Development of fetal mineral and trace element metabolism in rats with normal as well as magnesium- and zinc-deficient diets

At d 17 of gestation, the concentrations of K, Mg, Mn, and Zn in fetal rat serum, measured by flame photometry and atomic absorption spectrophotometry, were higher than in maternal serum and declined thereafter. The serum concentrations of protein and Cu increased, whereas the Na concentration remained constant during perinatal development. In Mg and Zn deficiency, the concentrations of Mg and Zn in fetal serum were less reduced than in maternal serum. During perinatal development, the contents of K and Mg in fetal liver decreased continuously, whereas the contents of Zn and Cu transiently increased, reaching a peak at 1 and 7 d after birth. The decrease of Mg in fetal liver was caused by a reduction of Mg in the nuclei and microsomes. The transient increase of Zn content in fetal liver resulted from the induction of Zn-metallothionein, as determined by Sephadex G-75 gel filtration. Magnesium deficiency had no significant effect on Mg content of fetal and perinatal liver. In Zn deficiency, induction of Zn-metallothionein in fetal liver was delayed and reduced. Zinc content in fetal kidneys was not significantly changed by Zn deficiency.