title: Effects of exposure to multiple trace metals on biochemical, histological and ultrastructural features of gills of a freshwater fish, Channa punctata Bloch.
abstract: The trace metals are frequently encountered as mixtures of essential and non-essential elements. Therefore, evaluation of their toxic effects individually does not offer a realistic estimate of their impact on biological processes. We studied effects of a mixture of four essential and toxic metals (Cu, Cd, Fe and Ni) on biochemical and morphological characteristics of the gills of a biomarker freshwater fish Channa punctata (Bloch) using environmentally relevant concentrations. Fish were exposed to metal mixture through tank water for 7, 15 and 30 days. Biochemical studies as well as light microscopy (LM) and scanning electron microscopy (SEM) revealed significant metal exposure-induced alterations in gills. Besides ultastructural changes, activities of antioxidant enzymes such catalase (CAT), glutathione S-transferase (GST) and superoxide dismutase (SOD) were significantly altered in the gills of exposed fish. The reduced glutathione (GSH) was significantly (p<0.001) decreased, while lipid peroxidation (LPO) was significantly (p<0.001) increased. The main alterations in general morphology of fish gills included spiking and fusion of secondary lamellae, formation of club-shaped filaments, and vacuolization and necrosis of filament epithelium in the interlamellar regions. SEM studies showed gradual increase of the density and apical surface area of the chloride cells and transformation of the surface structure of the pavement cells. The results of this study indicate adaptive as well a toxic responses in fish gills exposed to mixture of trace metals. Low concentrations of trace metal appear to compromise the antioxidant defense of gills. Lesions in the gill morphology caused by the effect of low concentrations of trace metals could lead to functional alterations and interference with fundamental processes such as maintenance of osmoregulation, gas exchange and xenobiotic metabolism in the exposed fish populations.
authors.affiliation: Ecotoxicology Laboratory, Department of Medical Elementology and Toxicology, Jamia Hamdard (Hamdard University), New Delhi 110062, India.
authors.forename: Suwarna
authors.initials: S
authors.lastname: Pandey
authors.forename: Suhel
authors.initials: S
authors.lastname: Parvez
authors.forename: Rizwan Ahamd
authors.initials: RA
authors.lastname: Ansari
authors.forename: Mehboob
authors.initials: M
authors.lastname: Ali
authors.forename: Manpreet
authors.initials: M
authors.lastname: Kaur
authors.forename: Faisal
authors.initials: F
authors.lastname: Hayat
authors.forename: Firoz
authors.initials: F
authors.lastname: Ahmad
authors.forename: Sheikh
authors.initials: S
authors.lastname: Raisuddin
mesh_terms: D000818:Animals; D019256:Cadmium Chloride / Q000633:toxicity; D003300:Copper / Q000633:toxicity; D004847:Epithelial Cells / Q000187:drug effects / Q000648:ultrastructure; D005296:Ferrous Compounds / Q000633:toxicity; D005618:Fresh Water; D005880:Gills / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D009336:Necrosis / Q000139:chemically induced / Q000473:pathology; D009532:Nickel / Q000633:toxicity; D010088:Oxidoreductases / Q000378:metabolism; D010473:Perciformes; D018675:Toxicity Tests; D014131:Trace Elements / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D005296:Ferrous Compounds; D014131:Trace Elements; D014874:Water Pollutants, Chemical; C022838:nickel chloride; D003300:Copper; D009532:Nickel; D010088:Oxidoreductases; D005978:Glutathione; D019256:Cadmium Chloride; C029892:cupric chloride; C029451:ferrous chloride