P2.19 Tuesday, Jan. 5 The Effect of Mitochondrial Ultrastructure on Function in Antarctic Notothenioid Fishes MUELLER, Irina A*; O’BRIEN, Kristin M; University of Alaska Fairbanks; University of Alaska Fairbanks email@example.com
The loss of hemoglobin (Hb) and myoglobin (Mb) in the heart ventricle of Antarctic icefishes (Family Channichthyidae) is correlated with striking alterations in mitochondrial ultrastructure. The aim of this study was to determine if the differences in mitochondrial structure affect function, close to physiological temperature (2°C) and at the elevated temperature of 10°C. State III respiration rates and proton leak rates were measured in mitochondria isolated from the heart ventricle of Chaenocephalus aceratus (-Hb/-Mb), Chionodraco rastrospinosus (-Hb/+Mb), Notothenia coriiceps (+Hb/+Mb) and Gobionotothen gibberifrons (+Hb/+Mb) at 2°C and 10°C. Rates of production of reactive oxygen species (ROS) were also measured at 2°C and 10°C in mitochondria isolated from C. aceratus and N. coriiceps. State III respiration rates were not significantly different among the species at 2°C or 10°C. Rates of proton leak increased in response to an increase in temperature in all species, but mitochondria from icefishes were always more tightly coupled than mitochondria of red-blooded notothenioids. Differences in mitochondrial coupling were not reflected in differences in transcript levels of uncoupling protein 2. Mitochondrial ROS production increased as temperature increased yet was not significantly different between C. aceratus and N. coriiceps. Addition of respiratory chain inhibitors resulted in a greater increase in ROS production in mitochondria from C. aceratus compared to N. coriiceps, which was correlated with a higher mitochondrial membrane potential in C. aceratus. Summarized, the differences in mitochondrial ultrastructure between icefishes and red-blooded notothenioids affect proton leak, but not state III respiration rates or ROS production under normal physiological conditions.