Journal of Thermal Biology 32 (2007) 261–269 Adaptive changes in interscapular brown adipose tissue during reacclimation after cold: The role of redox regulation Biljana Buzadzˇ ic´ a , Aleksandra Korac´ b , Vesna Petrovic´ a , Ana Vasilijevic´ a , Aleksandra Jankovic´ a , Bato Korac´ a,Ã a Department of Physiology, Institute for Biological Research, Sinisˇa Stankovic´, University of Belgrade, Bulevar Despota Stefana 142, 11060 Belgrade, Serbia b Institute of Zoology, Faculty of Biology, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia Received 10 October 2006; accepted 24 January 2007 Abstract 1. The level of antioxidative defence, intensity of sympathetic innervation, expression of uncoupling protein 1 (UCP1), and ultrastructure of interscapular brown adipose tissue (IBAT) were studied in rats acclimated to room (2271 1C), low temperature (471 1C, 45 days) and during reacclimation to 22 1C (days 1, 3, and 7). 2. The cold-induced increase in catalase, glutathione peroxidase, glutathione reductase, thioredoxin reductase, as well as a decrease in the activities of CuZn- and Mn-superoxide dismutases, shows specific dynamics of restitution during reacclimation to 22 1C. 3. The intensity of the cold-induced enhancement of the sympathetic innervation and UCP1 expression gradually decreases during reacclimation to 22 1C, but with the seventh day level still higher compared to the animals acclimated to room temperature. 4. Electron-microscopy study of IBAT shows that changes of the strongly activated tissue in cold undergo gradual restitution during reacclimation to 22 1C, but are observed already on the first day through a massive accumulation of glycogen, accompanied by a change in the lipid profile. r 2007 Elsevier Ltd. All rights reserved. Keywords: Redox regulation; Brown adipose tissue; Uncoupling; Antioxidative defence; Cold; Reacclimation 1. Introduction The redox equilibrium plays an important role in maintaining the total homeostasis of cells and tissues (Wiese et al., 1995; Kamata and Hirata, 1999). It has been shown to be tissue specific, and to change in various states: hyperplasia, cancer, cardiovascular and neurodegenerative diseases, etc. (Halliwell and Gutteridge, 1985; De Bono, 1994; Toyokuni et al., 1995; Davies, 1999). Maintenance of this equilibrium depends on the endogenous antioxidative defence (AD). The AD primarily includes the following enzymes: superoxide dismutase (CuZnSOD and MnSOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR), as well as glutathione (GSH), necessary not only as an antioxidant, but also as a cofactor of numerous enzymes and the most significant molecule for maintaining the redox environment in the cells (McCord and Omar, 1993; Jacob, 1995; Aruoma, 1996). Also, AD shows plasticity in the response to intensity and metabolic tissue profile (Halliwell and Gutteridge, 1990; Spasic´ et al., 1993; Petrovic´ et al., 2006). On the other hand, interscapular brown adipose tissue (IBAT) shows extraordinary ability to remodel, given that its thermogenic capacity depends on the number of brown adipocytes, mitochondria, and the concentration of un- coupling protein 1 (UCP1) present (Lin and Klingenberg, 1982; Rial et al., 1983; Bukowiecki et al., 1986; Buzadzˇ ic´ et al., 1990; Nedergaard et al., 2001; Cannon and Nedergaard, 2004). These adaptive changes are directly mediated by sympathetic stimulation (Bukowiecki et al., 1978; Arch et al., 1984). These processes in IBAT are induced by different stimuli. External temperature is among the most potent ARTICLE IN PRESS www.elsevier.com/locate/jtherbio 0306-4565/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtherbio.2007.01.015 Ã Corresponding author. Tel.: +381 11 207 8307; fax: +381 11 2761 433. E-mail address: koracb@ibiss.bg.ac.yu (B. Korac´).