Effect of endurance training on diurnal rhythms of superoxide dismutase activity, glutathione and lipid peroxidation in plasma of pinealectomized rats

Melatonin deficit is characterized by disturbed circadian rhythms of many physiological and biochemical parameters including markers of oxidative stress. Moderate endurance training exerts protection against oxidative stress. In the present study, we aimed to explore the impact of endurance treadmill training on disturbed rhythmic fluctuations of some markers of oxidative stress in pinealectomized rats. Animals were divided into four groups: sham-operated sedentary rats (sham-sed), a sham group with exercise (sham-ex), pinealectomized sedentary rats (pin-sed) and pin rats with exercise (pin-ex). Animals were sacrificed by decapitation at 4-h intervals for biochemical analysis of plasma melatonin and markers of oxidative stress. The activity of superoxide dismutase (SOD) and the levels of glutathione (GSH) and lipid peroxidation demonstrated diurnal variations in the sham-sed group. The peak values of SOD were detected during the dark period that coincided with the peak plasma levels of melatonin in the sham-sed rats. The malondialdehyde (MDA) levels also showed a tendency to a progressive raise during the dark period. Pinealectomy was characterized by a remarkable melatonin deficit in plasma of sedentary rats, compromised fluctuations with decreased SOD activity and increased lipid peroxidation. While endurance training was unable to restore the melatonin deficit, it partly prevented the oxidative stress at selected time points in the pinealectomised rats. Our findings indicate the important role of endurance training against oxidative stress both in physiological conditions and melatonin deficit.