Ca²⁺ homeostasis and redox balance in antarctic sea organisms: Effects of temperature and of environmental contaminants

In this research, three lines of investigation were pursued. (1) In vivo effects of temperature and H₂O₂ were evaluated in the limpet Nacella concinna. Production of reactive oxygen species was assessed with the dihydrorhodamine 123 fluorescent probe, lysosome alterations with histochemical techniques, and antioxidant responses through Superoxide dismutase and catalase assays. Data suggest that Nacella spring migrations to intertidal levels, where rises in temperature occur, induce oxidative stress and antioxidant response. (2) In the scallop Adamussium colbecki, the sarcoplasmic reticulum Ca²⁺ ATPase was characterized and heavy metal effects were assessed. An IC₅₀ of 0.9 μ? was found for Hg²⁺ and of 3 μ? for Cd²⁺. (3) Effects of Cu²⁺, Cd²⁺, and Hg²⁺ (2.5 μ?), and of temperature on Ca²⁺ homeostasis and cell viability were assessed in the ciliate Euplotes focardii. Ca²⁺ homeostasis and cell viability were altered by Hg²⁺ at a temperature of 0° C and above, and by Cu²⁺ and Cd²⁺ at 10° C and above. Temperature alone was effective at 20° and 30° C, suggesting that rises in temperature cause an increased cell sensitivity to environmental contaminants.