SUBSTRATE AND ACUTE TEMPERATURE EFFECTS ON TURTLE HEART AND LIVER-MITOCHONDRIA

The oxidative properties of heart and liver mitochondria from the West ern painted turtle (Chrysemys picta bellii) were characterized on the basis of substrate preferences and temperature sensitivity. Turtle hea rt and liver mitochondria oxidize most substrates at 2- and 10-fold le ss, respectively, than rates obtained from the corresponding rat mitoc hondria. Krebs cycle intermediates, ketone bodies, and glutamate were oxidized at similarly high rates by turtle heart mitochondria (70.0-12 1.2 nmol 0.min(-1).mg protein(-1)). Fatty acylcarnitines were oxidized at approximately one-half of the above rates, and rates of amino acid oxidation were either not detectable or very low. Heart mitochondria oxidize ketone bodies at rates as high as pyruvate plus malate. Liver mitochondria oxidized Krebs cycle intermediates, amino acids, and fatt y acids at similarly low rates (3.0-8.0 nmol 0.min(-1).mg protein(-1)) . Typically, succinate was oxidized at the highest rates, 20.6+/-4.0 a nd 121.2+/-1.2 nmol 0.min(-1).mg protein(-1), for liver and heart, res pectively. Values for the rate of change of oxidation with a 10 degree s C increase (Q(10)) from heart and liver mitochondria oxidizing gluta mate were calculated over the range 25-5 degrees C in 5 degrees C inte rvals; over the range 10-5 degrees C, Q(10) values were 3.2 and 19.8, respectively. Q(10) values calculated over the higher temperature inte rvals were lower. It is suggested that the large difference in tempera ture sensitivity between mitochondria from these two tissues and the a bility of the heart mitochondria to oxidize ketone bodies at high rate s are adaptations to recover from the long anoxic overwintering bouts experienced by this species.