Cu/Zn superoxide dismutase is differentially regulated in period gene-mutant mice

► Antioxidant defense systems are under the influence of circadian rhythms. ► We examined the regulation of SOD1 expression in circadian mutant mice and MEF cells. ► Differences in the level of SOD1 expression and enzyme activity are evidently found. ► There are changes in the rhythmicity and phase of the rhythm among mouse genotypes.