Concentrations Of Ir-inhibin Research Articles

Changes in plasma concentrations of immunoreactive inhibin, progesterone, and bioactive gonadotrophin during pregnancy in the marmoset monkey.

This study describes the peripheral concentrations of immunoreactive (ir) inhibin, progesterone, and bioactive gonadotrophin during pregnancy in the marmoset monkey, a New World primate. Blood samples were taken every two weeks from six animals from ovulation to parturition. Plasma ir-inhibin concentrations were measured by inhibin α-subunit-directed radioimmunoassay (RIA) and a recently developed two-site immunoradiometric assay (IRMA) which is specific for inhibin αβ dimer. Concentrations of α-inhibin increased (P < 0.001) during early pregnancy to reach a peak on week 12 of pregnancy and showed a positive correlation with bioassayable gonadotrophin concentrations (r = 0.5, n = 64; P < 0.001). The concentrations of both α-inhibin and gonadotrophin showed no further peaks and declined (P < 0.001) to low levels prior to birth. Concentrations of dimeric inhibin were substantially lower than those measured by RIA and did not vary significantly during pregnancy. Progesterone concentrations remained at luteal-phase levels during the first half of pregnancy and increased (P < 0.05) during the second half to reach maximum concentrations just prior to birth. The relationship between α-inhibin, gonadotrophin, and progesterone suggests that the increase in α-inhibin may be luteal in source and under the control of gonadotrophin. The absence of a second increase in α-inhibin later in pregnancy and the finding that lategestation placenta contained very little α-inhibin differs from observations in Old World primates studied and suggests that the placenta may not be a source of inhibin during pregnancy in the marmoset. The finding of high levels of α-inhibin, but not dimeric inhibin, suggests that inhibin-related molecules may have a role other than suppression of pituitary folliclestimulating hormone. © 1994 Wiley-Liss, Inc.

Circulating concentrations of immunoreactive inhibin and FSH during the estrous cycle of mares

Summary A heterologous radioimmunoassay developed to measure inhibin in rat plasma was validated and used to characterize changes in peripheral concentrations of immunoreactive inhibin (ir-inhibin) in relation to follicle stimulating hormone (FSH) concentrations during the estrous cycle of mares. The primary antiserum used in the assay was developed against a synthetic porcine inhibin α-subunit [(1-26)-Gly-Tyr] fragment. The same synthetic peptide was used for preparation of standards and tracer. Slopes of the dose-response curves for pooled estrus and diestrus mare plasma and equine follicular fluid were similar to the slopes for the porcine inhibin α-subunit standard curve and porcine follicular fluid dose-response curve. Twelve mares were bled once daily beginning when diameter of the largest follicle reached ≤25 mm and continuing until 3 days after the end of an interovulatory interval (ovulation=Day 0). Each of the 12 interovulatory intervals were normalized to the mean length of the interovulatory interval (22.2 days; range, 19 to 26). There was an effect of day for concentrations of ir-inhibin (P

Increased concentrations of immunoreactive inhibin during conception cycles in the marmoset monkey: suppression with an LHRH antagonist and cloprostenol

Peripheral concentrations of immunoreactive (ir) inhibin have been measured during the ovarian cycle and early pregnancy in the marmoset monkey. Blood samples were taken (three per week) during conception (n = 6) and non-conception (n = 5) cycles. Ir-inhibin was measured by radioimmunoassay using an antiserum raised against a synthetic peptide fragment of the alpha subunit of human inhibin. Monomeric bovine alpha subunit and 32 kDa bovine inhibin were used as tracer and standard respectively. In all animals low concentrations of ir-inhibin were recorded during the follicular phase (40-60 micrograms/l) of the cycle. After ovulation, ir-inhibin concentrations increased but the peak concentrations attained differed between conception and non-conception cycles. In non-pregnant animals ir-inhibin concentrations reached a maximum of 242 +/- 16 micrograms/l on days 12/13 after ovulation. In pregnant animals ir-inhibin concentrations were significantly (P less than 0.05) higher (1.8-fold) than in non-pregnant animals on days 8/9 after ovulation, and reached a maximum value of 636 +/- 141 micrograms/l on days 20/21 after ovulation. Administration of an LHRH antagonist during the luteal phase on days 6-8 after ovulation resulted in a significant (P less than 0.05) decrease in progesterone and ir-inhibin concentrations within 4 and 8 h respectively. This was prevented by co-administration with human chorionic gonadotrophin. Administration of cloprostenol to pregnant animals between days 17 and 20 after ovulation halved the initial concentrations of both inhibin and progesterone within 1.5 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Peripheral concentrations of immunoreactive inhibin during pregnancy and parturition in the ewe

