title: Antioxidative responses of the tissues of two wild populations of Pelophylax kl. esculentus frogs to heavy metal pollution.
abstract: Heavy metal pollution of the aquatic environment is of great concern worldwide. Heavy metals are capable of inducing oxidative stress by increasing the formation of reactive oxygen species (ROS), and directly affecting the antioxidant defense system (AOS) in living organisms. The frog Pelophylax kl. esculentus is a semiaquatic species with semipermeable skin and a complex lifecycle, and represents a potentially useful bioindicator organism. The aim of this study was to investigate the accumulation of several heavy metals (Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb and Zn), and their effects on selected parameters of the AOS, including the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), phase II biotransformation enzyme glutathione-S-transferase (GST), the total glutathione (GSH) contents and sulfhydryl (SH) group concentrations, as well as cholinesterases (ChEs) activities in the liver, skin and muscle of P. kl. esculentus. Frog samples were collected at two sites (the Danube-Tisza-Danube canal (DTDC) and the river Ponjavica) in Serbia, which are characterized by different levels of metal pollution. Differences between the metal contents in different tissues showed that the skin of frogs from the DTDC accumulated statistically higher concentrations of Cd, Cu, Pb and Zn, while only the Fe concentration was lower. No significant differences between metal concentrations in muscle tissues of frogs from the DTDC and Ponjavica were observed. Examination of the parameters of the AOS revealed that frogs from the DTDC had higher concentrations of GSH in the liver and of SH groups in the skin and muscle, whereas the activities of the antioxidative enzymes SOD, GHS-Px and GR in the liver and of GR in the skin were lower than in frogs from the Ponjavica. The relationship between metal concentrations and AOS parameters showed the highest number of correlations with GSH, GR and CAT, and with Ni, Zn, Hg, Cr and Cd. Based on the results in this study, we concluded that increased concentrations of heavy metals in frog tissues can alter the AOS, which leads to higher concentrations of GSH and SH groups and lower activities of antioxidative enzymes. The response of the AOS to metal pollutants allowed us to make a distinction between different frog tissues, and to conclude that the liver and skin are more suitable for assessing metal-induced oxidative stress in frogs than muscle.
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia. Electronic address: marko.prokic@ibiss.bg.ac.rs.
authors.forename: Marko D
authors.initials: MD
authors.lastname: Prokić
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Slavica S
authors.initials: SS
authors.lastname: Borković-Mitić
authors.affiliation: Faculty of Biology, Institute of Zoology, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia.
authors.forename: Imre I
authors.initials: II
authors.lastname: Krizmanić
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade, Serbia.
authors.forename: Jelena J
authors.initials: JJ
authors.lastname: Mutić
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade, Serbia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Vukojević
authors.affiliation: Faculty of Biology, Chair of Comparative Physiology and Ecophysiology, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Nasia
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Jelena P
authors.initials: JP
authors.lastname: Gavrić
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Svetlana G
authors.initials: SG
authors.lastname: Despotović
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Branka R
authors.initials: BR
authors.lastname: Gavrilović
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Tijana B
authors.initials: TB
authors.lastname: Radovanović
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Slađan Z
authors.initials: SZ
authors.lastname: Pavlović
authors.affiliation: Department of Physiology, Institute for Biological Research "Siniša Stanković", University of Belgrade, Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
authors.forename: Zorica S
authors.initials: ZS
authors.lastname: Saičić
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D002802:Cholinesterases / Q000378:metabolism; D004784:Environmental Monitoring; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D019216:Metals, Heavy / Q000032:analysis / Q000633:toxicity*; D009132:Muscles / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011898:Ranidae / Q000378:metabolism*; D045483:Rivers; D055771:Serbia; D012867:Skin / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D002802:Cholinesterases; D005978:Glutathione
keywords: Antioxidative defense system; Frogs tissues; Heavy metal ions; Oxidative stress; Pelophylax kl. esculentus