Levels of testosterone in plasma and concentrations of LH in both plasma and pituitary glands of fetal mice aged 14, 16 and 18 days were measured by radioimmunoassays in a representative number of fetuses. During this period levels of testosterone in the plasma of male mice were significantly higher than those in the females. Levels of testosterone in plasma of male mice increased from day 14 to day 16 of gestation and decreased on day 1 before parturition. Plasma concentrations of LH remained undetectable in male and female fetuses until day 16 of gestation. levels of LH rose slightly in both sexes in later gestation, but still remained significantly lower in the plasma of male fetuses on days 17-18. In contrast, higher but not significantly different concentrations of LH were observed in pituitary glands from days 14 to 18 in male compared with female mice. These observations suggest that the high levels of testosterone in the plasma of male fetal mice might be responsible for feedback inhibition of LH secretion during the last days of gestation.

The presence of receptors for GnRH in human ovary has been investigated by quantitative autoradiography. Simultaneous visualization and characterization of specific receptors on frozen sections were obtained on six pairs of human ovaries. Among them only one exhibited a large preovulatory follicle. This dominant follicle exhibited a specific and high affinity binding capacity for 125I-GnRHa exclusively localized on the granulosa cell layer. Analysis of saturation curve indicates a Kd value of 0.22 nM and Bmax of 9.6 fmol/mg protein. In contrast LH-hCG binding sites were present in all antral follicles. These data demonstrate for the first time the presence of high affinity GnRH receptors in human granulosa cells at a late stage of follicular maturation.

SummaryOxygen consumption, glucose transfer and utilization, and lactate and ammonia release were studied in the human full term placenta using an in vitro perfusion technique. DGlucose was the only substrate added to the perfusion fluid. On the maternal side, oxygen and glucose were taken up at a constant rate during perfusion. On the fetal side, a lower oxygen uptake was observed. Glucose was steadily released into the fetal perfusate as a result of the downhill concentration gradient established between maternal and fetal circulations. Bv contrast. lactate and ammonia release took place only into thematernal circulation and decreased rapidly during perfusion. No significant change in tissue glucose content was observed between the onset i d the endof the experiment. Placental lactate and ammonia concentrations were shown to diminish significantly during perfusion. Abbreviation v-a, veno-arterialThe supply of oxygen, glucose, and amino acids to the fetus has often been studied without due regard to their rate of metabolism in the placenta. There are now several lines of evidence indicating that placental metabolism interferes with the transfer of certain endogenous molecules. During transfer across the perfused human placental lobule, an extensive conversion of cortisol to cortisone has been demonstrated (4). Furthermore the lack of glutamate transfer has been interpreted as being the result of its rapid uptake and degradation by the trophoblastic membrane (19).The role of placental metabolism in relation to the supply of glucose and lactate to the fetus was studied recently in sheep. Placental tissue utilization of glucose seems to be implicated in the limitation of its materno-fetal transfer (22). Maternal lactate is transferred only in small amounts across the sheep cotyledon(l1); however, this substrate is produced by the placenta and release into the umbilical circulation (1, 23).The purpose of this study is to reexamine some aspects of transfer and metabolism in the perfused human placenta using only D-glucose as substrate. Oxygen consumption, glucose transfer and utilization, lactate and ammonia release were investigated to serve as a baseline for further studies with additional substrates. MATERIALS AND METHODSPefusion technique. Human placentae from uncomplicated pregnancies were collected after vaginal delivery at term. The perfusion technique has been described in detail by Schneider et al. (18). A suitable lobule was selected for perfusion. The fetal vessels were canulated with polyethylene catheters. Two fine canulas were inserted directly into the intervillous space over the area blenched by perfusion of fetal circulation. The maternal outflow, emerging from openings in the decidual plate, was drained outside the perfusion chamber. The perfusion was started within 30 min after delivery. Fifteen minutes were allowed to wash out the blood from the circulations, after which the experiment lasted 45 min.To allow for metabolic studies, changes in temperature control were introduced into the orieinal d...