Lithium effects on serum calcium, magnesium and phosphate, in rats

LiCl was injected daily to rats in a dose of 3 mmol/kg. The rats were, in different experiments, unoperated rats, parathyroidectomized rats and thyroparathyroidectomized rats. Serum concentrations of calcium, magnesium, and phosphate were measured 2 h after a lithium injection. Serum calcium was unaffected by lithium in unoperated and parathyroidectomized rats. In thyroparathyroidectomized rats lithium increased the serum calcium concentration. Serum magnesium was increased by lithium in all 3 groups of rats. Serum phosphate was slightly decreased by lithium in all 3 groups of rats. It is concluded that lithium increases both serum calcium and magnesium, but in the intact organism only a slight or no increase in serum calcium is seem after lithium due to physiological control mechanisms. After removal of the calcitonin producing C-cells in the thyroid gland the organism is unable to produce a fast decrease in serum calcium, and lithium is then able to increase the serum calcium concentration.