Eytan R. Barnea

Modulatory action of benzodiazepines on human term placental steroidogenesis in vitro

Peripheral benzodiazepine (BZ) binding sites (PBzS) were characterized on placental explant membranes. [3H]PK 11195, an isoquinoline carboxamide derivative, which is a ligand specific for PBzS, labeled these sites with an equilibrium dissociation constant of 2.1 nM; the maximal number of binding sites was 396 fmol/mg protein. The effect of various BZ ligands and PK 11195 on the secretion of progesterone (P4) and estradiol-17 beta (E2) from human term placental explants was studied. Exposure of placental explants to low doses (10(-8) M) of Ro 5-4864, a BZ ligand which binds with high affinity to PBzS, caused a significant (P less than 0.05) increase in the secretion of P4 and E2 into the media (2.4- and 1.4-fold, respectively). On the other hand, high doses (10(-5) M) of Ro 5-4864 caused a significant (P less than 0.05) decrease in the secretion of P4 and E2 into the media. Also, exposure of explants to diazepam (10(-7) M) and PK 11195 (10(-6) M) caused a significant increase in P4 and E2 secretion into the media. In contrast, clonazepam, a BZ ligand specific for the central-type receptors, had no effect on the secretion of either steroid. The combination of diazepam (10(-7) M) or Ro 5-4864 (10(-8) M) with PK 11195 (10(-6) M) did not enhance the stimulatory effects obtained with each agent alone. The effects exerted by Ro 5-4864, PK 11195, and diazepam may be mediated via PBzS.

Stress-related reproductive failure

Life is a stressful experience, especially in modern civilization. Stress affects a large spectrum of biological systems including the reproductive system. The modern definition of stress as coined by Seyle is rather complex. It may be caused by any or all of the following: (1) the environment, (2) the response of the individual, and (3) the interaction of the individuals perception of the environment with the response. In the present review we focus on the adverse effects exerted by stressful conditions upon endocrine and reproductive processes.

Human embryonic origin early pregnancy factor before and after implantation.

ABSTRACT: Early pregnancy factor (EPF) is a factor that has been shown to be involved in the maintenance of the fetal allograft in several mammalian species including man. In that capacity it serves as a link between fertilization and immunomodulation. In the present study we have investigated the secretion of EPF by the human conceptus before and after implantation using rosette inhibition antibody concentration (T11 monocllonal antibody). In isolated trophoblastic cells at gestational week 7–9 there was a significant secretion of EPF. For the first 8 days in culture, secretion was maximal; later, however, at days 13 and 21 these levels declined. Further the EPF content of human embryonal extracts was examined. In various organs, spinal cord, liver, and kidney, significant EPF activity was detected. In women undergoing in vitro fertilization/embryo transfer, a total of 52 preimplantational embryos were cultured for 36 hours. No significant EPF activity was detected in the surrounding media. Two of the 11 patients studied became pregnant during the same cycle after embryo transfer. In conclusion, the preimplantational origin of EPF is maternal, while that of the post‐implantational embryo is of embryonal origin.

Stimulatory effect of prolactin on human placental progesterone secretion at term in vitro: Possible inhibitory effect on oestradiol secretion

Maternal and fetal circulating prolactin (PRL) increases 10-fold compared with the non-pregnant state. We examined the effect of PRL upon placental steroidogenesis. It had a significant (P < 0.05) time-dependent stimulatory effect upon placental explants/P4 accumulation and secretion into the medium. The maximal stimulatory effect (two-fold) in dose-dependent experiments was found to be 200 ng/ml. The effect of PRL upon oestradiol secretion was mainly inhibitory. This inhibition was most pronounced at 200 ng/ml. In conclusion, placental steroid secretion is modulated by PRL. This effect occurs mainly at concentrations seen in the placenta at term, suggestive of its physiologic role.

