Demonstration of a suppressive effect of inhibin alpha-subunit on the developmental competence of in vitro matured bovine oocytes

Changes in intrafollicular concentrations of different forms of inhibin (free alpha-subunits and alpha beta dimers) occur during follicle development and may influence the oocyte maturation process. The aim of this study was to investigate the effects of inhibin A and free alpha-subunit (pro-alpha C) isolated from bovine follicular fluid on maturation of bovine cumulus-oocyte complexes, as reflected by their competence for embryo development after in vitro fertilization. Bovine cumulus-oocyte complexes were isolated from ovaries obtained from an abattoir and were cultured for 22-24 h at 38.5 degrees C in TCM-199 medium supplemented with 10% oestrous cow serum, pregnant mares' serum gonadotrophin (2.5 iu ml-1) and either inhibin A (0, 0.2 and 1.0 microgram ml-1) or pro-alpha C (0, 2 and 10 micrograms ml-1). Neither inhibin A nor free alpha-subunit affected the cleavage rate of cumulus-oocyte complexes after fertilization (approximately 60%). Inhibin A reduced the proportion of cleaved oocytes reaching the eight-cell stage by 19% (P < 0.05), but did not affect the yield of blastocysts. However, pro-alpha C decreased the proportion of cleaved oocytes that reached the eight-cell (25%; P < 0.05) and blastocyst (28%; P < 0.05) stages. In addition, a negative correlation (r = -0.55, P < 0.001) was found between concentrations of total immunoreactive (ir) alpha-inhibin (measured by radioimmunoassay) produced by untreated control cumulus-oocyte complexes and their post-cleavage development to the blastocyst stage. In a second experiment, mouse monoclonal antibodies (20 micrograms ml-1) against two different regions of the inhibin alpha-subunit precursor (pro-region and alpha C fragment) were tested for their ability to neutralize endogenous inhibin alpha-subunit-related molecules produced by cumulus cells; control cumulus-oocyte complexes were treated with normal mouse IgG (20 micrograms ml-1). Although the cleavage rate was not affected, the yield of blastocysts was significantly higher in the presence of mouse monoclonal antibodies to both pro-alpha (77% increase; P < 0.05) and alpha C (48% increase; P < 0.05). None of the treatments tested affected endogenous production of activin-A or follistatin by cumulus-oocyte complexes. Overall, these results indicate that the inhibin alpha-subunit (pro-alpha C) has an inhibitory role in oocyte maturation which is independent of the modulatory effects of activin and follistatin.

A comparison of A103 and inhibin reactivity in adrenal cortical tumors: distinction from hepatocellular carcinoma and renal tumors

Distinguishing adrenal cortical neoplasms from either hepatocellular carcinomas or renal tumors can be difficult. Two recently described antibodies, A103 and inhibin A, are most often reported to be reactive with adrenal cortical neoplasms but with neither hepatocellular carcinoma nor renal cell carcinoma. To compare the sensitivity and specificity of these two antibodies in the diagnosis of adrenal cortical tumors, we stained 22 adrenal cortical adenomas, 4 adrenal cortical carcinomas, 25 hepatocellular carcinomas, and 43 renal tumors, including 33 renal cell carcinomas and 8 oncocytomas, with the A103 and inhibin A using an avidin-biotin complex technique. Fifteen (68%) of 22 adrenal adenomas and 2 (50%) of 4 adrenal cortical carcinomas were reactive with A103. Nineteen (86%) of 22 adrenal adenomas and 3 (75%) of 4 adrenal cortical carcinomas were reactive for inhibin A. None of the renal tumors or hepatocellular carcinomas reacted with A103, but 1 (4%) of 25 hepatocellular carcinomas (a high-grade pleomorphic tumor) and 1 (2%) of 43 renal tumors (a clear-cell renal cell carcinoma) were reactive with inhibin A. The cytoplasmic reactivity for A103 in adrenal tumors was coarsely granular and most common in clear-cell areas. Reactivity for inhibin was either cytoplasmic or membranous and stained both clear-cell and granular areas. We conclude that both antibodies are useful in the immunohistochemical diagnosis of adrenal cortical neoplasms and that A103 is slightly more specific and inhibin slightly more sensitive.

Activin antiserum infused into the lateral hypothalamic area affects operant behavior of rats fed lysine-deficient diet

Rats were trained to maintain a high rate of bar pressing to receive 50-mg pellets of a complete diet when given a lysine-deficient (Lys-def) diet ad libitum. This bar-pressing behavior was significantly inhibited when rats were also allowed ad libitum access to 0.4 M Lys to drink. A brain activin system may modulate motivation to engage in bar-pressing behavior, since previous work has established that antagonism of activin by infusion of inhibin or follistatin, but not activin, into the lateral hypothalamic area (LHA) also inhibits bar-pressing behavior. The present study sought to clarify whether the effect of inhibin or follistatin might be mediated by antagonism of endogenous activin or by a separate direct effect of inhibin or follistatin. Thus, we infused an antiserum, which specifically inhibits activin A activity, into the LHA. Infusion of antiserum greatly inhibited bar-pressing behavior of rats fed a Lys-def diet and was additive with Lys consumption further to decrease bar pressing. Ad libitum Lys consumption was unchanged from control levels, indicating that it is likely that an endogenous activin system in the LHA mediates behavioral responsiveness when rats are fed a Lys-def diet but does not appear specifically to affect appetite for Lys.

