caused a higher cell death rate, significant oxidation of hGSH, as well as increased APX activity and transient overexpression of glutathione reductase 2, glutamylcysteinyl synthetase, and homoglutathione synthetase genes. However, Cd caused minor alterations. Hg accumulation was one order of magnitude higher than Cd accumulation. The different kinetics of early physiological responses in vivo to Cd and Hg might be relevant to the characterization of their mechanisms of toxicity. Thus, high accumulation of Hg might explain the metabolism poisoning observed in Hg-treated seedlings.
authors.affiliation: Laboratorio de Fisiología Vegetal, Departamento de Biología and.|Departamento de Química Agrícola, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Ortega-Villasante
authors.affiliation: Laboratorio de Fisiología Vegetal, Departamento de Biología and.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Hernández
authors.affiliation: Departamento de Nutrición Mineral, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Avd. Montañana 1005, 50059 Zaragoza, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Rellán-Álvarez
authors.affiliation: Laboratorio de Fisiología Vegetal, Departamento de Biología and.
authors.forename: Francisca F
authors.initials: FF
authors.lastname: Del Campo
authors.affiliation: Departamento de Química Agrícola, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Ramón O
authors.initials: RO
authors.lastname: Carpena-Ruiz
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects*; D007700:Kinetics; D000455:Medicago sativa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008628:Mercury / Q000378:metabolism / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*