Prolactin bioactivity following decidual synthesis and transport by amniochorion

Cabergoline Failure and a Spontaneous Pregnancy in a Microprolactinoma with High Prolactin Levels

We report a particular case of a spontaneously occurring pregnancy in a long-term amenorrheic patient due to a prolactinoma with high serum prolactin (PRL) following the failure of dopamine agonist therapy (DA) for infertility. Initially, clinical, laboratory, and genital ultrasounds were normal, but the serum PRL was 10,074 μIU/mL (n.v.: 127−637 μIU/mL), the PEG fraction was 71% (laboratory cut-off > 60%), and luteinizing hormone (LH) was significantly lower. An MRI revealed a pituitary tumor of 12.8/10 mm with a subacute intratumoral hemorrhage. DA was initiated, and menstrual bleeding reappeared with a reduction in the tumor’s volume to 1.9/2.2 mm at 12 months. Two years later, the patient renounced DA and follow-ups. After another 2 years, she became spontaneously pregnant. Serum PRL was 18,325 μIU/mL, and an MRI revealed a microprolactinoma of 2.1/2 mm. The patient gave birth to a normal baby at term, and she breastfed for six months, after which she asked for ablactation, and DA was administered. This case highlights the possibility of the occurrence of a normal pregnancy during a long period of amenorrhea induced by a microprolactinoma with a high level of serum PRL, even if DA fails to correct infertility. There was no compulsory relationship between the tumoral volume’s evolution and the evolution of its lactophore activity. The hypogonadotrophic hypogonadism induced by high PRL was mainly manifested by low LH, and in this situation, normal levels of FSH and estradiol do not always induce follicle recruitment and development without abnormalities in the ovary ultrasound.

Expression of aquaporin 8 and its up-regulation by cyclic adenosine monophosphate in human WISH cells

OBJECTIVE

Water absorption across the fetal chorioamniotic membranes is a critical regulatory pathway for amniotic fluid volume homeostasis. Aquaporins are cell membrane proteins that significantly enhance membrane permeability to water by acting as water channels. We recently demonstrated that aquaporin 8 is expressed in human amnion, chorion, and placenta. Thus, aquaporin 8 expression represents a molecular mechanism of amniotic water absorption through intramembranous pathways. The current study sought to determine whether aquaporin 8 is expressed in human amnion-derived cell culture and to explore its regulation by second messenger cyclic adenosine monophosphate.

STUDY DESIGN

Human amnion-derived WISH cells were cultured. Total RNA was isolated and reverse transcriptase-polymerase chain reaction was used to determine aquaporin 8 gene expression. To determine the effect of cyclic adenosine monophosphate on aquaporin 8 expression, WISH cells were cultured in the presence of either monobutyryl cyclic adenosine monophosphate or the cyclic adenosine monophosphate-elevating agent forskolin. Multiplex semiquantitative reverse transcriptase-polymerase chain reaction was carried out to quantify aquaporin 8 messenger RNA levels.

RESULTS

Reverse transcriptase-polymerase chain reaction detected aquaporin 8 expression in WISH cells. After forskolin treatment for 2 hours, aquaporin 8 messenger RNA expression in WISH cells increased 4-fold (P <.001). Stimulation of aquaporin 8 gene expression by colforsin was observed throughout the study period of 20 hours. Incubation of WISH cells with monobutyryl cyclic adenosine monophosphate resulted in a 2-fold increase in aquaporin 8 messenger RNA level (P <.001). However, stimulation of aquaporin 8 gene expression by monobutyryl cyclic adenosine monophosphate attenuated to baseline level after 20 hours of monobutyryl cyclic adenosine monophosphate treatment.

