Substrate and acute temperature effects on turtle heart and liver mitochondria

Area of Science:

• Comparative physiology
• Mitochondrial respiration
• Animal adaptation

Background:

• Mitochondria are crucial for cellular energy production.
• The Western painted turtle (Chrysemys picta bellii) endures long anoxic overwintering periods.
• Understanding metabolic adaptations is key to explaining species survival strategies.

Purpose of the Study:

• To characterize the oxidative properties of heart and liver mitochondria in the Western painted turtle.
• To compare substrate preferences and temperature sensitivity of turtle mitochondria with rat mitochondria.
• To investigate potential adaptations related to overwintering anoxia.

Main Methods:

• Isolation and characterization of heart and liver mitochondria from Chrysemys picta bellii.
• Measurement of substrate oxidation rates using various substrates (Krebs cycle intermediates, ketone bodies, amino acids, fatty acids).
• Determination of temperature sensitivity (Q10 values) across different temperature ranges.

Main Results:

• Turtle heart and liver mitochondria exhibit lower substrate oxidation rates compared to rat mitochondria.
• Heart mitochondria show high oxidation rates for Krebs cycle intermediates, ketone bodies, and glutamate.
• Liver mitochondria display low oxidation rates for most substrates, with succinate showing the highest rate.
• Significant differences in temperature sensitivity (Q10) were observed between heart and liver mitochondria, particularly at lower temperatures.

Conclusions:

• The distinct substrate preferences and temperature sensitivities of turtle heart and liver mitochondria are likely adaptations.
• High ketone body oxidation in heart mitochondria may aid recovery after anoxic overwintering.
• Differential temperature sensitivity suggests tissue-specific metabolic adjustments for survival during prolonged cold and anoxia.