Effect of hypoxia on placental activin A,inhibin A and follistatin synthesis

Placental activin A and inhibin A output is increased in pre-eclampsia, a condition characterized by placental hypoxaemia, whereas follistatin secretion is unaltered. We investigated whether hypoxia was the basis for elevated placental activin A and inhibin A output. First trimester and term placental explants were grown in 5-6% dissolved O(2) (n=10/trimester) and 200 microM cobalt chloride (CoCl(2),n =6/trimester) to simulate environmental and cellular hypoxia respectively, for up to 72 h. Activin A, inhibin A and follistatin production were compared with control cultures grown in standard media at 20% O(2). In first trimester and term placenta, activin A output declined significantly under 5-6% O(2) (P=0.006 and 0.001 after 48 h respectively). Inhibin A declined significantly under 5-6% O(2), mainly in first trimester placenta (P=0.03, 24h). CoCl(2) significantly elevated activin A production in term placenta (P=0.003, 48 h), whereas inhibin A output was unaffected. Neither low O(2) or CoCl(2) altered follistatin output from first trimester or term placenta. These findings suggest that there may be novel O(2) sensing mechanism/s that down regulate activin A and inhibin A in the placenta and that low O(2) is not the mechanism behind increased placental inhibin A or activin A output in pre-eclampsia.     

Intrabursal administration of protein kinase or proteinase inhibitors: effects on ovulation in the rat.

OBJECTIVE: To test the hypothesis that inhibition of protein kinase (PK) activity or proteolysis inhibits ovulation. DESIGN: Rats were injected intrabursally with protein kinase (H9 or staurosporin) or proteinase (alpha 2-macroglobulin) inhibitors and oocyte release was evaluated. SETTING: Clinical Research Laboratory, Center for Reproductive Medicine, University of Kentucky Medical Center. PARTICIPANTS: Immature rats stimulated with pregnant mare serum gonadotropin. INTERVENTIONS: Staurosporin (1 or 10 microM), H9 (1 mM), alpha 2-macroglobulin (835 microIU of activity); or vehicle was injected into the right ovarian bursa. The left ovarian bursa remained intact. Animals immediately received human chorionic gonadotropin (hCG). MAIN OUTCOME MEASURES: Analysis of oocyte release and ovarian morphology. RESULTS: Oocyte release from the inhibitor-treated side decreased for the H9 group (8.1 +/- 1.9 fewer oocytes released, P less than 0.001) and the 10 microM staurosporin group (5.5 +/- 0.6, P less than 0.001). No change in oocyte release was observed in the 1 microM staurosporin, alpha 2-macroglobulin, or vehicle injected groups. Histologic examination of vehicle treated ovaries demonstrated numerous developing corpora lutea (CL; 20.5 +/- 2.1 CL/ovary) and a lack of preovulatory follicles. In contrast, ovaries treated with PK inhibitors contained unruptured preovulatory follicles coincident with fewer forming CL (11.5 +/- 3.5 CL/ovary). CONCLUSIONS: Inhibition of PK activity in vivo suppresses ovulation, demonstrating that protein phosphorylation plays an important intermediary role in the ovulatory process.     

Serum levels of activin A and inhibin A and the subsequent development of preeclampsia

OBJECTIVE: To determine whether serum levels of activin A and inhibin A are altered in patients before development of preeclampsia. METHODS: Blood samples were collected from patients during the second trimester of prenatal care. We identified patients who subsequently developed preeclampsia and matched them with patients who had no evidence of preeclampsia during their gestation. Matching criteria included gestational age at blood sampling, gestational age at delivery, and birth weight. Assays were then performed to assess the levels of activin A and inhibin A in the control and study groups. A power calculation determined that 12 patients who subsequently developed preeclampsia, if matched with controls in a 1:2 ratio, would allow the detection of differences in analyte levels that were 60% as large as those previously reported between patients already diagnosed with preeclampsia and matched controls. RESULTS: Twelve patients with preeclampsia were identified and matched with 24 controls. No differences in serum levels of activin A or inhibin A were detected between the two groups. Because of the significant overlap of analyte levels between the two groups, no cutpoint that would allow identification of patients destined to become preeclamptic could be determined. CONCLUSION: These data suggest that activin A and inhibin A cannot be used as markers for later development of preeclampsia in a low-risk population.     