Display of an inhibin epitope in a surface-exposed loop of the E. coli heat-labile enterotoxin B subunit

In vitro gene manipulation was used to develop a novel chimeric antigen consisting of the non-toxic B subunit (EtxB) of an E. coli enterotoxin and the first 14 N-terminal amino acid residues of the carboxy-terminal portion of the alpha subunit of bovine inhibin (bINH1-14). Rabbits immunized subcutaneously (s.c.) or intravenously (i.v.) with EtxB::bINH1-14, with or without Freund's adjuvant, developed significant titres of antibodies that recognized an inhibin peptide fragment containing bINH1-14, native inhibins, and EtxB during separate enzyme-linked immunosorbent assay (ELISA). Passive immunization of mice with the rabbit anti-EtxB::bINH1-14 serum increased concentrations of follicle-stimulating hormone (FSH) in serum twofold compared with controls, whereas serum concentrations of luteinizing hormone (LH) were unaltered. Since FSH is the primary hormone from the pituitary gland that stimulates ovarian follicle growth and spermatogenesis, the results of this study demonstrate that EtxB::bINH1-14 has potential as antigen for development of inhibin-based fertility vaccines.

Immunocytochemical staining of ovarian cyst aspirates with monoclonal antibody against inhibin

Inhibin is a peptide hormone which is produced by ovarian granulosa cells during normal follicular development. It is important that granulosa cells are recognized in fine needle aspirates (FNAs) of ovarian cystic lesions, as this allows definite recognition of a functional cyst and exclusion of a potentially neoplastic epithelial lined cyst. Occasionally the distinction between granulosa and epithelial cells may be difficult, especially when aspirates from functional cysts are unusually cellular. In the present study, FNAs from 33 ovarian cystic lesions were immunostained with a monoclonal antibody against inhibin. Nine cases of peritoneal fluid containing malignant cells in patients subsequently confirmed to have ovarian adenocarcinoma were also stained. Where possible the cytological and immunocytochemical findings were correlated with subsequent biopsy. In most cases in which cytology suggested a functional cyst there was a strong positive staining with anti-inhibin, although occasional cases were negative. One case originally thought to contain epithelial cells stained strongly positive with anti-inhibin and on review was felt to represent a cellular functional cyst. In all other cases where cells were considered to be epithelial there was no staining with anti-inhibin. The study shows that immunocytochemical staining with anti-inhibin may be of value in confirming the presence of granulosa cells, thus establishing a diagnosis of functional cyst. Although negative staining does not exclude a functional cyst, positive staining with anti-inhibin allows exclusion of an epithelial lined cyst and may avoid unnecessary surgical intervention.

Effect of passive immunization against inhibin on FSH secretion, folliculogenesis and ovulation rate during the follicular phase of the estrous cycle in mares

Physiological roles of inhibin in mares were investigated by means of passive immunization using an antiserum to inhibin that had been raised in a castrated goat. Eight mares were given an intravenous injection of either 100 mL (n = 4) or 200 mL (n = 4) of inhibin antiserum 4 d after a single intramuscular injection of PGF2 alpha on Day 8 after ovulation, 4 control mares were treated with 100 mL castrated goat serum in the same manner. Jugular vein blood samples were collected after treatment with the serum until 192 h post treatment. Follicular growth and ovulations were monitored by ultrasound examination at 24-h intervals. The ability of the inhibin antiserum to neutralize the bioactivity of equine inhibin was examined in vitro using a rat pituitary cell culture system. Suppression of secretion of FSH from cultured rat pituitary cells by equine follicular fluid was reversed by the addition of increasing doses of the inhibin antiserum, thereby indicating its bioactivity. Plasma levels of FSH and estradiol-17 beta were higher in mares treated with the inhibin antiserum. The ovulation rate was significantly higher in mares treated with antiserum (100 mL = 3.75 +/- 0.63; 200 mL = 4.50 +/- 0.65) than in control mares (1.25 +/- 0.25). These results demonstrate that inhibin is important in regulating FSH secretion and folliculogenesis in mares. They also show that neutralization of the bioactivity of inhibin may become a new method for the control of folliculogenesis and ovulation rate in mares.

Effect of immunization against the amino-terminal peptide (alpha N) of the alpha 43-subunit of inhibin on follicular atresia and expression of tissue inhibitor of matrix metalloproteinase (TIMP-1) in ovarian follicles of sheep

Ewes actively immunized against alpha N, the N-terminal peptide of inhibin alpha 43 precursor, have lowered fertility associated with ovulation failure, restricted tissue remodelling and reduced matrix metalloproteinase-2 activity in the follicular fluid at the time of expected ovulation. This could be due to altered ratios of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase (TIMP-1), or to the onset of atresia in antral follicles destined to ovulate. The objectives of the present study were to investigate the effects of immunization against alpha N on the localization of TIMP-1 in ovine follicles, and on follicular growth and atresia in the follicular phase. Ewes were either immunized against alpha N or remained as controls and the ovaries were removed before (0, n = 4) and at 12 h (n = 4) and 24 h (n = 4) after hCG administration in a synchronized follicular phase, 48 h after removal of intravaginal pessaries. Observations were made on a single section taken through the largest follicle present in the ovaries of each ewe. There were no healthy antral follicles > 1 mm in immunized ovaries (0/29) compared with controls (16/31) (P < 0.001), whereas the proportion of healthy antral follicles < 1 mm was the same in each group (9/19 versus 5/12). TIMP-1 immunoactivity was localized in large luteal cells, smooth muscle and endothelial cells, and in all antral follicles, including oocytes. At the time of hCG administration, no TIMP-1 immunoreactivity was detected in the apical region of the follicular wall of large follicles (> 6 mm) compared with the rest of the follicle wall, but staining appeared in the apical granulosa layer 24 h later. In newly formed corpora lutea, TIMP-1 expression was found along the invaginating vascular layer. There was no effect of immunization on the patterns of TIMP-1 immunoreactivity, suggesting that changes in TIMP-1 are not involved in the effects of alpha N. These data are consistent with a paracrine role for alpha N in the selection and atresia of antral follicles, and for TIMP-1 in tissue reorganization and steroidogenesis at the time of ovulation.

