Daily magnesium supplementation on serum and urinary magnesium changes in rats during prolonged restriction of motor activity

The objective of this investigation was to determine whether a plentiful magnesium (Mg²⁺) supplementation might be used to normalize or prevent Mg deficiency. This is manifested by increased rather than decreased serum Mg²⁺ concentration as is observed during prolonged hospitalization, which is developed during prolonged hypokinesia (HK) (decreased motor activity). Eighty male Wistar rats with an initial body weight of 370–390 g were used to perform the studies: They were equally divided into four groups:

1. Unsupplemented control animals (UCA);
2. Supplemented control animals (SCA);
3. Unsupplemented hypokinetic animals (UHA); and
4. Supplemented hypokinetic animals (SHA).

For the simulation of the hypokinetic effect, the hypokinetic animals were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The control and hypokinetic supplemental animals receive 0.9 mg/mL Mg sulfate daily with their drinking water. Prior to and during the experimental period, urinary excretions of Mg, calcium, and phosphate along with their concentrations in serum, water intake, and urine excretion, and body weight were determined in the control and hypokinetic animals. In the supplemental and unsupplemental hypokinetic rats, urinary excretions and serum concentrations of electrolytes increased significantly, whereas serum concentration and urinary excretion thereof remained unchanged in the supplemented and unsupplemented control animals. It was concluded that a daily intake of large amounts of Mg supplementation cannot be used to prevent or normalize Mg deficiency in rats during prolonged exposure to HK.