Circulating levels of inhibin A, inhibin B and activin A in normal and intrauterine growth restricted (IUGR) fetuses

OBJECTIVE: To evaluate the relationships between circulating levels of inhibin A, inhibin B and activin A, and sex, gestational age and gonadotropins in normal and pathological fetuses. STUDY DESIGN: The study included 31 normal fetuses and 12 affected with intrauterine growth restriction (IUGR) of gestational age ranging 20-40 weeks. RESULTS: No gender difference in inhibin A and activin A levels were observed. Inhibin B levels were significantly higher in males than in females (P < 0.05). Fetuses with the highest levels of inhibin A and B were found in the IUGR group that also showed activin A levels significantly higher than normal. No correlations were observed between inhibin A, inhibin B, activin A and both gonadotropins. CONCLUSION: Plasma inhibin A, inhibin B and activin A are detectable in both genders during intrauterine life. The different gender pattern of inhibin B suggests that inhibin B may contribute to the assessment of the hypothalamic-pituitary-gonadal set-point at least in males.     

Serum inhibin A, inhibin B, pro-alphaC, and activin A levels in women with idiopathic premature ovarian failure

Serum inhibin A, inhibin B, pro-alphaC, and activin A levels in 30 women with idiopathic premature ovarian failure (POF), 30 postmenopausal women, and 30 age-matched fertile women were determined. Women with POF showed low levels of inhibin A and inhibin B, but not of activin A, whereas the levels of pro-alphaC were significantly higher than in postmenopausal women. Thus, the circulating level of pro-alphaC could be a marker for assessing residual ovarian function in women with POF.     

Evidence for local production of inhibin A and activin A in patients with ovarian endometriosis

OBJECTIVE: To evaluate the expression of inhibin A and activin A in ovarian endometriosis. DESIGN: Uncontrolled cross-sectional study and controlled prospective in vitro study. SETTING: Academic health centers in Siena, Udine, Sassari, and Milan, Italy. PATIENT(S): A group of women (n = 19) who underwent laparoscopic excision of ovarian endometriotic cysts. INTERVENTION(S): Specimens of serum, peritoneal fluid, and cystic fluid, ovarian tissue for immunohistochemistry, and endometriotic cells for primary culture were collected. Cell cultures were also prepared from proliferative endometrium of women without endometriosis. MAIN OUTCOME MEASURES: Dimeric inhibin A and activin A concentrations in biological fluids; immunostaining of alpha and betaA subunits in ovarian endometrioma; alpha and betaA gene expression in cultured endometriotic cells compared with normal endometrium. RESULT(S): Inhibin A and activin A concentrations in the cystic fluid were slightly higher than in peritoneal fluid and significantly higher than in serum (P<.05). Immunoreactive alpha and betaA subunits were strongly expressed both in the epithelial and stromal components of ovarian endometrioma. The relative abundance of betaA mRNA was significantly decreased in endometriotic cells compared with eutopic stromal cells. CONCLUSION(S): The results of the present study provide evidence for a local production and secretion of inhibin A and activin A in ovarian endometriotic cysts.     

Decreased inhibin tone and increased activin A secretion characterize reproductive aging in women

OBJECTIVE: We hypothesized that the increased FSH noted in older reproductive-aged women is due to both decreased inhibin and increased activin A secretion. DESIGN: Comparative clinical study. SETTING: An academic research center. PATIENT(S): Five cycling women, aged 43 to 47, were compared to five midreproductive women, aged 19 to 38. INTERVENTION(S): Specimens taken every 2 to 3 days were assayed for inhibin A and B and activin A. MAIN OUTCOME MEASURE(S): Integrated concentrations of inhibin A, inhibin B, and activin A in the follicular phase, luteal phase, and whole cycle. RESULT(S): Follicular inhibin B was reduced in older versus younger women (504 +/-82 versus 748+/-72 total pg). Luteal inhibin A was reduced in older versus younger women (668 +/-72 versus 1152+/-216 total pg). Activin A was elevated throughout the cycle of older versus younger women, without within-cycle fluctuations (21+/-2 versus 11+/-1 total ng). CONCLUSION(S): Lack of restraint by inhibin A and inhibin B contributes to the FSH rise associated with reproductive aging. This loss of restraint occurs in a tandem fashion, with inhibin B reduction before ovulation and inhibin A reduction after ovulation. Activin A may also play an endocrine role in maintaining elevated FSH in older reproductive-aged women.     

