In vivo and in vitro evidence for the production of inhibin-like immunoreactivity in human adrenocortical adenomas and normal adrenal glands: relatively high secretion from adenomas manifesting Cushing's syndrome

Inhibin-A and inhibin-B in cyclic and pregnant mares, and mares with granulosa-theca cell tumors: Physiological and diagnostic implications

Studies in mares have examined serum inhibin concentrations using immuno-assays unable to distinguish dimeric inhibin-A from inhibin-B isoforms. Inhibin-A and inhibin-B immuno-assays were used to investigate concentrations in cyclic mares, young and old (6 vs 19 years old, respectively) mares following hemi-ovariectomy, mares during pregnancy and in mares with confirmed granulosa cell tumors (GCTs). Mares with inter-ovulatory intervals of 26 days had ovulatory peaks of inhibin-A averaging 80 pg/mL with a mid-cycle nadir of 5 pg/mL. Inhibin-A and inhibin-B concentrations were highly correlated (r = + 0.79, P < 0.01) though peak and nadir concentrations of inhibin-B were not significantly different. However, the ratio of inhibin-A to inhibin-B (A/B) changed significantly through the cycle, highest at ovulation and <1 (more inhibin-B than -A) at mid-cycle. Two mares with grossly extended inter-ovulatory intervals demonstrated mid-cycle inhibin-A (and inhibin-B) excursions suggestive of follicular waves. Follicle-stimulating hormone was negatively correlated with inhibin-A and -B concentrations in all 6 mares. Hemi-ovariectomy in young mares resulted in a significant decrease in inhibin-A and inhibin-B concentrations one day later (P < 0.05) but older mares did not, suggesting a possible extra-ovarian source(s) of these hormones. Both inhibin isoforms dropped to very low levels during pregnancy (P < 0.0001), inhibin-A (P < 0.0001) more rapidly than -B (P < 0.05), so that inhibin-B became the predominant measured form throughout most of gestation (P < 0.05). Mares with confirmed GCTs had elevated inhibin-B concentrations more reliably than inhibin-A but neither inhibin-A or -B was correlated with anti-Müllerian hormone concentrations. Collectively, concentrations of inhibin-A and -B were aligned with physiological events in healthy mares, though more pronounced cyclic changes were seen with inhibin-A. Inhibin-B concentrations were significantly associated with GCTs (P < 0.01), inhibin-A concentrations were not. While both inhibin-A and -B concentrations track physiological events such as cyclic follicular activity, only inhibin-B concentrations effectively signal ovarian neoplasia in mares.

Inhibin alpha-subunit (INHA) expression in adrenocortical cancer is linked to genetic and epigenetic INHA promoter variation

Adrenocortical carcinoma (ACC) is a rare, but highly malignant tumor of unknown origin. Inhibin α-subunit (Inha) knockout mice develop ACCs following gonadectomy. In man, INHA expression varies widely within ACC tissues and its circulating peptide inhibin pro-αC has been described as a novel tumor marker for ACC. We investigated whether genetic and epigenetic changes of the INHA gene in human ACC cause loss or variation of INHA expression. To this end, analyses of INHA sequence, promoter methylation and mRNA expression were performed in human adrenocortical tissues. Serum inhibin pro-αC levels were also measured in ACC patients. INHA genetic analysis in 37 unique ACCs revealed 10 novel, heterozygous rare variants. Of the 3 coding bases affected, one variant was synonymous and two were missense variants: S72F and S184F. The minor allele of rs11893842 at -124 bp was observed at a low frequency (24%) in ACC samples and was associated with decreased INHA mRNA levels: 4.7±1.9 arbitrary units for AA, compared to 26±11 for AG/GG genotypes (P = 0.034). The methylation of four proximal INHA promoter CpGs was aberrantly increased in five ACCs (47.7±3.9%), compared to normal adrenals (18.4±0.6%, P = 0.0052), whereas the other 14 ACCs studied showed diminished promoter methylation (9.8±1.1%, P = 0.020). CpG methylation was inversely correlated to INHA mRNA levels in ACCs (r = -0.701, p = 0.0036), but not associated with serum inhibin pro-αC levels. In conclusion, aberrant methylation and common genetic variation in the INHA promoter occur in human ACCs and are associated with decreased INHA expression.