CONCLUSION

The current study demonstrates the expression of aquaporin 8 water channel in human amnion-derived WISH cells and aquaporin 8 expression up-regulation by second messenger cyclic adenosine monophosphate. Aquaporin 8 messenger RNA demonstrates a relatively short biologic half-life in vitro, which renders its rapid responsiveness to regulation

Diurnal changes in plasma prolactin during the last one third of pregnancy in the baboon

Previous studies in our laboratory revealed that daily plasma prolactin (Prl) levels were higher in the evening than in the morning in the pregnant baboon suggesting a diurnal variation. The goal of this study was to examine in more detail the diurnal alterations in plasma Prl levels. A tethered pregnant baboon model was utilized for these studies. Hourly venous blood samples were taken from 0700 to 2400 hr (n=10) or until 0700 hr the following day (n=5). The studies were performed at various days of pregnancy from day 135 until delivery. Plasma samples were analyzed for Prl by radioimmunoassay. A surge in plasma Prl was detected, starting around 1500 to 1600 hr and lasting for 3 to 5 hr. The surge occurred before the lights went off in the colony (1800 hr). Baseline Prl levels were higher in animals < 15 days before delivery compared to those > 15 days before delivery (P < 0.05). In contrast, no differences were found in the average peak Prl values between these two groups of animals. In summary, in the pregnant baboon during the last one-third of pregnancy plasma Prl surges, beginning around 1500 to 1600 hr and lasting for 3 to 5 hr. Less than 15 days before delivery the mean baseline Prl levels are higher compared to animals greater than 15 days before delivery.

Permeability of human placenta and fetal membranes to thyrotropin-stimulating hormone in vitro

We determined the placental transfer of TSH in an in vitro model of dually perfused isolated lobule in 28 human term placentas by adding varying concentrations (5-60 microIU mL(-1)) of TSH as a single bolus dose to the closed maternal circulation. Transmembrane transfer of TSH was also studied by adding 45 microIU mL(-1) to the maternal or fetal compartment of a dual chamber of fetal membranes in culture. Passage of freely diffusible markers creatinine and antipyrine were also studied in this model. TSH concentration was measured by third generation chemiluminescence assay with a sensitivity of 10 mIU mL(-1). In the perfusion experiments, at physiologic concentrations the slow decline of TSH in the maternal circulation was associated with a small linear increase in fetal levels to 0.11 +/- 0.04% of initial dose at 2 h. The placental transfer rate was 0.08 microIU min(-1). Increasing maternal concentrations of TSH were associated with proportional increases in transfer rate (y = 0.002x; R2 = 0.99) and placental uptake (y = 0.01x; R2 = 0.97). The placental permeability of TSH was 2.4 x 10(-4) mL min(-1) g(-1) and was proportional to its coefficients of diffusion in water and molecular size. The transmembrane transfer and permeability of TSH was comparable to those of the placenta. We conclude that TSH crosses the human term placenta and fetal membranes sparingly.

Milk-borne prolactin and neonatal development

Milk is primarily regarded as a food furnishing essential nutrients for infant growth and development, but milk can also serve as a vehicle for mother to neonate transfer of molecules that regulate development. A wide array of biologically active compounds such as hormones, cytokines and enzymes are present in milk, especially early milk. The premise that prolactin (PRL) in milk is an important and possibly essential developmental factor for the newborn is explored. Both PRL and structurally modified isoforms are abundant in early milk and gradually diminish with the progression of lactation. Milk PRL is absorbed and biologically active in the neonate. Assays of PRL variants, experimental paradigms to test them as developmental regulators and the body of evidence supporting the hypothesis that milk PRL regulates differentiation and maturation of neonatal neuroendocrine, reproductive, and immune systems is presented.

Cervicovaginal prolactin: a marker for spontaneous preterm delivery

OBJECTIVE

Our purpose was to determine whether the presence of prolactin in cervicovaginal washings is associated with preterm birth.

STUDY DESIGN

A cohort of 80 patients underwent a washing of the ectocervix and vaginal fornices with a normal saline solution. The cohort consisted of two groups: 40 inpatients requiring tocolysis and 40 asymptomatic outpatients. The saline solution aspirates were centrifuged, the supernatant was stored at -70 degrees C, and a radioimmunoassay for prolactin was run in batch fashion. A prolactin concentration greater than the detection limit of the assay was considered a positive test result.

