Patterns of mid-to-term placental enzymes in rats treated with magnesium sulphate

1. Pregnant rats were injected daily with 150 mg/kg b.w. of magnesium sulphate (MgSO4) starting at the 5th day gestation and sacrificed at the 13th, 15th, 19th or the 21st day of pregnancy. 2. The profiles of LDH, G-6-PD, HK and Ala-T activities in mid-to-term placentae were not changed by the drug. 3. Placental PK was strongly activated by MgSO4 in 13-19 day pregnant rats, whereas Asp-T was more severely depressed at the final phase of pregnancy. 4. Although mild to moderate changes in the flow of substrates should be predictable by the results, it seems unlikely that these could account for the reported deleterious effects of MgSO4 on rat offsprings.