Autocrine/paracrine regulatory mechanisms in adrenocortical neoplasms responsible for primary adrenal hypercorticism

A wide variety of autocrine/paracrine bioactive signals are able to modulate corticosteroid secretion in the human adrenal gland. These regulatory factors, released in the vicinity of adrenocortical cells by diverse cell types comprising chromaffin cells, nerve terminals, cells of the immune system, endothelial cells, and adipocytes, include neuropeptides, biogenic amines, and cytokines. A growing body of evidence now suggests that paracrine mechanisms may also play an important role in the physiopathology of adrenocortical hyperplasias and tumors responsible for primary adrenal steroid excess. These intra-adrenal regulatory systems, although globally involving the same actors as those observed in the normal gland, display alterations at different levels, which reinforce the capacity of paracrine factors to stimulate the activity of adrenocortical cells. The main modifications in the adrenal local control systems reported by now include hyperplasia of cells producing the paracrine factors and abnormal expression of the latter and their receptors. Because steroid-secreting adrenal neoplasms are independent of the classical endocrine regulatory factors angiotensin II and ACTH, which are respectively suppressed by hyperaldosteronism and hypercortisolism, these lesions have long been considered as autonomous tissues. However, the presence of stimulatory substances within the neoplastic tissues suggests that steroid hypersecretion is driven by autocrine/paracrine loops that should be regarded as promising targets for pharmacological treatments of primary adrenal disorders. This new potential therapeutic approach may constitute an alternative to surgical removal of the lesions that is classically recommended in order to cure steroid excess.

Inhibins and activins: their roles in the adrenal gland and the development of adrenocortical tumors

The adrenal gland is composed of two separate endocrine tissues that control a multitude of bodily functions in their adaptation to external and internal stressors through hormone secretion. The functions of the adrenal gland are regulated by circulating, neural and local factors that ensure proper cell growth and hormone production. Activins and inhibins are among the locally expressed growth factors affecting adrenal cell function. They have been found to influence several aspects of adrenal cell development, adrenocortical steroidogenesis, adrenocortical tumor formation and adrenomedullary cell differentiation. Especially the finding that inhibin α-subunit knockout mice develop adrenocortical carcinomas after gonadectomy has prompted research on the physiological and pathophysiological roles of activin and inhibin in the adrenal cortex. It is now clear that both peptides control adrenocortical physiology and are involved in adrenocortical tumorigenesis at multiple levels, both in murine models as well as in human patients.

Serum inhibin pro-αC is a tumor marker for adrenocortical carcinomas

OBJECTIVE

The insufficient diagnostic accuracy for differentiation between benign and malignant adrenocortical disease and lack of sensitive markers reflecting tumor load emphasize the need for novel biomarkers for diagnosis and follow-up of adrenocortical carcinoma (ACC).

DESIGN

Since the inhibin α-subunit is expressed within the adrenal cortex, the role of serum inhibin pro-αC as a tumor marker for ACC was studied in patients.

METHODS

Regulation of adrenal pro-αC secretion was investigated by adrenocortical function tests. Serum inhibin pro-αC levels were measured in controls (n=181) and patients with adrenocortical hyperplasia (n=45), adrenocortical adenoma (ADA, n=32), ACC (n=32), or non-cortical tumors (n=12). Steroid hormone, ACTH, and inhibin A and B levels were also estimated in patient subsets.

RESULTS

Serum inhibin pro-αC levels increased by 16% after stimulation with ACTH (P=0.043). ACC patients had higher serum inhibin pro-αC levels than controls (medians 733 vs 307 ng/l, P<0.0001) and patients with adrenocortical hyperplasia, ADA, or non-adrenocortical adrenal tumors (148, 208, and 131 ng/l, respectively, P=0.0003). Inhibin pro-αC measurement in ACC patients had a sensitivity of 59% and specificity of 84% for differentiation from ADA patients. Receiver operating characteristic analysis displayed areas under the curve of 0.87 for ACC vs controls and 0.81 for ACC vs ADA (P<0.0001). Surgery or mitotane therapy was followed by a decrease of inhibin pro-αC levels in 10/10 ACC patients tested during follow-up (P=0.0065).