The aim of this study was to measure the peripheral concentrations of immunoreactive inhibin (ir-inhibin) and progesterone (P) during pregnancy and parturition in the ewe and to relate the concentrations of ir-inhibin to P and to the number and sex of the fetuses. P increased across pregnancy with higher levels in ewes with 2 fetuses (n = 5) than in those with 1 fetus (n = 6), and concentrations falling before birth. ir-Inhibin concentrations were relatively stable during the first 40 days of pregnancy for example (Day 20, 34.7 +/- 2.9 pmol L-1; mean +/- s.e.m., n = 11). After Day 40, inhibin fell in all ewes to reach less than or equal to 2.5 pmol L-1 after Day 80 (mean on Day 103, 6.3 +/- 1.2 pmol L-1), and remained low until 2 days before parturition when concentrations rose sharply, peaking at or around the day of birth in all ewes (21.5 +/- 2.1 pmol L-1). Thereafter, ir-inhibin fell and remained low or undetectable for up to 10 days in the six ewes still being sampled. ir-Inhibin concentrations in ewes carrying one (n = 6), two (n = 5) or three fetuses (n = 1) did not differ at any stage of pregnancy examined. The sex of the fetus did not appear to influence the peripheral concentrations of ir-inhibin in the ewe.

Circulating levels of inhibin in pregnant women at term: simultaneous disappearance with oestradiol and progesterone after delivery

Circulating levels of immunoreactive inhibin (ir-inhibin) and its disappearance after delivery of the placenta were determined in seven pregnant women at term. Serum oestradiol (E2) and progesterone (P4) levels were measured simultaneously and served as comparisons. Fetal contributions of ir-inhibin were assessed by determining concentrations in the umbilical artery (UA) and vein (UV). Relative changes in circulating levels of ir-inhibin, E2, and P4 were compared to levels found in nonpregnant women during the early follicular phase (EFP) and mid-luteal phase (MLP) of the normal menstrual cycle. In pregnant women, ir-inhibin levels at delivery were 15- and 3-fold higher than EFP and MLP values respectively. The disappearance of all three hormones after removal of the placenta followed a bi-exponential curve with an initial, rapid component and a second, slower component. There was a highly significant positive correlation between the disappearance curves of all three placental hormones (r = 0.97, P less than 0.0001). Concentrations of ir-inhibin in the cord blood were about half that in maternal serum and without significant difference between levels in UA and UV.

Concentrations of immunoactive inhibin in serum during human pregnancy: evidence for an ovarian contribution

Immunoactive inhibin (ir-inhibin) concentrations in maternal serum during normal human pregnancy have been established in two separate studies employing cross-sectional and longitudinal sampling regimes. Ir-inhibin concentrations rose from the mid-luteal phase (geometric mean + 95% confidence intervals 1.490 (1.086-2.028) U mL-1) to peak at week 11 of gestation (3.77 (3.26-4.35) U mL-1), declined to a plateau from 14 to 25 weeks with means ranging from 1.8 to 2.3 U mL-1, and subsequently rose slowly to a peak of 6.53 U mL-1 at 41 weeks. In the longitudinal study, similar results were obtained and no differences were found in maternal inhibin levels in women carrying male or female fetuses. Paired cord blood and maternal samples showed no significant difference in ir-inhibin concentrations irrespective of the sex of the fetus. However, in all such pregnancies amniotic fluid ir-inhibin levels were 2-3 fold greater than maternal or fetal levels raising the possibility that the amnion may secrete inhibin. In 12 women without functional ovaries in whom a singleton pregnancy was achieved by donation of oocytes and in vitro fertilization, the ir-inhibin levels showed a similar pattern in the first trimester of pregnancy but the concentrations achieved were markedly lower (peak 1.1 U mL-1 at 9 weeks). In five women from the group in whom samples were available late in gestation, three showed greater than normal levels and two had subnormal levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Accelerated dissolution of luteal-endometrial integrity by the administration of antagonists of gonadotropin-releasing hormone and progesterone to late-luteal phase women

Sequential blockade of gonadotropin-releasing hormone (GnRH) and progesterone (P) receptors by potent antagonists (Nal-Glu GnRH antagonist and RU486) was conducted in late-luteal phase women to develop a once-a-month birth control method by timed advancement of ongoing luteolysis and endometriolysis. Hormonal dynamics and timing of uterine bleeding during the antagonists' imposed luteal-follicular transition were compared with spontaneous (1st to 2nd) and recovery (2nd to 3rd) cycles in 10 normally cycling women. Serum luteinizing hormone (LH) and follicle-stimulating hormone levels declined (47 +/- 4.3% and 24 +/- 3.0%, respectively) by 24 hours after Nal-Glu injection, which accelerated the ongoing luteolytic process, as evidenced by more rapid declines of serum concentrations of estradiol, P, and ir-inhibin, as compared with the corresponding control cycle. This was accompanied by the prompt (16 +/- 3.2 hours after RU486) onset of a single episode of uterine bleeding, which was advanced by 2 days. Whereas the luteal phase length was foreshortened by 2 days, the subsequent follicular phase duration was prolonged by 2 days with a normal sequence of follicular maturation, LH surge, and luteal function during the recovery cycle. We conclude that the late-luteal sequential administration of antagonists of GnRH and P resulted in acceleration of the ongoing luteolytic and endometriolytic processes without functional alterations of the subsequent cycle.