RESULTS

Prolactin was identified in significantly more symptomatic patients than asymptomatic controls (50% vs 5%, p < 0.0001). In symptomatic patients cervicovaginal prolactin had an 80% positive predictive value and a 65% negative predictive value for delivery at < or = 34 weeks' gestation. Patients testing positive for prolactin had significantly shorter latency from testing to delivery (16 +/- 17 vs 34 +/- 24 days, p = 0.02) and had significantly lower birth weights (1985 +/- 729 vs 2583 +/- 696 gm, p = 0.01) compared with patients testing negative. Prolactin was also identified in two asymptomatic patients, both of whom were delivered before term.

CONCLUSIONS

Cervicovaginal prolactin is a biochemical marker for preterm delivery, a shorter latency period to delivery, and lower birth weight in symptomatic patients. This test may also prove to be a valuable marker for preterm birth in asymptomatic women.

Dynamics of prolactin in amniotic fluid and extraembryonic coelomic fluid in early human pregnancy

Concentrations of prolactin were measured by an immunoradiometric assay in 26 matched samples of amniotic fluid, extraembryonic coelomic fluid and maternal serum from 9 to 12 weeks of pregnancy and in a further 131 amniotic fluid samples from 9 to 20 weeks. Low levels of prolactin (median 40 MU/l) were present in amniotic fluid from 9 to 12 weeks. Levels in the coelomic fluid were higher (median level 371 MU/l; P < 0.0001) than in amniotic fluid. From 13 weeks, there was a rapid rise in amniotic fluid prolactin to reach a peak at 19 weeks (median level 99,850 MU/l). The pattern of increase of prolactin in amniotic fluid is similar to, but occurs 2 weeks later than that for insulin-like growth factor-binding protein-1, another major decidual product.

Comparisons of glycosylated and nonglycosylated amniotic fluid prolactins in normal second- and third-trimester pregnancies

Prolactins in glycosylated and nonglycosylated form were isolated from 218 second- and third-trimester amniotic fluid samples by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electrotransferred to nitrocellulose paper, and probed with anti-human prolactin serum and protein A labeled with iodine 125. The glycosylated and nonglycosylated prolactin bands were exposed by autoradiography. The bands were analyzed by densitometry, and the ratio of glycosylated to total (glycosylated + nonglycosylated) prolactin was calculated (glycosylated/total ratio) and compared with matched prolactin radioimmunoassay measurements. Both radioimmunoassay-measured and nonglycosylated prolactin decreased from the second to the third trimester whereas glycosylated prolactin concentrations remained unchanged. Concomitantly, glycosylated/total prolactin ratios increased significantly (p less than 0.001). The correlation of radioimmunoassay-measured prolactin was closer to nonglycosylated prolactin (r2 = 0.32, p = 0.00001) than to glycosylated prolactin (r2 = 0.02, p = 0.06). We suggest that the proportion of amniotic fluid glycosylated prolactin increases with length of gestation and that glycosylation of prolactin is inversely related to total prolactin secretion. Furthermore, prolactin's immunoreactivity correlated more closely to the nonglycosylated-prolactin variant, suggesting that radioimmunoassay of prolactin poorly recognizes the glycosylated prolactin form.

Fetal control of maternal prolactin production and bioactivity in utero

Amniotic fluid prolactin is a product of maternal decidualized endometrium that is derived by translocation of the hormone across the reflected fetal membranes. Amniotic fluids from 26 second-trimester (14 to 23 weeks) and 75 third-trimester (29 to 40 weeks) normal singleton pregnancies were evaluated for prolactin content by radioimmunoassay and bioassay with the Nb2 rat lymphoma cell line. The relative bioactivity was calculated as the ratio of bioassay to radioimmunoassay for each fluid. Data segregated by gestational age and fetal genetic sex identified a highly significant difference (p = 0.0004) in amniotic fluid prolactin radioimmunoassay concentrations (mean +/- SEM) that surround male (682 +/- 49, n = 42) versus female (440 +/- 39, n = 33) fetuses of third-trimester age. Paired bioassay values were significantly lower (p = 0.002) than radioimmunoassay values among males (626 +/- 52) but equivalent (p = 0.1066) among females (464 +/- 44). The bioassay/radioimmunoassay ratios of third-trimester fetal female-associated amniotic fluid prolactin were significantly higher (p = 0.0004) than those of third-trimester males and second-trimester males and females. The results suggest a fetal gender-related factor is associated with both the production and the biologic activity of the maternally derived hormone. Thus the fetus appears to have some control over the dynamics of uterine prolactin production.

