Circadian changes in ATP-ase Mg activity and in Mg and Ca content of rat liver in relation to age and season

This experiment was carried out on male Wistar rats aged 6, 12, and 24 months in two seasons, autumn and winter. In all age groups, the activity of Mg-dependent ATP-ase (Mg2+ -ATPase) showed rhythmic oscillations with a 12-hour period. A similar time course was observed for 12-hour variations in Mg and Ca concentrations. In both seasons the maxima of ATP-ase Mg activity paralleled the maxima of Mg and Ca concentrations. When two maxima were observed, one of them always occurred in the light phase and the other in the dark phase of the 24-hour LDcycle.