Active immunization of Japanese quail hens with a recombinant chicken inhibin fusion protein enhances production performance

The effects of active immunization against inhibin on production performance in female Japanese quail (Coturnix coturnix japonica) were assessed in two separate trials using an MBP-cINA521 fusion protein as an immunogen. The fusion protein, MBP-cINA521, consisted of the bacterial maltose binding protein (MBP) and a truncated form of the mature alpha-subunit of chicken inhibin (cINA521). MBP-cINA1521 was constructed by: 1) excising a 521-bp PstI fragment from a chicken inhibin alpha-subunit cDNA (cINA6; gift of P. A. Johnson), 2) cloning this fragment, which encodes all but the first 11 amino acid residues of the mature alpha-subunit, into the pMal-c2 vector of the MBP fusion expression system, and 3) expressing the fusion protein (MBP-cINA521) from the Escherichia coli and purifying it using affinity chromatography. In each trial, quail were randomly and equally assigned to one of two injection treatments as follows: 1) MBP-cINA521 in Freund's adjuvant, or 2) Freund's adjuvant (vehicular controls; CON). All immunizations were given subcutaneously and Freund's complete and incomplete adjuvant were used for primary and booster injections, respectively. In Trial 1, birds were given a primary challenge of 0.2 mg MBP-cINA521 per bird at 25 d of age, followed by booster immunizations (0.1 mg MBP-cINA521 per bird) at 33, 40, 47, 54 and 61 d of age and every 35 d thereafter. The CON birds received vehicular immunizations at the same time intervals. In Trial 2, birds treated with MBP-cINA521 received a primary challenge of 0.2 mg MBP-cINA521 per bird at 26 d of age, followed by booster immunizations (0.1 mg MBP-cINA521 per bird) using the same schedule as that used in Trial 1, with the exception that no boosters were given after 61 d of age. The CON birds received vehicular immunizations at the same time intervals. Collection of production performance data was initiated coincident with the laying of the first egg in each trial (i.e., beginning at 41 and 44 d of age for Trials 1 and 2, respectively) and continued for 30 1-wk periods of lay. Combined data from Trials 1 and 2 indicated that the mean +/- SE age at first egg lay was markedly decreased (P < 0.005) in MBP-cINA521-treated quail (53.4 +/- 0.9 d of age) when compared to the CON (57.6 +/- 1.3 d of age). Likewise, the mean +/- SE age at 50% egg production was reduced (P < 0.03) in quail immunized against inhibin (65.4 +/- 2.1 d of age) when compared to the CON (77.6 +/- 4.7 d of age). Total hen-day egg production was also higher (P < 0.05, Trial 1; P < 0.01, Trial 2) in MBP-cINA521-treated quail (88.7 +/- 1.4%, Trial 1; 90.1 +/- 1.2%, Trial 2) than in the CON birds (81.9 +/- 2.9%, Trial 1; 73.6 +/- 6.5%, Trial 2). Collectively, these findings provide evidence that inhibin immunoneutralization accelerated puberty and enhanced hen-day egg production during a 30-wk period of egg lay in Japanese quail.

Total immunoreactive alpha-inhibin in human seminal plasma, sperm quality, and in vitro fertilization rates

OBJECTIVE

To assess the relationship between the concentrations of total immunoreactive alpha-inhibin in human seminal plasma, sperm quality, and in vitro fertilization (IVF) rates.

SETTING

Medical school hospital.

DESIGN

Prospective study.

PATIENTS

72 consecutive couples undergoing IVF with husband's sperm in which at least 4 oocytes were obtained.

MAIN OUTCOME MEASURES

Alpha-inhibin determination by means of enzyme-linked immunosorbent assay, sperm analysis for density and motility, IVF rates.

RESULTS

Total immunoreactive alpha-inhibin levels were not correlated with IVF rates. Nor were there any differences in fertilization rates in the different groups. Lower inhibin levels were found in oligozoospermic cases. Lower sperm counts were found in cases with inhibin values below the median value, and also with respect to various other cutoffs. No correlation was found between inhibin levels and any of the sperm variables measured.

CONCLUSION

Total immunoreactive alpha-inhibin is not a prognostic factor in IVF cycles. However, an association was found between inhibin and sperm concentration, suggesting that alpha-inhibin in the human seminal fluid could be a marker for some aspects of spermatogenesis.

