Meeting Abstract
Oxygen limitation plays a key role in many pathologies, and yet we still lack a fundamental understanding of the mechanisms responsible for intra- and interspecific variation in hypoxia/anoxia tolerance. Current theory suggests that a better anoxia tolerance primarily involves the ability to maintain cellular energetic status as depletion of ATP leads to detrimental processes (e.g. disruption of ionic homeostasis, depolarization of membranes). In this study, we tested for possible mechanisms that allow Drosophila melanogaster adults to survive longer periods of anoxia than third instar larvae (LT50: ~8 vs. 1 h). During the first two hours, larval ATP fell to <1% of normal and [K+] rose by 50%; survival fell to zero in strong correlation with ATP and [K+]. In adults, during the first two hours, ATP to fell to 2% of normal values, [K+] rose by ~3x, but survival was 100%. During the next six hours, adults maintained high survival, while ATP was maintained at 2% of normal levels, and hemolymph [K+] continued to rise to 5x normal. Over 8 h of anoxia, adults quickly restored hemolymph [K+] if returned to normoxia, despite having hemolymph [K+] levels up to 4.5x greater than resting. In adults exposed to more than 8 h of anoxia, ATP levels decreased further and [K+] continued to rise; both of these variables correlated with decreased survival. The superior anoxia tolerance of adult Drosophila appears to be due to the capacity to maintain and tolerate very low ATP levels, and to the ability to tolerate high extracellular [K+]. This study suggests that a new focus of research in anoxia-tolerance should be the mechanisms by which animals can survive and quickly recover from such energetic and ionic conditions. Supported by NSF IOS1256745.
