Redox profile in liver of Leporinus macrocephalus exposed to different dissolved oxygen levels A. P. K. Riffel • L. O. Garcia • I. A. Finamor • E. M. H. Saccol • M. Meira • C. Kolberg • A. Horst • W. Partata • S. Llesuy • B. Baldisserotto • M. A. Pavanato Received: 25 April 2011 / Accepted: 24 September 2011 / Published online: 8 October 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Aquatic organisms are continuously exposed to environmental variations, which can lead to physiolog- ical and biochemical alterations. Leporinus macrocephalus, known as piavuc ¸u, is a migratory species that may be exposed to variations in dissolved oxygen levels. Studies evaluating oxidative changes undergone by this species in these conditions are scarce. Therefore, this investigation aimed at evaluating oxidative alterations in L. macrocephalus exposed to different oxygen levels for 96 h: 6.12 ± 0.18, 3.99 ± 0.17, 3.22 ± 0.17, 2.47 ± 0.30 and 0.710 ± 0.07 mg L -1 . At the end of the experimental period, fish were euthanized and livers used to determine lipid hydro- peroxides, thiobarbituric acid reactive substances, catalase, glutathione-S-transferase, superoxide dismu- tase and thiol groups, which are an indirect measure of reduced glutathione. Results indicated a decrease in the studied parameters in hypoxic situations, suggest- ing a possible metabolic depression. Keywords Oxidative stress Á Hypoxia Á Lipid peroxidation Á Antioxidants Introduction The aquatic environment presents natural daily and/or seasonal variations in dissolved oxygen levels. Such changes are due to high temperatures associated with organic decay and consumption by aquatic organisms, as well as anthropogenic action (Diaz and Rosemberg 1995; Wu 1999; Sampaio et al. 2008). The fluctuations in aquatic oxygen levels can affect the distribution of ectotherms, especially fish (Lushchak and Bagnyuk- ova 2007). Some environmental conditions may lead to an imbalance between the generation of reactive oxygen species (ROS), also referred to as pro- oxidants, and the rates of antioxidants, whose action protects the cell against oxidation and ROS. If ROS is A. P. K. Riffel Á L. O. Garcia Á I. A. Finamor Á E. M. H. Saccol Á B. Baldisserotto Á M. A. Pavanato (&) Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, Brazil e-mail: amaliapavanato@yahoo.com.br Present Address: L. O. Garcia Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil M. Meira Departamento de Morfologia, Universidade Federal de Santa Maria, Santa Maria, Brazil C. Kolberg Departamento de Fisiologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil A. Horst Á W. Partata Departamento de Fisiologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil S. Llesuy Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires, Buenos Aires, Argentina 123 Fish Physiol Biochem (2012) 38:797–805 DOI 10.1007/s10695-011-9563-3