title: High environmental ammonia elicits differential oxidative stress and antioxidant responses in five different organs of a model estuarine teleost (Dicentrarchus labrax).
abstract: We investigated oxidative status and antioxidant profile in five tissues (brain, liver, gills, muscle and kidney) of European sea bass (Dicentrarchus labrax) when exposed to high environmental ammonia (HEA, 20 mg/L~1.18 mM as NH4HCO3) for 12 h, 2 days, 3.5 days, 7.5 days and 10 days. Results show that HEA triggered ammonia accumulation and induced oxidative stress in all tissues. Unlike other organs, hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulation in liver were restored to control levels. This recovery was associated with a concomitant augmentation in superoxide dismutase (SOD), catalase (CAT), components of glutathione redox cycle (glutathione peroxidase GPX, glutathione reductase, reduced glutathione), ascorbate peroxidase activity and reduced ascorbate content. On the contrary, in brain during prolonged exposure many of these anti-oxidant enzymes were either unaffected or inhibited, which resulted in persistent over-accumulation of H2O2 and MDA. Branchial and renal tissue both involved in osmo-regulation, revealed an entirely dissimilar compensatory response; the former rely mainly on the ascorbate dependent defensive system while the glutathione catalytic pathway was activated in the latter. In muscle, GPX activity first rose (3.5 days) followed by a subsequent drop, counterbalanced by simultaneous increment of CAT. HEA resulted in a relatively mild oxidative stress in the muscle and kidney, probably explaining the modest anti-oxidative responses. Our findings exemplify that oxidative stress as well as antioxidant potential are qualitatively diverse amongst different tissues, thereby demonstrating that for biomonitoring studies the screening of adaptive responses at organ level should be preferred over whole body response.
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium. Electronic address: sinha_cife@rediffmail.com.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Sinha
authors.affiliation: Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, BE-2020 Antwerp, Belgium.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Zinta
authors.affiliation: Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, BE-2020 Antwerp, Belgium; Department of Botany, Faculty of Science, University of Beni-Sueif, Beni-Sueif 62511, Egypt.
authors.forename: Hamada
authors.initials: H
authors.lastname: AbdElgawad
authors.affiliation: Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, BE-2020 Antwerp, Belgium.
authors.forename: Han
authors.initials: H
authors.lastname: Asard
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Ronny
authors.initials: R
authors.lastname: Blust
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Gudrun
authors.initials: G
authors.lastname: De Boeck
mesh_terms: D000641:Ammonia / Q000009:adverse effects*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D060387:Ascorbate Peroxidases / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D001492:Bass / Q000378:metabolism*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002384:Catalysis / Q000187:drug effects; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D013482:Superoxide Dismutase / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000009:adverse effects
chemical_list: D000975:Antioxidants; D014874:Water Pollutants, Chemical; D008315:Malondialdehyde; D000641:Ammonia; D006861:Hydrogen Peroxide; D060387:Ascorbate Peroxidases; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D001205:Ascorbic Acid
keywords: Antioxidant defense system; Brain; European sea bass; Gills; Hydrogen peroxide (H(2)O(2)); Liver; Malondialdehyde (MDA)