IOS: Acclimation to Hypoxia in Deer Mice

University Of California-Riverside, Riverside CA

Investigators

Abstract

Deer mice inhabit the broadest altitudinal distribution of any North American mammal, from below sea level (Death Valley) to above 4000 m where hypoxic conditions are the norm and the deer mice must adapt their physiology to satisfy oxygen demand. It appears from recent research that previously described hemoglobin/genetic adaptations exert very modest effects on oxygen acquisition and are insufficient alone to explain the success and activity levels of deer mice at high altitude. Deer mice also display changes in organ sizes (e.g., heart, lung) that vary along the altitude gradient and are correlated with improved aerobic performance necessary for high levels of activity. This project will investigate the extent to which changes in lung size and function contribute to the observed increases in activity in adult mice acclimated to high altitude. Students will participate in all data collection aspects of the proposed research and contribute to the development of educational modules for undergraduate classes and outreach efforts to the public and citizen science workshops in the Southern California region. Results from the study will be further disseminated through publication in peer-reviewed journals and presentations at scientific meetings. Preliminary data from the principle investigator's lab suggests that the capacity of the lung to deliver oxygen at high altitude is the first critical limit in the oxygen cascade and that, in deer mice, the lung has the capacity to remodel to meet that demand. Such pulmonary plasticity would be highly adaptive if species are moving upward in elevation as the climate becomes warmer. This project will therefore test the hypothesis that some animals have the capacity to remodel lung architecture and optimize function throughout their lives. Changes in the cardio-pulmonary tissues between the high- and low-altitude acclimated mice will be assessed through histologic and physiologic assays. Modified gas composition will be used in direct respirometry tests of lung performance in control (normoxic) and altitude-acclimated animals. Lung volume, alveolar surface area, capillary density and blood gas composition will be tested to determine the extent to which organ size, architecture, and composition changes contribute to high altitude acclimation. Results from this study will inform our understanding of how small mammal populations that are forced to move to higher altitudes and harsh or variable conditions as a result of climate change will cope with their relocation.