Effect of magnesium supplementation and training on magnesium tissue distribution in rats

The aim of this work is to study the effect of training and Mg supplementation on body pools of Mg and on Mg tissue distribution. Forty male Wistar rats were divided into four groups (n = 10): control group (C); trained group (T); Mg-supplemented group (+Mg); and trained and Mg-supplemented group (+MgT). The Mg supplement (1000 ppm of Mg) was given in the drinking water for 21 d. The training consisted of swimming during 60% of maximal swimming time obtained in the first session to exhaustion, during 3 wk (5 d a week). The variables measured were: erythrocytes (RBC), hemoglobin (Hb), hematocrit (Hto), total proteins (TP), and Mg in serum, RBC, liver, muscle, bone, and kidney. There was less Mg in liver, muscle, and erythrocyte in trained animals than in control or supplemented animals (T vs C, +MgT vs C and +MgT vs +Mg) (p < 0.01). Trained animals (T and +MgT) showed higher Mg kidney rates than the untrained ones (p < 0.01). There was less bone Mg in control (C) and in supplemented and trained (+MgT) groups than in trained (T) and in supplemented (+Mg) animals (p < 0.01). Serum Mg showed a decreasing concentration profile in the following order: +Mg, +MgT, T, C (p < 0.01). We conclude that Mg supplementation improves bone and serum Mg levels, but this does not affect Mg status in soft tissues. Maintained exercise leads to a diminution of Mg in the aforementioned soft tissues that is not noticeable in serum, probably provoked by an increase of renal excretion.