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Parathyroid hormone-related (PTHrP), the major mediator of humoral hypercalcemia of malignancy, may also regulate placental calcium flux, uterine contraction and fetal tissue development. In the present study, we demonstrated that the mean immunoreactive PTHrP concentrations in amniotic fluid at mid-gestation (21.2 +/- 3.7 pmol/l) and at term (19.0 +/- 2.7 pmol/l) were 13-16-fold higher than levels measured in either fetal (1.6 +/- 0.1 pmol/l) or maternal plasma (1.4 +/- 0.3 pmol/l) at term and equal to levels found in plasma of patients with humoral hypercalcemia of malignancy. In vitro studies pointed to three possible sources of PTHrP in amniotic fluid: cultured amniotic fluid cells, cells derived from the amniotic membrane overlying the placenta and placental villous core mesenchymal cells. Treatment of cultured amniotic fluid cells with human prolactin, human placental lactogen (hPL) or human growth hormone (100 micrograms/l) increased PTHrP secretion after 24 h by 43%, 109% and 90%, respectively. Insulin-like growth factors I and II (100 micrograms/l), insulin (100 micrograms/l) and epidermal growth factor (EGF) (10 micrograms/l) increased PTHrP secretion by 53%, 46%, 68% and 118%, respectively. The stimulation of PTHrP secretion by EGF or by hPL was both time- and dose-dependent. In contrast, calcitriol and dexamethasone (10 nmol/l) decreased PTHrP secretion by 32% and 75%, respectively. Estradiol, progesterone, dihydrotestosterone and human chorionic gonadotropin had no effect on PTHrP secretion. These findings support the notion that PTHrP may play a physiological role in the uteroplacental unit and demonstrate that human amniotic fluid cells could be a useful model for studying the regulation of PTHrP production and secretion by hormones and growth factors.

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Four groups of pregnant mice were fed milled food containing 3 g/kg phenobarbital, acid, form, and water as their only nutritional source during various periods during pregnancy (days 9–18, 9–13, 13–16 or 16–18). Control females received milled food and water. The brains of control and phenobarbital-treated male offspring were removed at age 50 days, fixed, cut and stained with HE. Matching sagittal sections were selected for the study of the cerebellar Purkinje cells and the hippocampal pyramidal cells. Previous findings were confirmed in that prenatal phenobarbital exposure during the last two trimesters of pregnancy (days 9–18) resulted in a long-lasting deficit in the number of the Purkinje (23 %) and pyramidal cells 9% (P < 0.01). Phenobarbital administration during only part of this period (days 9–13, 13–16 or 16–18) had the same effect as administration during the entire period. The cell deficit did not correlate with the time of appearance of the neurons, thus, suggesting that phenobarbital may possibly act even on neurons which are already formed.