Immunohistochemical study of testicular sex cord-stromal tumors, including staining with anti-inhibin antibody

Inhibin is a peptide hormone produced by ovarian granulosa cells and testicular Sertoli cells. Ovarian granulosa cell and other sex cord-stromal tumors usually exhibit positive immunohistochemical staining with antiinhibin antibodies, and this may be valuable in differentiating these neoplasms from histologic mimics. In the present study, we investigated the immunohistochemical staining of testicular sex cord-stromal tumors using antiinhibin. Immunostaining with CAM5.2, vimentin, S-100 protein, desmin, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), and placental alkaline phosphatase (PLAP) also was performed because few studies have investigated in detail the immunophenotype of testicular sex cord-stromal tumors. Fifteen of 16 Leydig cell tumors exhibited strong positive staining with antiinhibin. A proportion of Leydig cell tumors also stained positively with CAM5.2 (7 of 16), vimentin (14 of 16), S-100 protein (10 of 16), desmin (2 of 16) and epithelial membrane antigen (4 of 16). Four of six testicular sex cord-stromal tumors with varying degrees of Sertoli or granulosa cell differentiation were positive with antiinhibin, as were two of three sex cord-stromal tumors that were unclassified. Some of these tumors were positive with CAM 5.2, vimentin, S-100 protein, desmin, and epithelial membrane antigen. All tumors were negative with carcinoembryonic antigen and placental alkaline phosphatase. The immunohistochemical findings show that, analogous to their ovarian counterparts, most testicular sex cord-stromal tumors are immunoreactive with antiinhibin. Immunohistochemistry using this antibody as part of a panel may be valuable in confirming a diagnosis of testicular sex cord-stromal tumor and in differentiating these neoplasms from others that may mimic them.

Suppression of IL-6 biological activities by activin A and implications for inflammatory arthropathies

Activin A is a cytokine whose multiple functions have yet to be fully determined. In this study, the role of proinflammatory cytokines in regulatory control of activin A production was shown in synoviocytes and chondrocytes. Additional facets of functional inflammation-related activities of activin A were also determined. Results showed that activin A concentrations in the synovial fluid of patients with rheumatoid arthritis and gout were elevated relative to those in patients with osteoarthritis. Further studies showed that production of activin A by synoviocytes and chondrocytes in culture was stimulated by cytokines such as IL-1, transforming growth factor-beta (TGF-beta), interferon-gamma (IFN-gamma), and IL-8, consistent with previous studies in regard to the control of activin A production in marrow stromal cells and monocytes by cytokines, glucocorticoids and retinoic acid. In addition, the relationship of activin A to IL-6-induced biological activities was investigated. Three major IL-6 activities involved in inflammatory responses were found to be suppressed by activin A. In a dose-dependent manner, activin A efficiently suppressed IL-6-induced proliferation of 7TD1 B lymphoid cells, phagocytic activity of monocytic M1 cells, and fibrinogen production in HepG2. Therefore, it is likely that activin A serves as a suppressor for IL-6, dampening inflammatory responses, and has the potential to perform some previously unrecognized roles in inflammation.

Effects of passive immunization using antibody against an alpha-inhibin peptide on follicle-stimulating hormone concentrations and litter size in sows

The objective of the experiment was to determine whether passive immunization against inhibin at weaning would increase FSH secretion and thereby influence postweaning reproductive performance in sows. Commercial Yorkshire sows (n = 173) were assigned within parity to 5 alpha-inhibin fragment antibody (alpha-IF-Ab) dosage groups: 0 (control), 3.25, 6.5, 13 and 26 RP-2 kU/kg alpha-IF-Ab. Antibody had been semipurified from ovine antisera raised against alpha-IF, a peptide that mimicked the N-terminal region of inhibin's alpha-subunit. A RP-2 U refers to a laboratory reference preparation. Sows were administered a single intramuscular injection of control solution or alpha-IF-Ab just before 21-d-old piglets were weaned. Blood samples were taken immediately before immunization and 24 h later. Sows were bred upon expression of estrus. Serum alpha-IF-Ab titers in sows 24 h following passive immunization increased (P < 0.001) with dosage. In control sows serum FSH concentrations decreased 24% by 24 h postweaning (P < 0.001). The decrease was diminished or prevented by alpha-IF-Ab treatment in a dose-responsive manner (P < 0.001). Most (167/173) sows were bred within 10 d postweaning, and wean-to-service intervals tended (P < 0.1) to be shorter in the 13 and 26 RP-2 kU/kg alpha-IF-Ab dosage groups. Farrowing rate was 72% (124/173) and was similar among sows in the alpha-IF-Ab dosage groups. Litter size, expressed as total or live piglets born per sow or per sow farrowed, was unchanged by alpha-IF-Ab treatment. Results demonstrate that 1) inhibin plays a key role in regulating FSH secretion at weaning, and 2) blocking the acute postweaning drop in FSH secretion has little if any effect on subsequent reproductive performance.

Inhibin A concentrations in the sera of young women during and after chemotherapy for lymphoma: correlation with ovarian toxicity

PROBLEM

Inhibin A concentrations in serum may reflect the ovarian granulosa cell compartment. To characterize the correlation between ovarian function after gonadotoxic chemotherapy for Hodgkin's or non-Hodgkin's lymphoma in young women, the immunoreactive inhibin A concentrations in the sera of these patients was measured before, during, and after the gonadotoxic chemotherapy.

