Effects of desoxycorticosterone acetate on magnesium metabolism in potassium-depleted rats

Metabolic balance studies were performed in two groups of 6 rats each, pair-fed a diet deficient in potassium. While one group was injected with desoxycorticosterone acetate (DOCA) for 11 days, the other group, used as a control, was injected with oil. The administration of DOCA suppressed or reversed the thirst, natriuresis, diuresis, calciuria and magnesiuria that developed in the potassium-deficient control group. Potassium-depleted DOCA-treated rats had a more positive water and sodium balance, experienced a significant expansion in plasma volume, had a more negative potassium balance and had a lower plasma potassium concentration. Magnesium balance decreased in the group fed the diet deficient in potassium and injected with oil but it rose towards control levels in the group fed the same diet and treated with DOCA. As the content of potassium in muscle decreased in rats fed the diet deficient in potassium and injected with oil, the concentration of magnesium in muscle also fell and the plasma concentration of magnesium increased. Thus, the hypermagnesemia of potassium depletion could be explained by the shifting of magnesium from tissue into the extracellular space. The partial compensation of the hypermagnesemia observed in the potassium-deficient group injected with DOCA may be the result of the hemodilution secondary to plasma expansion.