Meeting Abstract
Ectothermic animals that remain active during the winter despite lower temperatures utilize adaptive mechanisms to maintain metabolic activity in the cold to fulfill the energy requirements for survival. Mechanisms that underpin such acclimation include increases in oxidative capacity, membrane fluidity, and O2 diffusion, which, though beneficial to the maintenance of homeostasis in the cold, may also result in deleterious effects such as enhanced proton leak, lipid peroxidation, and oxidative stress. Our own research shows that the Eastern red spotted newt (Notophthalamus viridescens viridescens) increases the polyunsaturated fatty acid (PUFA) composition of cellular membranes in winter, which is in turn correlated with higher metabolic enzyme activity, and a higher rate of whole-animal O2 consumption. Since PUFAs are especially sensitive to oxidative attack, we hypothesized that the newt must possess defenses to combat oxidative stress and membrane peroxidation to maintain physiologic homeostasis during winter acclimation. To this end we measured lipid peroxidation in liver and muscle tissue of newts collected in summer and winter. We found an increase in the lipid peroxidation of liver but not skeletal muscle membranes in winter. This was correlated with a reduction in the reduced glutathione (GSH) content and of the activities of GSH-dependent antioxidant enzymes in liver, while in muscle GSH content and the activities of catalase and GSH-s-transferase (GST) remained unchanged. This work reveals an antioxidant defense mechanism in the newt, the maintenance of which during seasonal acclimation appears to protect membranes from oxidative injury in a tissue-specific manner.