CONCLUSIONS

Inhibin pro-αC is produced by the adrenal gland. Differentiation between ADA and ACC by serum inhibin pro-αC is limited, but its levels may constitute a novel tumor marker for ACC.

Expression of activin and inhibin subunits, receptors and binding proteins in human adrenocortical neoplasms

OBJECTIVE

The growth and differentiation factors activin and inhibin can affect tumour formation and steroid production in the adrenal cortex. These factors bind to type I (Alk-4), type II (ActRIIA, ActRIIB) and type III (betaglycan) receptors or to the activin-binding protein follistatin. Expression of these activin-related mRNAs was measured in different types of adrenocortical tissues and tumours to study the relationship with tumorigenesis.

DESIGN

Quantitative expression of activin-related mRNAs was investigated in patient adrenocortical samples.

PATIENTS

Twenty-eight human adrenocortical samples from normal and hyperplastic adrenals and from adrenocortical adenomas and carcinomas were collected after surgery for study purposes.

MEASUREMENTS

Using quantitative reverse transcription polymerase chain reaction (RT-PCR), we investigated the expression of inhibin alpha-, betaA- and betaB-subunits, follistatin, betaglycan, ActRIIA, ActRIIB and Alk-4 in the adrenocortical tissues. The expression of cytochrome P450c17 (CYP17) mRNA was also measured to investigate its association with inhibin and activin subunit expression.

RESULTS

All genes studied were expressed in all tissues, with the exception of the inhibin alpha-subunit in one hyperplastic adrenal and three adrenocortical carcinomas. Expression of inhibin betaA-subunit, follistatin, betaglycan, ActRIIA, ActRIIB and CYP17 differed between nontumorous adrenals and carcinomas.

CONCLUSIONS

These differences, together with correlation analysis, indicate parallel regulation of the expression of CYP17, the inhibin alpha-subunit, ActRIIA, ActRIIB, betaglycan and follistatin. We conclude that the expression of activin and inhibin subunits, receptors and binding proteins is affected by tumour formation in the adrenal gland and may play a role in tumorigenesis.

Effect of embryonic 19-nortestosterone treatment and surgical bursectomy on plasma concentrations of reproductive hormones, on inhibin content in adrenals and gonads and on the histological appearance of the gonads in the young chicken

Four-day-old chick embryos were hormonally treated with 19-nortestosterone in order to inhibit bursa development. At days 1, 4, 8, 15, 22, 29, and 36 of age, plasma, adrenals, and gonads from intact and hormonal treated chicks were collected. In embryonic nortestosterone treated males the appearance of a left 'ovotestis-like' gonad was observed. The occurrence of this ovotestis-like left gonad in the 19-nortestosterone treated male is probably a secondary effect of the in ovo treatment since surgically bursectomised chicks did not show the testicular morphology and histological changes as observed in 19-nortestosterone treated chicks. Additionally, both male and female hormonally or surgically treated chicks showed relatively enlarged adrenal glands. Hormonal bursectomy affected organ inhibin contents and plasma inhibin, testosterone, and FSH levels in males. Male hormonal treated chicks showed lower levels of plasma inhibin (p=0.0001), testosterone (p=0.01), and FSH (p=0.004), and a lower total testes inhibin content (p=0.0003) compared to intact chicks. However, none of these were significantly different between female intact and hormonal treated chicks, again indicating that the observed hormonal changes in males are not the result of the disappearance of the bursa but of the hormonal 19-NT treatment. The total adrenal inhibin content as well as the adrenal inhibin concentration were significantly higher in hormonally treated chicks than in intact chicks (p=0.0001), regardless of the sex.

Expression of activin/inhibin receptor and binding protein genes and regulation of activin/inhibin peptide secretion in human adrenocortical cells