Human embryo modulates placental function in the first trimester; Effects of neural tissues upon chorionic gonadotropin and progesterone secretion

We investigated the effect of embryonal neural and adrenal tissues (7-14 weeks gestational age) upon beta hCG secretion by homologous placental explants in static and dynamic cultures. In static co-culture significant inhibition by SC and brain was noted at 7-9 weeks. Similarly, in superfusion, using a novel co-chambering technique there was a significant reduction in the area under the curve but not peak frequency of spontaneous pulsatile beta hCG secretion. Incubations with neural tissues 11 weeks and above caused a stimulatory effect upon beta hCG secretion in both models. The effect of adrenal tissue in static cultures was different, namely slightly inhibitory at 7-9 weeks and inhibitory at 11 weeks and above. In superfusion, the effect of adrenal tissue was not significant. Extracted neural tissue 7-9 weeks incubated with placental explants exhibited inhibitory effects upon beta hCG secretion as well. Buffer-based extracts of neural tissues effect was more pronounced than alcohol-based extracts regarding beta hCG secretion. The effect of extracts was dose-dependent and effects were noted up until a 2000-fold dilution. In contrast, the buffer SC extract had no effect on progesterone (P) secretion while the alcohol extract effect was inhibitory at 7-9 weeks and stimulatory at greater than 11 weeks. Superfused explants pattern of beta hCG secretion was inhibited by one minute pulse of the SC buffer extract. In conclusion, the human neural tissue of embryonal origin may modulate placental hCG and P secretion during early pregnancy.

Secretion of human chorionic gonadotropin in superfused young placental tissue exposed to cadmium

The effect of various concentrations of cadmium (Cd) in levels ranging from 0.75 to 12 μg/ml medium, on the secretion of human chorionic gonadotropin (hCG) in first-trimester placental expiants, after 6 or 24 h incubation, employing both static and dynamic systems was examined. Later the unbound Cd was washed for 45 min with fresh medium devoid of Cd, followed by superfusion with the latter medium for 75 min, during which time samples were collected for hCG assay. For the superfusion experiments the parameters used for evaluating the hCG secretion pattern were: mean peak amplitude (MPA), pulse frequency (PF) and the area under the hCG secretion curve (AUC). The results indicate that in the dynamic system the hCG secretion increased significantly, and this increase was dose dependent. There was also a dose-related increase in mean total hCG secreted by the explants exposed to Cd. Maximal hCG secretion was observed after 24 h exposure of explants to 6 μg of the metal/ml. Both the MPA and AUC parameters showed a statistically significant increase for this dose level. At 12 μg/ml, the pulsatile secretion of hCG decreased, the value for the mean hCG secretion being comparable to that observed for 0.75 μg/ml. After 6 h incubation, however, there were no significant changes from the control, as judged by all of the above parameters. The levels of hCG secreted by the explants into the media in the static system were not significantly different from their respective controls, for both incubation periods and Cd levels. These results indicate that Cd may affect the normal placental function, as reflected in its hCG secretion pattern.

Aryl Hydrocarbon Hydroxylase Activity in the First-Trimester Human Placenta: Induction by Carcinogens and Chemoprotectors

The activity of aryl hydrocarbon hydroxylase (AHH) was measured in the placenta using radioenzymatic techniques and benzo(a)pyrene (BP) as substrate. The optimal assay conditions were defined, including cofactor dependence. The Km of BP to the enzyme was 2 microM and Vmax 0.02 nmol/min. When compared to the AHH activity at term (0.35 +/- 0.03; mean +/- SEM), 1st-trimester activity was significantly lower (0.18 +/- 0.05; p less than 0.05). However, in the rat liver the enzyme activity was even higher than that found at term. In order to determine whether the 1st-trimester placental AHH activity is sensitive to environmental exposures, explants were incubated with two classes of xenobiotics: carcinogens and chemoprotectors. The carcinogen BP at 50 microM caused a significant (2.7-fold; p less than 0.05) increase in the enzyme activity after an incubation period of 6 h. After an incubation period of 24 h, however, no effect was noted. In contrast, 50 microM 20-methylcholanthrene had no effect. The effect of chemoprotectors was also examined: at 25 microM, coumarin, 2-(3)-tert-butyl-4-hydroxy-anisole, and 1-phenylazo-2-naphthol significantly increased 1.7, 1.7-, and 1.8-fold, respectively, the enzyme activity after an incubation period of 24 h (p less than 0.05). In conclusion, AHH in the 1st-trimester placenta is sensitive to environmental exposures and is induced in vitro by both carcinogen and chemoprotectors.