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 less than 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.

Fluid transport across human fetal membranes affected by human amniotic fluid prolactin: an in vitro study

The aim of the study was to investigate the effects of human amniotic fluid (AF) prolactin (PRL) on the transfer of fluids across human fetal membranes, detected in vitro by weight change. We have developed a system, consisting of an inner compartment (4 ml), suspended in an outer compartment (40 ml), and separated from it by a 2 cm2 circular piece of fresh human fetal membrane (amnion, chorion and adhering decidua). The weight of the inner compartment was continuously registered with an electronic precision balance. Osmolality changes or hydrostatic pressure differences did not affect the rate of mass transfer through the membranes. Potassium cyanide significantly influenced the mass transfer in favour of the applied hydrostatic pressure difference (+2 cm H2O to the amniotic side) or osmotic pressure difference (amniotic side 265 mosm/kg/decidual side 285 mosm/kg). The PRL preparations used were human and ovine pituitary PRL, as well as three fractions isolated from human AF by fractionated ammonium sulphate and ethanol precipitations, followed by Sephacryl chromatography. All PRL preparations were tested in physiologic concentrations (0.5 to 5 micrograms/ml). Only the two largest AF-PRL variants significantly disturbed the balance of fluid transfer across the membranes when added to the fetal (amniotic) side of the membrane. This resulted in a net increase in fetomaternal transfer of 120 to 180 microliters. This effect could be repeated and lasted for at least 25 minutes. Using an antibody against hPRL the effect was completely blocked. Neither AF-PRL added to the maternal (decidual) side of the membrane nor oPRL or human pituitary PRL added to the amniotic or decidual side changed the rate of mass transfer across the membranes.

Effect of short-duration progesterone treatment on decidual prolactin production by cultures of proliferative human endometrium

The effect of short-term progesterone (P) treatment in vitro on decidual prolactin (dPRL) production by human endometrium was investigated. Cultures prepared from proliferative endometrium received medium containing P for 3 hours, 1 day, or 3 days. The culture medium was then changed daily for 7 to 14 days, and the amounts of dPRL in the spent medium were measured by radioimmunoassay. The results of these experiments indicated that even a short exposure to elevated concentrations of P is adequate to stimulate dPRL production and that the resulting pattern of dPRL production is determined by the duration of the P treatment.

Amniotic fluid prolactin, decidual prolactin content and decidual prolactin secretion into hypo-, iso-, and sodium chloride hyperosmotic media in vitro in pregnant diabetics at term

This study evaluated in pregnant women with diabetes mellitus (DM) the prolactin (PRL) concentration in amniotic fluid (A-PRL), the initial decidual PRL content (D-PRL), and the decidual PRL secretion (D-PRL-s) in vitro into isosmotic (315 mmol/kg), hyperosmotic (426 mmol/kg) and hyposmotic (252 mmol/kg) media. Decidual tissue was collected at term from 18 normal pregnancies and from 23 women with DM (White's classification: 7 of class A (without insulin treatment) and 16 of the classes B-F. Twelve of the women with DM had signs of hydramnion. Amniotic fluid specimens were collected from 52 normal pregnancies and 17 of the women with DM. No significant difference was found between normals and diabetics when D-PRL, D-PRL-s into isosmotic medium and A-PRL were compared. No trends could be detected when the insulin treated women were grouped according to White's classification. The increment of D-PRL-s into hyperosmotic medium was 15% in normals (p less than 0.001 compared with isosmotic medium), in the DM group 23% for the non-insulin-treated women (p less than 0.05 when compared with normals) and 25% for the insulin treated women (p less than 0.01). In normals the hyposmotic medium reduced D-PRL-s by secretion 19% (p less than 0.001 compared with isosmotic medium) but no significant difference was observed between normals and diabetic groups (p greater than 0.10). In the group of diabetics no significant difference was found in any of the PRL quantities investigated between those with and without hydramnion.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of short-loop inhibition of decidual prolactin synthesis by decidual proteins. Part I