Activins and inhibins are glycoprotein hormones produced mainly in gonads but also in other organs. They are believed to be important para/autocrine regulators of various cell functions. We investigated activin/inhibin receptor and binding protein gene expression and the regulation of activin/inhibin secretion in human adrenal cells. RT-PCR revealed inhibin/activin alpha-, betaA/B-subunit, follistatin, activin type I/II receptor, and inhibin receptor (betaglycan and inhibin-binding protein) mRNA expression in fetal and adult adrenals and cultured adrenocortical cells. Cultured cells secreted activin A and inhibin A/B as determined by specific ELISAs. ACTH stimulated inhibin A/B secretion in fetal (1.8- and 1.8-fold of control, respectively) and in adult cells (3.4- and 1.7-fold of control, respectively) without significant effect on activin A. 8-bromoadenosine cAMP (protein kinase A activator) increased activin A and inhibin A/B secretion in the human adrenocortical NCI-H295R cell line (32-, 17-, and 3-fold of control, respectively). 12-O-tetradecanoyl phorbol-13-acetate (protein kinase C activator) stimulated both activin A and inhibin A secretion (764- and 32-fold of control, respectively), and activin treatment increased inhibin B secretion in these cells (25-fold of control). In conclusion, human adrenocortical cells produce dimeric activins and inhibins. ACTH stimulates inhibin secretion and decreases activin/inhibin secretion ratio, probably via the protein kinase A signal transduction pathway. This, together with the adrenocortical activin/ inhibin receptor and binding protein expression, suggests a physiological role for activins and inhibins in the human adrenal gland.

The human homolog of Diminuto/Dwarf1 gene (hDiminuto): a novel ACTH-responsive gene overexpressed in benign cortisol-producing adrenocortical adenomas

To elucidate the molecular mechanism of the pathogenesis of benign functioning adrenocortical adenomas causing Cushing's syndrome, we employed suppression PCR-based cDNA subtractive hybridization to identify novel genes that are differentially expressed in the adenoma. In this report we describe the adenoma-specific overexpression of the human homolog of the Diminuto/Dwarf1 (hDiminuto) gene. Northern blot analysis revealed that hDiminuto mRNA was overexpressed in the adenoma tissue of 14 patients with Cushing's syndrome in comparison to the adjacent nontumorous adrenal gland. In situ hybridization using hDiminuto cRNA probe showed its abundant expression in the tumor cells, whereas the nontumorous cells showed a low level of expression. As the atrophic adjacent gland may not represent the normal architecture, we examined the expression pattern of hDiminuto mRNA in normal human adrenal cortex. In situ hybridization revealed that it was expressed in all layers of the normal adrenal cortex. In situ apoptosis detection by the TUNEL method revealed that a low level of hDiminuto expression in the atrophic, adjacent gland was associated with numerous TUNEL-positive cells in all layers of cortex. In contrast almost no apoptotic cell was detected in the tumor or in the normal adrenal cortex where hDiminuto expression was abundant. These results are compatible with a recent report that hDiminuto acts as an antiapoptotic factor in neurons. The expression of hDiminuto in the normal adrenal cortex was most abundant in the zona fasciculata, suggesting its possible regulation by ACTH/cAMP. Indeed, forskolin treatment of H295R human adrenocortical cells resulted in a significant induction of the mRNA in a time- and dose-dependent manner. To further demonstrate the physiological regulation, an in vivo experiment was carried out in dexamethasone-treated rats. ACTH administration to these rats increased the mRNA expression. These results led us to speculate that the overexpression of hDiminuto in the adenoma could be due to the abundant expression of ACTH receptor, as we previously described. Diminuto is involved in steroid synthesis and cell elongation in plants. We, therefore, hypothesize that hDiminuto might be involved in the molecular events of adrenocortical tumorigenesis by facilitating steroid synthesis and cell growth.

