Aim: This study aimed to compare hyperthermia-induced changes in respiration and generation of reactive oxygen species (ROS) in liver mitochondria derived from animals of different gender and age. Methods: The effects of hyperthermia (40⁻47 °C) on oxidation of different substrates and ROS production were estimated in mitochondria isolated from the liver of male and female rats of the 1⁻1.5, 3⁻4, or 6⁻7 months age. Results: Gender-dependent differences in response of respiration to hyperthermia were the highest at 3⁻4 months of age, less so at 6⁻7 months of age, and only minor at juvenile age. Mild hyperthermia (40⁻42 °C) stimulated pyruvate + malate oxidation in mitochondria of females, but inhibited in mitochondria of males in the 3⁻4 month age group. The resistance of mitochondrial membrane to hyperthermia was the highest at 3⁻4 month males, and the lowest in the 6⁻7 month age group. Inhibition of glutamate + malate oxidation by hyperthermia was caused by thermal inactivation of glutamate dehydrogenase. ROS generation at 37 °C was higher at 1⁻1.5 month of age, but the increase in ROS generation with rise in temperature in this age group was the smallest, and the strongest in 6⁻7 month old animals of both genders. Conclusions: The response to hyperthermia varies during the first 6⁻7 months of life of experimental animals: stronger gender dependence is characteristic at 3⁻4 months of age, while mitochondria from 6⁻7 months animals are less resistant to hyperthermia.
Keywords: age; gender; hyperthermia; liver mitochondria; reactive oxygen species; respiration.