Assessment of fetal rat parathyroid gland activity during hypocalcemia induced by EDTA

Rat fetuses with or without parathyroid glands (intact or decapitated at 17.5 days of gestation) were injected subcutaneously with the disodium salt of EDTA at 21.5 days of gestation. In the two groups, the unchelated plasma calcium levels were measured within 180 min following the injection. The lowest plasma calcium values were observed 30 min after injection of EDTA in both groups of fetuses. In intact fetuses, the return of plasma calcium levels to normal was completed within 180 min. In decapitated fetuses, recovery was delayed. The marked difference in the recovery curves between the two groups establishes the role of the fetal parathyroid glands in controlling fetal hypocalcemia. Factors which may explain the high plasma calcium level in the rat fetus are discussed in relation to findings from previous reports.