Immunoexpression of inhibin alpha-subunit in adrenal neoplasms

Inhibin normally is produced by ovarian granulosa cells and testicular Sertoli cells. Extragonadal inhibin expression also has been detected in the placenta, pituitary gland, and liver. It may be difficult to make a distinction between adrenal cortical tumors, pheochromocytoma, and metastatic carcinomas including renal cell and hepatocellular carcinoma. Immunohistochemical expression of inhibin alpha-subunit was evaluated to determine whether any usefulness of immunostaining could be found for inhibin alpha-subunit in the differential diagnosis of adrenal glandular lesions. The authors performed immunostaining against inhibin alpha-subunit on 5 cases of normal adrenal gland, 1 case of adrenal cortical hyperplasia, 25 cases of adrenal cortical adenoma, 6 cases of adrenal cortical carcinoma, 21 cases of pheochromocytoma, 8 cases of metastatic carcinoma, and 10 cases of primary renal cell carcinoma. Normal adrenal gland showed a strong immunoreactivity against inhibin alpha-subunit, especially in the inner layer of the adrenal cortex, representing the zona reticularis, but adrenal medulla was negative for inhibin alpha-subunit. Adrenal cortical hyperplasia associated with Cushing's syndrome showed a strong, diffuse immunoreactivity for inhibin alpha-subunit. Immunoreactivity against the inhibin alpha-subunit was identified in all cases of adrenal cortical adenoma and carcinoma, especially in the adrenal cortical neoplasm with Cushing's syndrome, which showed a strong reactivity. However, immunoreactivity was absent in two metastatic carcinomas from the liver and colon and most of the pheochromocytomas, except three cases with weak focal positivity for inhibin alpha-subunit. Four cases of metastatic renal cell carcinoma and 10 cases of primary renal cell carcinoma revealed no immunoreactivity. Metastatic adenocarcinoma from the prostate showed a weak immunoreactivity for inhibin alpha-subunit. Metastatic hepatoblastoma was negative against inhibin alpha-subunit with endogenous biotin blocking. Immunoexpression for inhibin alpha-subunit is useful for making distinction between adrenal cortical tumors, pheochromocytoma, and metastatic carcinoma. Inhibin alpha-subunit may be valuable as part of a diagnostic immunohistochemical panel in adrenal glandular lesions.

Myxoid neoplasms of the adrenal cortex: a rare histologic variant

The myxoid variant of adrenocortical carcinoma is a rare neoplasm described previously in only two case reports. Because of the rarity of these lesions, the presence of myxoid changes in adrenal cortical neoplasms usually raises the possibility of malignancy. We studied the histopathologic features of 14 cases of myxoid adrenocortical neoplasms, including six adenomas and eight carcinomas. All patients with adenomas with sufficient follow-up (n = 5) were alive with no recurrence of their tumors or evidence of metastatic disease. Four patients with carcinomas died of their disease, two were alive with metastatic disease, and one was alive with no evidence of recurrence or metastatic disease. Histologically, the 14 tumors varied in their myxoid composition, ranging from 10% to 95%. The myxoid foci stained positively with Alcian blue and were usually negative with periodic acid-Schiff and mucicarmine stains. As a group, the immunophenotype of the lesions was typical of other adrenal cortical neoplasms, with positive immunostaining for vimentin, synaptophysin, and alpha-inhibin. One tumor was focally positive for keratin. Myxoid adrenal cortical neoplasms should be included in the differential diagnosis of myxoid retroperitoneal neoplasms. Myxoid changes in adrenal cortical neoplasms may be present in both adenomas and carcinomas, and the usual clinical and histopathologic features for adrenocortical neoplasms should be used to diagnose these neoplasms.

Expression of inhibin alpha in the human adrenal gland and adrenocortical tumors

We studied the expression of inhibin alpha-subunit in normal and hyperplastic adrenal glands, as well as in various adrenocortical tumors. The protein expression of inhibin alpha was performed by immunohistochemistry. Virilizing adenomas showed strong immunoreactivity against monoclonal inhibin alpha-subunit antibody, whereas other adenomas were only weakly positive or completely negative. In the adrenal cortex no inhibin alpha immunoreactivity was detected in the zona glomerulosa. Zona fasciculata showed weak staining for inhibin alpha, however, strong immunostaining was detected in zona reticularis both in normal and hyperplastic adrenal glands. Adrenal medulla was negative for inhibin alpha. In conclusion, we show high expression of inhibin alpha subunit in zona reticularis of normal and hyperplastic adrenal glands as well as strong expression in virilizing adenomas.

Immunohistochemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin

AIMS

To investigate the immunohisto-chemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin. Also, to determine whether immunostaining with this antibody is useful in differentiating between adrenal cortical neoplasms and other tumours involving the adrenal gland that might mimic them.

METHODS

Normal adrenal tissue (n = 20) and specimens from cases of adrenal hyperplasia (n = 13), adrenal cortical adenoma (n = 15), adrenal cortical carcinoma (n = 4), phaeochromocytoma (n = 8), and adrenal metastatic tumour (n = 7) were stained with a monoclonal antibody against the alpha subunit of human inhibin.