Inhibin A,inhibin B and activin A concentrations in umbilical cord artery and vein

Activin A and inhibins (A and B) are growth factors expressed during pregnancy by the human placenta ,decidua and fetal membranes ,and by several fetal organs. They are secreted in both the maternal and the fetal circulations ,but the net contribution of the fetus to inhibins/activin A production is still unclear. In the present study we determined whether there was a difference in the serum concentration of activin A ,inhibin A and inhibin B between the artery and vein of the umbilical cord. Arterial and venous umbilical cord blood was obtained immediately before elective Cesarean section of 16 term infants from uncomplicated pregnancies. Inhibins and activin A levels were assayed by specific enzyme-linked immuno-sorbent assays. The paired t-test and linear regression analysis were used to calculate statistical significance. Inhibin A levels did not differ between the artery and vein of the umbilical cord. In contrast ,arterial inhibin B levels were significantly (p < 0.001) lower ,and activin A concentrations significantly (p < 0.05) higher than the respective venous concentrations. A significant correlation between arterial and venous levels of inhibin A (r = 0.591; p < 0.05) ,inhibin B (r = 0.749; p < 0.0001) and activin A (r = 0.571; p < 0.05) was found. The present findings suggest that the human placenta is the main source of inhibin B ,and the fetus of activin A ,in the umbilical cord. In light of the possible roles played by inhibin and activin in erythroid differentiation ,protection of neurons against brain injury and modulation of adrenal and pancreatic hormone release ,the present data may be of help in evaluating their changes in the umbilical cord when gestational diseases occur.     

Alterations of follicular microcirculation and apex structure during ovulation in the rat

Objective

We utilized methods for intravital microscopy and microcirculation measurements to study changes during ovulation.

Study design

Immature gonadotrophin-primed rats were laparotomized and one ovary was examined for morphological alterations during a 3 h period (covering a period from 1 h before to 27 h after hCG) through water-immersion lenses (maximum magnification 812×). Microcirculatory blood flow was assessed by measurements of blood cell velocity and laser Doppler flowmetry.

Results

Follicular hyperaemia was observed 30 min after hCG and then vasomotion was observed. A gradual decline of apical blood flow was seen, which later was associated with an avascular area over the top of the apex. Cells from the surface over the follicular apex were then detached from the exterior of the follicle and this phenomenon was initiated more than one hour prior to follicular rupture. The subsequent structural alterations varied with or without formation of a cone over the stigma. In ovulations with a stigma-cone, a translucent, irregular mass formed over the stigma. Prior to follicular rupture, granulosa cells and follicular fluid were extruded from the follicular cavity at a velocity of around 70 μm/s. Occasionally, intra-antral haemorrhage occurred prior to or during follicular rupture.

Conclusion

Characteristic features of ovulation in the rat are microcirculatory vasomotion, gradual formation of apical avascular area, specific changes of the stigma, and extrusion of the oocyte-granulosa cell complex with or without haemorrhage.     

Serum activin A and inhibin A elevated in pre-eclampsia: no relation to insulin sensitivity