METHOD OF STUDY

A prospective clinical protocol was undertaken in 20 cycling women with lymphoma, aged 15-40 years. A monthly injection of depot D-TRP6-GnRH-a (Decapeptyl CR, Ferring) was administered from before starting the chemotherapy until its conclusion, up to a maximum of six monthly injections. Most of the patients were treated with the mustargen-oncovin-procarbazine-prednisone (MOPP)/actinomycin D-bleomycin-vincristine (ABV) chemotherapy combination; 13 with and 7 without radiotherapy. A hormonal profile [follicle-stimulating hormone (FSH), luteinizing hormone (LH), 17-beta-estradiol (E2), testosterone (T), progesterone (P4), insulin-like growth factor (IGF)-1, IGF-BP3, and prolactin (PRL)] was taken before starting the gonadotropin-releasing hormone agonist (GnRH-a)/chemotherapy co-treatment and monthly thereafter until resuming spontaneous ovulation and menstrual cyclicity. This group of prospectively treated lymphoma patients was compared with a control group of 22 regularly cycling women who had been treated with chemotherapy (mostly MOPP/ABV) with or without radiotherapy for Hodgkin's or non-Hodgkin's lymphoma. Inhibin A immunoactivity developed by Nigel Groome was measured by an enzyme-linked immunoadsorbent assay (ELISA) commercial kit (Serotec).

RESULTS

Whereas all but one (40 years of age) of the surviving patients in the GnRH-a/chemotherapy co-treatment group resumed spontaneous ovulation and menses within 6 months, only one half of the patients in the "control" group (chemotherapy without GnRH-a co-treatment) resumed ovarian function and regular cyclic activity (P < 0.05). The remaining 50% experienced premature ovarian failure (POF). Temporarily increased FSH concentrations were experienced by approximately one third of the patients resuming cyclic ovarian function, suggesting a reversible ovarian damage in a larger proportion of women than those experiencing POF. The inhibin A immunoactive concentrations decreased during the GnRH-a/chemotherapy co-treatment but increased to normal levels in patients who resumed regular ovarian cyclicity, and/or spontaneously conceived, as compared to low levels in menopausal women and those who had developed POF.

CONCLUSIONS

If these preliminary data are consistent in a larger group of patients, inhibin A concentration may serve as a prognostic factor for predicting the resumption of ovarian function, in addition to the levels of FSH, LH, and E2.

Effects of passive immunization against oestradiol-17beta and inhibin on the secretion of gonadotrophin in the cyclic golden hamster (Mesocricetus auratus)

To investigate the physiological importance of oestradiol-17beta and inhibin in the regulation of gonadotrophin secretion in the cyclic golden hamster, females were passively immunized against two hormones. When 200 microL antiserum against oestradiol-17beta (oestradiol-AS) was given on Day 3 (Day 1 = day of ovulation), the preovulatory gonadotrophin surge was completely blocked for 24 h and the length of the oestrous cycle was also prolonged for one day. In the group given 200 microL oestradiol-AS on Day 3, basal levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) increased slightly and superovulation (19.6+/-0.8, mean+/-s.e.m.) occurred. When 200 microL antiserum against inhibin (inhibin-AS) was given at 1100 hours on Day 3, a dramatic increase in plasma FSH and a slight increase in LH were noted, resulting in superovulation (38.2+/-2.6) on the expected Day 1. The present study indicates clearly that inhibin plays a major role in regulating the specific ovulation rate in the hamster through the control of FSH secretion. Present results also indicate that oestradiol-17beta suppresses basal LH secretion. Oestradiol-17beta may act as an indicator of the follicular maturation, and the high plasma concentration of oestradiol-17beta noted from Day 3 to Day 4 may play an important role in determining the timing of initiation of the preovulatory gonadotrophin surge.

Ovarian response and FSH profile in cows following injection of various doses of inhibin antiserum

Dose effect of inhibin antiserum on ovarian response and hormonal profiles were investigated. On day 12 of the estrous cycle (day 0 = estrus), 14 of 19 cows were given a single i.v. injection of 25 ml (n = 4), 37.5 ml (n = 5) or 50 ml (n = 5) antiserum against inhibin produced in a castrated male goat. The other 5 animals were given 50 ml castrated male goat serum (control serum). The animals in each group received a single i.m. injection of 0.5 mg prostaglandin F2 alpha analogue (PG) 48 hr following the serum injection. The population of follicles and ovulation rate (estimated by the number of corpora lutea) were examined by ultrasonography. Administration of inhibin antiserum consistently resulted in a significant (p < 0.01) increase in plasma concentrations of follicle-stimulating hormone (FSH) in inhibin-neutralized groups, although the increased FSH levels were sustained longer in 50-ml group than in the 25- and 37.5- ml groups. Levels in the circulating inhibin antibody titer were positively correlated with dosage of inhibin antiserum. A large number of antral follicles (> or = 4 mm in diameter) developed similarly after hypersecretion of FSH in all neutralized groups, coupled with a rise in plasma estradiol levels, while the number of large follicles (> or = 10 mm in diameter) on estrus showed a dose-dependent increase. Multiple ovulation (2 to 4) was recorded in all animals after injection of 50 ml inhibin antiserum, however all cows in the 25-ml group experienced only one ovulation and injection of 37.5 ml resulted in a variable number of ovulations (1 to 5). These results demonstrated that administration of inhibin antiserum on day 12, followed by injection of PG, was able to induce hypersecretion of FSH and subsequently multiple ovulations. The number of large follicles on estrus day and ovulations were affected by dosage of inhibin antiserum and were correlated with persistence of increased FSH levels or circulating antibody levels.