RESULTS

Positive staining with the anti-alpha inhibin monoclonal antibody was seen in all normal adrenal glands. Immunoreactivity was largely confined to the inner cell layers of the adrenal cortex, with no staining of the adrenal medulla. All hyperplastic adrenal glands and adrenal cortical adenomas and carcinomas were also immunoreactive. The other tumours studied were negative.

CONCLUSIONS

There is consistent immunoreactivity with the anti-alpha inhibin monoclonal antibody in normal adrenal cortex and in hyperplastic and neoplastic adrenal cortical lesions. In the normal adrenal cortex, positive staining is mainly confined to the zona reticularis. Other neoplasms involving the adrenal gland are negative. Immunohistochemical staining with anti-alpha inhibin monoclonal antibody, performed as part of a panel, may prove to be of value in the distinction between adrenal cortical carcinoma and phaeochromocytoma or metastatic tumour.

Evidence for the presence of immunoreactive inhibin in extragonadal tissues of ovariectomized ewes

Six ewes were ovariectomized to determine the immediate and long-term effects of removal of ovaries on the immunoreactive concentrations of FSH, LH and inhibin. Three months after ovariectomy, ewes were slaughtered and tissue samples of brain, pituitary, spleen, liver, perirenal fat, lung, kidney, adrenals and uterus were collected to determine the immunoreactive inhibin content. Both gonadotrophins, FSH and LH, increased significantly after ovariectomy. The increase of FSH, however, was more pronounced and remarkably faster than the changes of LH after ovariectomy. Immunoreactive concentrations of inhibin decreased sharply as early as 15 min after ovariectomy and subsequently decreased more gradually until 2 weeks after surgery. From this moment on, the level stabilized at 56% of the initial value. In control ewes, a considerable amount of immunoreactive inhibin is found in tissue samples of ovary, lung, kidney, pituitary and spleen. After ovariectomy, the level of immunoreactive inhibin decreased in spleen and lung samples while an important increase of immunoreactive inhibin is found in adrenals and pituitary. These results demonstrate a differential regulation of LH and FSH after ovariectomy and support an involvement of inhibin only in the immediate changes of FSH after ovariectomy in sheep. They further suggest that the adrenals and the pituitary may be extragonadal sources of inhibin. To explore the eventual contribution of the adrenals to circulating inhibin, dexamethasone (1.4 mg/ewe) and ACTH (200 IU/ewe) were in a following experiment injected intravenously in control and ovariectomized ewes. The lack of any effect of dexamethasone or ACTH on the plasma concentration of immunoreactive inhibin indicate that adrenal inhibin probably does not contribute to circulating inhibin.

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.

Ovarian and extraovarian sources of immunoreactive inhibin in the chicken: effects of dexamethasone

The present study investigates whether besides the ovary, extragonadal sources contribute to the total amount of immunoreactive inhibin in the plasma of the domestic hen. A comparison of the inhibin content of different organ shows that, expressed per milligram of tissue, the adrenal ranks second only to the ovarian granulosa layer. To explore the contribution of the adrenals to plasma inhibin, dexamethasone (100 micrograms/kg BW) was injected i.v. into intact, ovariectomized, and sham-operated hens. Control animals of each experimental group were injected with saline (0.9% (w/v) NaCI). Dexamethasone significantly (P < 0.05) decreased plasma inhibin concentrations in the three groups. The suppressive effect of dexamethasone in intact hens, however, was caused by a direct effect of this synthetic glucocorticoid on the gonads. Indeed, dexamethasone decreased the production of inhibin by granulosa cells in vitro and also lowered the immunoreactive inhibin concentration in ovariectomized animals. The decreased plasma inhibin concentration in ovariectomized animals is probably due to a direct effect of dexamethasone on the adrenals. Adrenal cells produced immunoreactive inhibin in vitro. The inhibin secretion by adrenal cells was significantly (P < 0.05) depressed by dexamethasone. In conclusion, the ovary is the major source of plasma immunoreactive inhibin in the laying hen. The presence of substantial amounts of immunoreactive inhibin in the adrenal, the secretion of inhibin by cultured adrenal cells, and the decreased immunoreactive inhibin in ovariectomized animals treated with dexamethasone indicate that the adrenal is a likely source of extragonadal inhibin. The nature and the role of this adrenal inhibin remain to be investigated.