Abstract
This study investigated seasonal variations of antioxidant defense enzyme activities: total, manganese, copper zinc containing superoxide dismutase (Tot SOD, Mn SOD, CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and biotransformation phase II enzyme glutathione-S-transferase (GST) activity in the liver and white muscle of red mullet (Mullus barbatus). The investigations were performed in winter and spring at two localities: Near Bar (NB) and Estuary of the River Bojana (EB) in the Southern Adriatic Sea. At both sites, Mn SOD, GSH-Px, GR and GST activities decreased in the liver in spring. In the white muscle, activities of Mn SOD, GSH-Px, GR and GST in NB decreased in spring. GR decreased in spring in EB, while CAT activity was higher in spring at both sites. The results of Principal Component Analysis (PCA) based on correlations indicated a clear separation of various sampling periods for both investigated tissues and a marked difference between two seasons. Our study is the first report on antioxidant defense enzyme activities in the red mullet in the Southern Adriatic Sea. It indicates that seasonal variations of antioxidant defense enzyme activities should be used in further biomonitoring studies in fish species.
Highlights
Fish as species are on top of the aquatic food chain; as vertebrates, they strongly respond to stress conditions [1]
Our results show that manganese containing superoxide dismutase (Mn SOD) activity was significantly lower in spring in comparison to winter (p < 0.05) in the liver (Figure 2A) at both examined localities, and in white muscle (Figure 2B) in Near Bar (NB) locality
The treatment of overall data by Principal Component Analysis (PCA) indicated a clear separation of various sampling periods for both tissues and a marked difference between seasons
Summary
Fish as species are on top of the aquatic food chain; as vertebrates, they strongly respond to stress conditions [1]. Evaluation of seasonal variations in biomarkers and determination of basal levels in model organisms constitute a research strategy that is widely recommended today This effort overcomes the difficulties involved in field studies, integrating variations in many natural stressors and evaluating the effects of chemical pollution [2]. Studies on oxidative stress biomarkers related to seasonal changes in poikilothermic organisms revealed their strong relationship with metabolic demands [7,8]. It means that lower metabolic rate is accompanied with lower antioxidative defense, but the role of individual components in achievement of homeostasis seams to be different and integrated in antioxidative defense system. Fish are exposed to daily and/or seasonal changes in both water temperatures and oxygen availability; variations in the activity of oxidative stress biomarkers have been demonstrated in several studies and proposed as biomarkers of pollutant-mediated oxidative stress [9,10]
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