Inhibin immunohistochemistry applied to ovarian neoplasms: a novel, effective, diagnostic tool

Immunohistochemistry using monoclonal antibodies against human inhibin, a peptide hormone produced by ovarian granulosa cells to inhibit follicle-stimulating hormone (FSH), has been recently applied to diagnostic anatomic pathology. This investigation hypothesizes that inhibin immunohistochemistry will aid in the crucial clinical distinction between sex cord-stromal and other primary ovarian neoplasms. Available H&E slides and clinical information from a retrospective surgical series of 186 primary ovarian tumors were reviewed to verify diagnoses, and representative paraffin sections were immunostained with anti-inhibin (R1 monoclonal, Serotec, Kidlington, Oxford, UK). Immunoreactivity was graded as weak/strong (W/S), and the proportion of strong staining cells was coded as follows: S1 = <10%, S2 = 10%-50%, S3 = >50%, respectively. Inhibin immunoreactivity for 137 sex cord-stromal lesions was as follows: 100% of 66 granulosa cell tumors: 80% S3, 20% S2; 100% of 17 Sertoli-stromal tumors: 90% S3, 10% S2; 100% of 13 hyperplastic follicular/stromal lesions: 90% S3, 10% S2; 100% of six steroid cell tumors: 100% S3; 90% of 18 thecomas: 40% S3, 10% S2, 10% S1, 30% W; 0% of 12 fibromas, three myxomas, and two sclerosing stromal tumors. None (0 of 49) of the other ovarian neoplasms exhibited inhibin: 22 carcinomas, 12 carcinosarcomas, seven small cell carcinomas, six germ cell tumors, and two lymphomas. In the typical case, the distinction between sex cord-stromal and other ovarian neoplasms requires nothing more than routine pathological examination. In diagnostically challenging cases, our data indicate that inhibin immunohistochemistry is a very useful adjunct because granulosa and sertoli-stromal tumors are positive whereas other potential mimickers have been negative thus far.

Follicle-stimulating hormone enhances the development of preantral follicles in juvenile rats

The stimulatory effects of gonadotropins on antral and preovulatory follicles are well known, but conflicting results have been reported regarding the gonadotropin responsiveness and dependency of preantral follicles. Taking advantage of the relatively uniform development of the first wave of follicles in the postnatal rat ovary, we evaluated the role of endogenous and exogenous gonadotropins on preantral follicle development. Reduction of the high levels of gonadotropins present in juvenile rats by either hypophysectomy (at Day 15) or GnRH antagonist treatment (starting from Day 11 of age) resulted in decreased ovarian weight at Day 19 of age that was associated with a reduced number of developing follicles and increased atresia of remaining follicles. In contrast, treatment with FSHctp (a long-acting FSH agonist) in intact (Days 5-19 of age), hypophysectomized (Days 15-19), or GnRH antagonist-treated (Days 11-19) animals resulted in increased ovarian weight and follicle development as determined histologically and by inhibin-alpha expression. A dose-dependent stimulatory effect of hCG on ovarian weight was seen when animals were cotreated with FSHctp and the GnRH antagonist. At low doses of hCG, augmentation of antral follicle formation occurred, whereas higher doses of hCG led to morphological signs of luteinization. These findings demonstrate the important role of endogenous gonadotropins in preantral follicle development and indicate that preantral follicles are highly responsive to exogenous gonadotropins.

Immunohistochemical staining of ovarian granulosa cell tumors with monoclonal antibody against inhibin

Inhibin is a peptide hormone produced by ovarian granulosa cells and by granulosa cell tumors. Serum inhibin measurements have been used as a biochemical marker of the presence or progression of ovarian granulosa cell tumors and their metastases. In the current study, an antibody against the alpha-subunit of human inhibin was used to stain 16 cases of ovarian adult granulosa cell tumors, 15 cases of other ovarian sex cord-stromal tumors, and 51 cases of a range of ovarian and extraovarian neoplasms, many of which may mimic granulosa cell tumor. There was diffuse strong cytoplasmic staining of all cases of adult granulosa cell tumor. Diffuse positive staining also was observed in all Leydig cell tumors, and there was focal staining in a proportion of fibrothecomas. There was focal weak staining of one case of ovarian clear cell carcinoma but no staining of other ovarian and extraovarian neoplasms. Immunohistochemical staining with antibodies against inhibin is of value in the diagnosis of granulosa cell tumor and in the distinction of this neoplasm from others that may mimic it. The antibody also may be useful for the confirmation of late metastasis of granulosa cell tumor, especially when the previous history is not known.

Effect of peptide to carrier ratio on the immune and ovarian response to inhibin immunization in cattle

We report on the effects of the peptide to carrier ratio on the immune and biological response to inhibin immunization in cattle. A peptide sequence from the alpha C-subunit of bovine inhibin was synthesized and conjugated to human serum albumin (HSA) at ratios of 4.3 moles (L) and 13.1 moles (M) of peptide per mole of HSA. Hereford-cross heifers (n = 6 per group) were injected with 3 mg of one of the peptide conjugates at primary, followed by a booster injection (1.5 mg) 11 weeks later. Control heifers (n = 6) were injected with HSA only. Blood samples were taken at regular intervals to measure antibody titre. Ovulation rate was measured by ultrasonography. Antibodies were generated in both peptide immunized groups. Control heifers and group L heifers had 1 ovulation at all ovulatory cycles monitored. Ovulation rate was increased (P < 0.05) in group M immunized heifers, with four of six heifers having twin ovulations in the first cycle following boost. These data support those of previous studies which indicated that immunization against the alpha C-subunit of bovine inhibin significantly disrupted the mechanism(s) controlling ovulation rate in cattle. It also indicates that both the immune and associated biological response is dependent on the nature of the conjugate used for immunization, specifically the ratio of peptide to carrier.

