Response of antioxidant defence systems to thermal stress in the Antarctic clam Laternula elliptica

The effects of thermal stress on antioxidant defences in tissues of the Antarctic clam Laternula elliptica were evaluated and the activities of some antioxidant enzymes, and levels of total glutathione (GSH) and protein carbonyl (PC) in digestive gland and gill over 0-4 days under extreme thermal stress (10°C) were measured. Superoxide dismutase activity was slightly higher after one day of thermal stress, although catalase activity was not altered significantly in either digestive gland or gill tissues. Thermal stress was associated with a significant increase in the activity of GSH-related antioxidant enzymes. Glutathione peroxidase and glutathione reductase activities increased up to 1.8- and 2.0-fold, respectively, after two days of thermal stress. Glutathione S-transferase activity drastically increased, to over 3.4- and 4.2-fold in digestive gland and gill, respectively, and remained high on day four. GSH levels also increased in both tissues and remained high on day four. PC content, a marker of protein oxidation, increased after two days of thermal stress. There is evidence that GSH-related antioxidant defence plays a significant role in relation to potential toxicity from reactive oxygen species during thermal stress.