Hypocalcemic effect of zinc and mechanism in rats

The effect of zinc on serum calcium was investigated after a single oral administration of zinc sulfate in rats. Zinc (5, 10, and 20 mg Zn/100 g body weight) administration produced a significant decrease of serum calcium. This effect of zinc was not inhibited by thyroparathyroidectomy. Zinc administration resulted in a significant increase in calcium content of lungs and muscle but it was not significant in liver, kidneys, spleen and heart. Intestinal calcium absorption and bile calcium excretion was not affected by zinc administration. However, the urinary calcium excretion after zinc administration decreased markedly. On the other hand, zinc administration caused a remarkable elevation of calcium content in gastric secretion. This effect was dose-dependent (5 and 10 mg Zn/100 g). However, an increase in gastric calcium after zinc administration was completely prevented by atropine (0.1 micrograms/100 g) treatment, which also showed a marked inhibition of hypocalcemic effect of zinc. Meanwhile, acetylcholine (4.0 micrograms/100 g) administration caused a significant decrease of serum calcium by zinc administration is mainly based on an increase in gastric calcium secretion.