Inhibin is involved in the suppression of FSH secretion in the growth phase of the dominant follicle during the early luteal phase in cows

This study was carried out to examine the involvement of inhibin in the regulation of FSH secretion during the growth phase of the dominant follicle in the early luteal phase of cows. Six cows were given a single i.v. bolus injection of 100 ml inhibin antiserum raised against bovine 32-kDa inhibin in a castrated male goat, and five animals received the same amount of castrated male goat serum (control serum) on Day 5 of the estrous cycle (Day 0 = estrus). All animals in each group experienced a wave of follicular development after ovulation, and the dominant follicle was over 8.5 mm in diameter on Day 5. The corpus luteum was identified for each group on Day 5. Plasma concentrations of estradiol and progesterone gradually increased after ovulation and reached around 3.7 pg/ml and 3.0 ng/ml on Day 5, respectively, suggesting that the dominant follicle and corpus luteum were functional. Administration of inhibin antiserum produced a clear increase (P < 0.001) in plasma FSH within 8 hr compared with that in control animals. Plasma levels of luteizing hormone showed a moderate increase during 40 hr after the injection of antiserum (P = 0.08). A large number of antral follicles (4 mm in diameter) developed after the hypersecretion of FSH, coupled with the rise in plasma estradiol levels. These results clearly demonstrated that inhibin neutralization during the early luteal phase produces hypersecretion of FSH with a coincident stimulation of follicular development, indicating that inhibin is an important factor for the negative regulation of FSH secretion during the early luteal phase when secretion of estradiol and progesterone are normally high.

Effects of supplementary treatment with bovine growth hormone on hormonal and ovulatory responses to inhibin immunization in ewes

The aim of this study was to determine whether supplementary treatment with recombinant bovine growth hormone(rbGH) can enhance the ovulatory response of ewes to inhibin immunization. Crossbred ewes (n = 20) were actively immunized against bovine inhibin a1-29 peptide conjugate while 20 ewes served as controls. Oestrus was synchronized using progestagen sponges and ewes were allocated to four groups: control ewes (n = 10); control ewes given rbGH (n = 10); inhibin-immunized ewes (n = 10) and inhibin-immunized ewes given rbGH (n = 10). A single s.c. dose of rbGH (50 mg) was given 7 days before sponge removal. Blood was collected for measurement of inhibin antibody titre, and concentrations of insulin-like growth factor I (IGF-I), FSH, oestradiol and progesterone. Ovulation, pregnancy and lambing rates were also recorded. All inhibin-immunized ewes produced antibodies that bound 125I-labelled (32 kDa) inhibin. The concentration of FSH in the plasma of the ewes after the second booster inhibin immunization was higher than that in control ewes (P < 0.005). Treatment with rbGH promoted a 2-3-fold increase in plasma concentration of IGF-I (P < 0.001); the response was less (P < 0.01) in immunized compared with control ewes. Treatment with rbGH alone had no significant effect on the concentration of FSH or oestradiol or on ovulation rate or litter size. Overall, inhibin-immunized ewes had higher mean FSH concentrations (P < 0.002), higher preovulatory oestradiol surges (P < 0.05) and higher progesterone concentrations in the luteal phase (P < 0.0001). Treatment with rbGH reduced the effects of immunization on FSH (P < 0.01) and progesterone (P < 0.02) concentrations. Immunized ewes showed a threefold increase in ovulation rate (P < 0.001) and a 1.8-fold increase in litter size (P < 0.05) compared with control ewes. In immunized ewes given rbGH, ovulation rate was increased by a factor of 2.2 and litter size by a factor of 1.8. In conclusion, these data do not support the hypothesis that supplementary treatment of ewes with rbGH to raise plasma IGF-I concentrations (and presumably intraovarian IGF-I) can enhance the ovulatory response to inhibin immunization.

Immunohistochemical staining of hepatocellular carcinoma with monoclonal antibody against inhibin

Inhibin is a peptide hormone produced by ovarian granulosa cells. During a recent study investigating the immunohistochemical staining of ovarian granulosa cell tumours and other neoplasms with an anti-inhibin monoclonal antibody, we identified strong cytoplasmic staining of hepatocytes. In the present study we investigated the immunostaining of hepatocellular carcinoma and other neoplasms involving the liver with anti-inhibin to determine whether the antibody may be of value in the differential diagnosis of hepatic neoplasms. Immunostaining for alpha-fetoprotein was also performed. With anti-inhibin there was positive, generally strong, cytoplasmic staining of 17 of 19 cases of hepatocellular carcinoma, including the pleomorphic and glandular variants. There was positive staining of six of 20 cases of adenocarcinoma. In these, positive staining was generally focal, of weak intensity and involved the luminal surface of neoplastic glands. There was no staining of five cases of neuroendocrine tumour. There was positive staining for alpha-fetoprotein in 13 of 19 cases of hepatocellular carcinoma and in two of 20 cases of adenocarcinoma but no staining of neuroendocrine tumours. Immunostaining with anti-inhibin antibody may be of value in the differentiation of hepatocellular carcinoma from other neoplasms involving the liver. The antibody is a more sensitive, but less specific, immunohistochemical marker for hepatocellular carcinoma than is alpha-fetoprotein.

