Magnesium-induced hypocalcemia in salicylate-treated pregnant rats.

Pregnant and non pregnant rats were fed diets with different Mg content and treated with 5 oral doses of 300 mg/kg salicylic acid for 5 consecutive days or from day 16 to 20 of gestation. One day after the final dosage, serum Mg and Ca concentrations were measured by atomic absorption spectrophotometry. In maternal rats, salicylate caused a strong decrease of serum Ca with increasing serum Mg concentrations (r = -0.8706). In fetal and nonpregnant adult female rats, serum Ca was not significantly decreased by salicylate with increasing serum Mg concentrations. However, the hypocalcemic effect of salicylate was found when nonpregnant young growing rats were fed a Ca-deficient diet.