Interaction of oxygen supply, oxidative stress, and molecular defence systems during temperature stress in fishes.

• Main Author: Heise, Katja
• Format: Thesis
• Language: unknown
• Published: 2005
• Subjects: Antarc*; Antarctic
• Online Access: https://epic.awi.de/id/eprint/14703/; https://hdl.handle.net/10013/epic.24942

Oxygen is the essential substrate for oxidativeenergy production, but oxygen exposure has to belimited because of the damaging effects of reactiveoxygen specie (ROS). Thus, the regulation of oxygenhomeostasis within a narrow physiological range iscrucial for all aerobic life. In marine ectotherms,temperatures outside the species specific optimumrange, which is enclosed by the pejus temperatures(Tp), are supposed to cause progressively decreasingoxygen levels in body fluids and tissues, i.e.functional hypoxia. When critical temperatures (Tc)are reached, transition to anaerobic energyproduction can be observed. In my doctoral study Itested the hypothesis that temperature inducedhypoxia entails oxidative stress, i.e. unbalancedROS production. Moreover, temperature-inducedhypoxia was suggested to induce physiologicaladjustments mediated by the hypoxia inducibletranscription factor (HIF-1), i.e. the masterregulator of oxygen homeostasis.I investigated the long-term influence ofenvironmental temperature and the short-term effectof graded temperature stress on oxidative stressmarkers and the HIF-1 response in the liver ofmarine fish from different latitudes under in vivoconditions.The Antarctic zoarcid Pachycara brachycephalum, keptat control temperature (0°C) was compared to winteracclimatised (6°C) con-familial temperate Zoarcesviviparus. A highly oxidised glutathione redox ratioand elevated microsomal lipid radical formationrates in P. brachycephalum reflected the increasedsusceptibility of polar animals for oxidative stressand lipid peroxidation. However, high glutathionelevels appeared to buffer elevated lipid radicalformation in P. brachycephalum and to charge theliver tissue with a high antioxidant capacity.Consequently, oxidative damage markers were lowunder control conditions (0°C) as well as duringwarm acclimation to 5°C, when compared to thetemperate species. In line with cold enhancedoxidative stress, seasonal temperature changeswithin the natural temperature range of thetemperate Z. viviparus caused higher ...