Contributions of endogenous inhibin and estradiol to the regulation of follicle-stimulating hormone and luteinizing hormone secretion in the pregnant rat

To examine the contributions of endogenous inhibin and estradiol to the regulation of FSH and LH secretion in the pregnant rat, some rats were passively immunized against inhibin and/or estradiol, and others were ovariectomized, on Days 5, 10, 15, and 20 of pregnancy. Ovarian and uterine venous blood was collected separately to confirm the sources of inhibin and steroid hormones during pregnancy. Immunoreactivity of inhibin in the placenta was also examined by RIA. Levels of inhibin in ovarian venous plasma were significantly higher than those in peripheral plasma during pregnancy. No difference was observed between the levels of inhibin in uterine venous plasma and peripheral plasma. No immunoreactivity of inhibin was detected in placental homogenate from rats at Days 10, 15, and 20. FSH secretion significantly increased after immunoneutralization of inhibin during pregnancy. A marked increase in FSH secretion was noted on Days 5 and 20, and the smallest increase was observed on Day 15. Administration of estradiol antiserum (AS) alone did not induce a significant increase in FSH secretion on any day of pregnancy. However, a synergistic effect of estradiol AS and inhibin AS was observed on Day 20. On Days 5, 10, and 20, administration of inhibin AS or estradiol AS induced a significant increase in LH secretion. A synergistic effect of inhibin AS and estradiol AS on LH secretion was observed on Day 5. On Days 5 and 10, significantly high LH secretion was noted in ovariectomized rats as compared with that in rats treated with both inhibin AS and estradiol AS, indicating that other ovarian hormones such as progesterone may be involved in the suppression of LH secretion in these stages of pregnancy. These data indicate that both inhibin and estradiol, predominantly secreted from the ovary, are involved in the regulation of gonadotropin secretion during pregnancy as during the estrous cycle in the rat.

Use of monoclonal antibody against human inhibin as a marker for sex cord-stromal tumors of the ovary

Inhibin is a glycoprotein hormone produced by normal ovarian granulosa cells and testicular sertoli cells. In the ovary, it inhibits the secretion of follicle-stimulating hormone. Patients with granulosa cell tumors (GCT) have elevated serum levels of inhibin and this finding has been used to detect recurrent tumor. This study attempts to determine whether inhibin antibody (IAB) can preferentially mark GCT and Sertoli-cell or Sertoli-Leydig cell tumors (SCT) in paraffin-embedded tissues and facilitate distinction of GCT from small cell carcinoma of hypercalcemic type (SCC), SCT from Sertoliform endometrioid carcinoma (SEC), and primitive gonadal-stromal tumors from a variety of poorly differentiated neoplasms. Applying microwave-enhanced immunohistochemistry, a total of 126 paraffin-embedded and microwave-enhanced archival ovarian tumors and tissues were studied by using monoclonal IAB. The tumors included 32 adult GCT, 7 juvenile GCT, 4 metastatic GCT, 8 SCT, 7 SCC, 6 primitive gonadal stromal tumors (PGST), 5 fibrothecomas, 6 lipid cell tumors (LCT), 5 extrauterine endometrial stromal sarcomas (ESS), 5 hemangiopericytomas (HPC), 1 metastatic malignant melanoma, 1 metastatic malignant lymphoma, and 27 epithelial tumors including 8 SEC, 5 mucinous tumors, and 4 Brenner tumors. Seven pregnancy luteomas (nodular theca lutein hyperplasia of pregnancy), 3 corpora lutea and 2 ovarian follicles were also studied. The intensity of immunostaining was scored from one to three and the percentage of the immunoreactive tumor cells was determined and expressed in 10% increments. Among 32 adult GCT, 31 (97%) tumors reacted positively with IAB. The percent of positive cells ranged from 30% to 100% (average 80%). Similarly, all four metastatic GCT, 7 juvenile GCT and 4 of 5 fibrothecomas were immunoreactive with monoclonal IAB. Seven of 8 (88%) SCT, 5 of 6 (83%) PGST, all 6 LCT, 7 pregnancy luteomas, 3 corpora lutea and the 2 ovarian follicles were also positive with IAB. The most intense positivity was observed in luteinized stromal cells regardless of tumor type. No immunoreactivity was observed in any of the 7 SCC, 5 ESS, 5 HPC, 1 metastatic malignant melanoma, 1 metastatic malignant lymphoma and the epithelial component of all 27 epithelial tumors including 8 SEC. Among the mucinous tumors of the ovary, however, 3 tumors with luteinized stromal cells showed immunoreactivity in these cells, but no positivity was seen in the mucinous epithelium. We conclude that IAB is an excellent marker for sex cord differentiation in ovarian tumors. It can be used effectively in the diagnosis of GCT and its distinction from epithelial neoplasms particularly SCC. The IAB may also be helpful in differentiating LCT from epithelial malignancies. However, it cannot be used to distinguish GCT from SCT.