P. D. Gluckman

Fetal sex and prenatal betamethasone therapy.

We examined the influence of fetal sex on the occurrence of respiratory distress syndrome in premature infants after maternal treatment with betamethasone. Among treated infants of 1,251 to 1,750 gm birth weight, the incidence of RDS was 40.9% in 22 males and 7.1% (P = 0.03) in 14 females. Cord serum levels of betamethasone were similar for infants of both sexes, and there was no sex difference in suppression of serum cortisol, dehydroepiandrosterone sulfate, and growth hormone after treatment. These findings suggest that prenatal corticosteroid therapy is less effective in male infants than in female infants. This effect is not due to a difference in transfer or metabolism of betamethasone, nor is it reflected in the responsiveness of the fetal hypothalamic-pituitary-adrenal axis to synthetic glucocorticoid.

Failure to detect an effect of prolactin on pulmonary surfactant and adrenal steroids in fetal sheep and rabbits.

Recent reports have indicated an association between low cord prolactin (PRL) and the occurrence of respiratory distress syndrome in premature infants, and it is reported that PRL administration increases the lecithin content of fetal rabbit lung. We administered 1 mg ovine PRL to 32 rabbit fetuses on day 24 of gestation and evaluated lung phospholipid synthesis and content on day 26. Compared with diluent-injected littermates, PRL had no effect on the rate of choline incorporation into lecithin, tissue content of phospholipid and disaturated lecithin, or plasma corticoids. However, both choline incorporation and corticoids were increased in all animals undergoing surgery compared with unoperated controls. We also infused PRL (1 mg/day, i.v.) into three fetal sheep continuously over five periods of 5-8 days. Although supraphysiologic concentrations of PRL were achieved in plasma and amniotic fluid, there was no effect of this treatment on the flux of tracheal fluid surfactant or on plasma concentrations of corticoids of dehydroepiandrosterone sulfate. Thus, in this study, we failed to detect either a stimulation of the surfactant system or an adreno-corticotropic effect by PRL as previously postulated. This suggests that the relationship between PRL and respiratory distress sundrome is an indirect association.

Hormone ontogeny in the ovine fetus. IV. Serum somatomedin activity in the fetal and neonatal lamb and pregnant ewe: correlation with maternal and fetal growth hormone, prolactin, and chorionic somatomammotropin.

Summary: Somatomedin (SM) activity was measured by a placental membrane receptor assay using 125I-labeled somatomedin A, as radioligand in serum samples obtained from 33 ovine fetuses, 14 neonatal lambs, 8 pregnant, and 3 postpartum ewes. The mean serum concentration of SM activity in eight adult rams was 2.06 ± 0.12 U/ml. In fetal sheep, SM activity was detected at 66 days gestation (term 147 days), in the youngest fetus studied. Before 100 days of gestation, SM was lower (P < 0.001) in fetal sheep (1.08 ± 0.18 U/ml) than in adult rams. In fetuses between 101 and 125 days. SM rose (P < 0.001) to 2.64 ± 0.32 U/ml. In late gestation fetal serum SM fell but during the neonatal period it rose to 3.38 ± 0.3 U/ml, higher (P < 0.01) than that in adult rams. Serum SM activity in the pregnant ewe prior to 100 days was 1.01 ± 0.11 U/ml, increased (P < 0.05) to 1.75 ± 0.21 U/ml between 125 days and term, and rose further to 2.56 ± 0.32 U/ml in the postpartum period. Maternal concentrations of serum SM in late gestation were significantly less than in the fetus. Gel chromatog-raphy of fetal, maternal, and neonatal sera indicated that over 90% of SM activity circulated in high-molecular weight form. The rise in SM activity in fetal serum between 100 and 125 days parallels the rise in fetal growth hormone and prolactin concentrations; however, in maternal serum the increase in SM activity is associated with rising maternal chorionic somatomammotropin concentrations.Speculation: Somatomedin is present in fetal ovine serum and in late gestation may be generated mainly by fetal pituitary hormones. In contrast, somatomedin in the pregnant ewe appears to be regulated by chorionic somatomammotropin.

Effect of long-term bromocriptine infusion on plasma prolactin and ovine chorionic somatomammotropin in the pregnant ewe and fetal sheep

It has been shown in previous studies that the continuous infusion of bromocriptine (CB 154) into either the sheep fetus or pregnant ewe was followed by pronounced ultrastructural changes in the binucleate (BN) cells of the ovine chorionic epithelium, which are a likely source of ovine chorionic somatomammotropin (oCS). We have examined ovine fetal and maternal plasma prolactin (PRL) and oCS concentrations following intravascular CB 154 infusion separately into either the fetus (0.03 mg/hour) or ewe (0.2 mg/hour). The CB 154 infusions significantly depressed fetal and maternal plasma radioimmunoassayable PRL concentrations within 24 hours of the commencement of infusion. Maternal plasma radioimmunoassayable oCS concentration was significantly depressed during infusion of CB 154 to the ewe, but the infusion of CB 154 to the fetus did not lower fetal plasma radioimmunoassayable oCS concentration or affect the duration of gestation.

Alpha melanocyte stimulating hormone inhibits prolactin secretion in fetal and infant lambs

Abstract The intravenous administration of αMSH (25 μg/kg) to 11 lambs (3 to 29 days of age) suppressed plasma PRL by 15 minutes. The mean basal concentration was 15.3 ± 2.9 ng/ml and the mean nadir was 4.9 ± 0.8 ng/ml (p