Induction of uterine endometrial prolactin synthesis is dependent on progesterone-induced decidualization of stromal cells. These decidual cells are not dependent on progesterone for continued prolactin synthesis. The factors modifying decidual prolactin synthesis remain largely unknown. To test the hypothesis that a decidual protein is the major modulator of new prolactin synthesis, decidua were cultured within dialysis membranes allowing the accumulation of proteins greater than 12,000 molecular weight in a metabolically neutral environment, and the rate of new synthesis was compared with prolactin synthesis from samples cultured in 10 times the available volume for protein distribution. The rate of new prolactin synthesis at 48-hour intervals up to 144 hours was compared. Initial and postculture decidual prolactin content was obtained and was found not to vary significantly between groups (0.05 less than p less than 0.10). At 48 hours significant suppression of decidual prolactin synthesis was apparent (p less than 0.05) within the dialysis membranes. As prolactin concentration increased during in vitro culture this suppression was enhanced (p less than 0.005). Gel chromatography and immunoprecipitation of iodine 125-labeled prolactin added at time 0 revealed no significant degradation of the 125I-labeled prolactin and maintenance of its immunoactivity even at 144 hours. This confirms that the plateauing of prolactin concentration within the dialysis membranes is due to suppression of new synthesis rather than metabolism of previously synthesized prolactin.

Evidence of short-loop inhibition of decidual prolactin synthesis by decidual proteins. Part II

We have recently demonstrated the suppression of decidual prolactin synthesis by decidual proteins accumulating in a dialysis membrane. In this report the reversibility of this suppression and the molecular weight range of the suppressor(s) are examined. Samples of 300 mg of decidua (n = 10) were cultured in three environments: in 30 ml of medium (control), in 3 ml of medium in a dialysis membrane suspended in 27 ml of medium, and in 2.7 ml of medium with 0.3 ml of concentrated decidual proteins of 10,000 to 35,000 molecular weight (giving a time 0 prolactin concentration of 220 ng/ml) in a dialysis membrane suspended in 27 ml of medium (n = 5) or in 2.7 ml of medium with 0.3 ml of concentrated decidual proteins greater than 35,000 molecular weight (giving a time 0 prolactin concentration of 5 ng/ml) in a dialysis membrane suspended in 27 ml of medium (n = 5). Dialysis membranes were discontinued at 48, 96, and 144 hours and the decidua within was subsequently cultured in 30 ml of medium until 240 hours. The suppression of prolactin synthesis identified previously was confirmed in this study. Further it was found that the suppression of decidual prolactin synthesis was reversed by the removal of decidua from the high decidual protein-prolactin environments of the dialysis membranes. Third, only the addition of decidual proteins between 10,000 and 35,000 molecular weight with a high prolactin concentration enhanced the suppression of new prolactin synthesis. We conclude that a decidual protein(s) between 10,000 and 35,000 molecular weight, possibly prolactin itself, is the primary control factor(s) in the modulation of prolactin synthesis in term decidua. Further the normal physiologic state of decidua is a high prolactin concentration in equilibrium with low prolactin synthesis. Therefore studies intended to assess the effects of modulators of prolactin synthesis in decidua should not be performed in low prolactin concentration-high prolactin synthesis conditions during short time periods (as has been the case in a majority of studies to date) since such conditions do not reflect normal physiologic conditions and may result in invalid conclusions.