Malondialdehyde content and circadian variations in brain, kidney, liver, and plasma of mice.

In aerobic organisms, the use of oxygen (O(2)) to produce energy is associated with the production of Reactive Oxygen Species (ROS), which reacts with biological molecules to produce oxidized metabolites such as malondialdehyde (MDA). This experiment focused on male Swiss mice 12 weeks of age synchronized for 3 weeks by the 12 h light (rest)/12 h dark (activity) span. Different and comparable groups of animals (n=10) were sacrificed at six different circadian stages: 1, 5, 9, 13, 17, and 21 h after light onset (HALO). The 24 h mean MDA level varied among organs of mice in non-stress conditions and was comparable in brain and liver but lower than in kidney. As the MDA 24 h status constitutes only a part of ROS damages in sites differing by their oxygen use, lipid composition, and detoxification capacity, the temporal patterns of their MDA content were comparatively studied in relationship to the animal rest-activity cycle. The results revealed significant circadian rhythms with the peak time located during the rest span (approximately =5 HALO) for both brain and liver, but during the activity span for the kidney ( approximately =21 HALO) and plasma (approximately =13 HALO). This chronobiological study showed that under physiological conditions, lipid peroxidation depends on several factors. The MDA peak/trough might be used as a tool to detect moments of high/low sensitivity of tissues to ROS attack in rodents.