Meeting Abstract

P1.54  Thursday, Jan. 3  Divers vs Hibernators: Are Enzyme Activities Preserved Under Varying Temperatures? PEARSON, L.E.**; GULLET, K.C.; FLORANT, G.L.; KANATOUS, S.B.; Colorado State University, Fort Collins; Xavier University, Cincinnati, Ohio; Colorado State University, Fort Collins; Colorado State University, Fort Collins linnea.pearson@colostate.edu

When faced with extreme temperature variation, activities of metabolic enzymes in homeothermic terrestrial mammals are directly correlated with temperature: a decrease in temperature causes a decrease in enzyme function. Heterothermic terrestrial mammals (i.e. hibernators) undergo extreme temperature fluctuations during the winter months while experiencing torpor. However, upon arousal, there is no net loss of bodily function. In this study, we looked at the physiological adaptations in two extreme mammalian conditions: a diving mammal, a homeotherm, able to maintain function at low temperatures, and a hibernator, the heterotherm that decreases activity in response to a decrease in temperature. To accomplish this, we measured enzymatic activity in cardiac and skeletal muscle of hibernating (yellow-bellied marmot, Marmota flaviventris), diving (harbor seal, Phoca vitulina), and terrestrial (house mouse, Mus musculus) mammals. The activities of key aerobic, anaerobic and antioxidant enzymes were measured at varying temperatures (10°, 15°, 25°, 37° and 40°C) in skeletal and cardiac muscle. Surprisingly, our results indicate that there was no direct correlation between temperature and enzyme activity in the homeothermic diving mammal. In addition, the enzyme activity of the diving mammal showed a similar pattern of activity in response to temperature variation as the hibernating mammal, with greater enzyme activity in the hibernating mammal. Our results suggest there are similar adaptations in the cardiac and skeletal muscles of diving and hibernating mammals under varying temperatures that preserves enzyme function even at low temperatures.