[Effects of dietary magnesium deficiency in the rat: with special reference to ultrastructural examination]

Epidemiologically, it has been suggested that dietary magnesium/calcium imbalance is associated with the risk of heart diseases. In the present study, the effects of magnesium deficiency and/or calcium over intake were investigated in rats. Male Sprague-Dawley rats were divided into 4 groups, and respectively fed basal diet (AIN-76) alone (Group 1), calcium-doubled AIN-76 diet (Group 2), magnesium-deficient AIN -76 diet (Group 3) and magnesium-deficient/calcium-doubled AIN-76 diet (Group 4) for 19 days. A biochemical assay using inductively coupled plasma showed that the magnesium concentrations of the femoral bone and serum were significantly (p < 0.001) lower in Groups 3 and 4 than in Group 1. The lipid peroxides of the heart in Group 4 and of the liver in Groups 3 and 4 were increased as compared to the Group 1 values although there was no statistical significance. Ultrastructurally, degenerative changes of organellas including mitochondria were observed in myocardial, liver and renal tubule cells of Groups 2-4. Severe degeneration such as disorganization, lysis and disarrangement of myofibrils was most evident in myocardial cells of Group 4. Our results thus suggest that dietary magnesium deficiency gives rise to retrogressive changes in some organs including the heart, and concurrent calcium overintake synergistically enhances the myocardial injury due to magnesium deficiency.