OBJECTIVE: To assess the possible role of serum levels of activin A, inhibin A and pro-alpha inhibin (pro-alphaC) in insulin sensitivity in pre-eclampsia. DESIGN: A prospective study. SETTING: Helsinki University Central Hospital. PARTICIPANTS: Twenty-two nulliparous women with proteinuric pre-eclampsia and 16 healthy nulliparous controls in the third trimester of pregnancy. METHODS: Serum samples were collected before and after intravenous injection of glucose (0.3 g/kg) and insulin (0.03 IU/kg) (the minimal model for testing insulin sensitivity), and were assayed for activin A, inhibin A and pro-alphaC. MAIN OUTCOME MEASURES: Comparison of the levels of activin A, inhibin A and pro-alphaC between pre-eclamptic and healthy pregnant women, and the association of these proteins with insulin sensitivity. RESULTS: In pre-eclampsia elevated levels of activin A (139%, P = 0.0001), inhibin A (39%, P = 0.003), and pro-alphaC (92%, P = 0.0008) were observed. The amount of proteinuria (0.3-10.5 g/day) correlated positively with serum concentrations of activin A (P = 0.01) and inhibin A (P = 0.02). These glycoproteins were not associated with insulin sensitivity either in women with pre-eclampsia or controls. A 2.9-fold rise in blood glucose and a 52.5-fold rise in insulin during testing using the minimal model were not accompanied by any significant changes in activin A, inhibin A, and pro-alphaC. CONCLUSION: Activin A, inhibin A, and pro-alphaC are elevated in pre-eclampsia but do not appear to relate to the insulin sensitivity in pre-eclamptic or normal pregnancies.     

Inhibin A, inhibin B and activin A concentrations in umbilical cord artery and vein.

Activin A and inhibins (A and B) are growth factors expressed during pregnancy by the human placenta, decidua and fetal membranes, and by several fetal organs. They are secreted in both the maternal and the fetal circulations, but the net contribution of the fetus to inhibins/activin A production is still unclear. In the present study we determined whether there was a difference in the serum concentration of activin A, inhibin A and inhibin B between the artery and vein of the umbilical cord. Arterial and venous umbilical cord blood was obtained immediately before elective Cesarean section of 16 term infants from uncomplicated pregnancies. Inhibins and activin A levels were assayed by specific enzyme-linked immunosorbent assays. The paired t-test and linear regression analysis were used to calculate statistical significance. Inhibin A levels did not differ between the artery and vein of the umbilical cord. In contrast, arterial inhibin B levels were significantly (p < 0.001) lower, and activin A concentrations significantly (p < 0.05) higher than the respective venous concentrations. A significant correlation between arterial and venous levels of inhibin A (r = 0.591; p < 0.05), inhibin B (r = 0.749; p < 0.0001) and activin A (r = 0.571; p < 0.05) was found. The present findings suggest that the human placenta is the main source of inhibin B, and the fetus of activin A, in the umbilical cord. In light of the possible roles played by inhibin and activin in erythroid differentiation, protection of neurons against brain injury and modulation of adrenal and pancreatic hormone release, the present data may be of help in evaluating their changes in the umbilical cord when gestational diseases occur.     

Elevation of follicular phase inhibin and luteinizing hormone levels in mothers of dizygotic twins suggests nonovarian control of human multiple ovulation

OBJECTIVE: To determine whether multiple ovulation in mothers of spontaneous dizygotic (DZ) twins is because of higher hypothalamic stimulation or is in response to lower serum levels of ovarian inhibin. DESIGN: Serum hormone levels were measured at five times throughout the cycle in a sample of eight mothers of DZ twins and paired controls. On day 12, ovarian ultrasonography was performed. SETTING: Blood samples were collected in participants' homes except on day 12 when they were collected at the ultrasonography clinic. PATIENTS, PARTICIPANTS: Human volunteers who had at least one set of spontaneous DZ twins were paired with controls matched for age and parity. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Serum inhibin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) levels on approximate cycle days 1,2,8,12, and 21. RESULTS: Serum inhibin levels were elevated throughout the cycle (significantly on day 1) in mothers of DZ twins. Also elevated were early follicular FSH levels, LH levels throughout the follicular phase (significantly on days 1,2, and 8), and early to midfollicular E2 (significantly on day 8) in DZ mothers, indicative overall of greater follicular activity. CONCLUSION: It is concluded (1) that the primary cause of multiple ovulation in humans is not a decrease in inhibin secretion from the ovary; (2) the increased secretion of FSH and LH may be caused by elevated secretion of, or sensitivity to gonadotropin-releasing hormone; and (3) the elevated inhibin and E2 levels are a response to increased gonadotropin release.