Immunohistochemical colocalization of growth hormone (GH) and alpha subunit in human GH secreting pituitary adenomas

Mutations in growth hormone gene affect stability of protein structure leading to reduced growth, reproduction, and milk production in crossbred cattle-an insight

The GH has a multifaceted role in growth, reproduction, and milk production. Nonsynonymous mutations identified as L153V were observed from GH1 (L) to GH2 (V) with higher genotypic frequency for GH1 being 0.87. GH2 (V) allele was identified as a rare allele and the population followed Hardy-Weinberg equilibrium. LL homozygote variant had significantly better growth, reproduction, and expected milk production at different ages in crossbred (CB) males. Reports are scanty explaining the molecular mechanism of how individuals with LV genotype were phenotypically inferior to that of wild-type LL. In the present study, it was explored that GH peptide with LV heterozygotes of GH gene, were observed to have reduced structural stability thermodynamically and thus functionally leads to reduced economic traits in CB animals. The fact was first time reported and confirmed through genomic analysis, bioinformatics, and later confirmed through immunohistochemistry. Differential expression analysis of the GH gene with respect to other genes in the hypothalamus-pituitary growth axis of CB cattle was also studied to have a complete insight of the GH gene.

An analysis of granulation patterns, MIB-1 proliferation indices and p53 expression in 101 patients with acromegaly

BACKGROUND

Despite the wide spectrum of adenoma behavior in patients with acromegaly, the ability of most pathological markers to predict clinical and radiological behavior remains controversial. The authors sought to comprehensively examine clinical and radiological correlates of growth hormone (GH)-secreting pituitary adenomas with regard to several commonly used immunocytochemical techniques in patients undergoing transsphenoidal surgery for acromegaly.

METHOD

We performed a retrospective review of histopathological findings in 101 surgically resected GH adenomas. Tumors were assessed radiologically for different patterns of extension. Each tumor specimen was subject to immunocytochemical analysis, including assessments of granulation patterns, MIB-1 labeling indices, prolactin cosecretion, p53 expression and mitotic activity. Endocrinological outcome was assessed in 93 patients, with remission defined by the 2010 consensus criteria.

RESULTS

Most tumors were macroadenomas and almost half were invasive. When compared to densely granulated tumors, sparsely granulated adenomas were associated with a younger age at presentation, higher preoperative IGF-1 levels, elevated MIB-1 index and pure GH immunostaining, but did not differ significantly in terms of extrasellar invasion or outcome. Increased mitotic activity and p53 expression were also associated with higher proliferation indices and a younger age at presentation. Mixed GH/prolactin tumors demonstrated significantly higher remission rates, independent of variations in extrasellar growth. MIB-1 indices did not correlate with the preoperative GH/IGF-1 levels, adenoma size or Knosp grade.

CONCLUSION

The pathobiology of acromegaly is complex, and the clinicoradiological significance of subtyping on the basis of the markers employed in this study is debatable. Further investigation of newer molecular markers is warranted.

Epithelial splicing regulator protein 1 and alternative splicing in somatotroph adenomas

Somatotroph adenomas secrete supraphysiological amounts of GH, causing acromegaly. We have previously hypothesized that epithelial mesenchymal transition (EMT) may play a central role in the progression of these adenomas and that epithelial splicing regulator 1 (ESRP1) may function prominently as a master regulator of the EMT process in pituitary adenomas causing acromegaly. To further elucidate the role of ESRP1 in somatotroph adenomas and in EMT progression, we used RNA sequencing (RNAseq) to sequence somatotroph adenomas characterized by high and low ESRP1 levels. Transcripts identified by RNAseq were analyzed in 65 somatotroph adenomas and in GH-producing pituitary rat cells with a specific knockdown of Esrp1. The clinical importance of the transcripts was further investigated by correlating mRNA expression levels with clinical indices of disease activity and treatment response. Many of the transcripts and isoforms identified by RNAseq and verified by quantitative PCR were involved in vesicle transport and calcium signaling and were associated with clinical outcomes. Silencing Esrp1 in GH3 cells resulted in changes of gene expression overlapping the data observed in human somatotroph adenomas and revealed a decreased granulation pattern and attenuated GH release. We observed an alternative splicing pattern for F-box and leucine-rich repeat protein 20, depending on the ESPR1 levels and on changes in circulating IGF-I levels after somatostatin analog treatment. Our study indicates that ESRP1 in somatotroph adenomas regulates transcripts that may be essential in the EMT progression and in the response to somatostatin analog treatment.

Expression of MSX1 in human normal pituitaries and pituitary adenomas

Transcription factors play specific roles in the development and differentiation of normal pituitary tissues and pituitary adenoma. The transcription factor, muscle segment homeobox 1 (MSX1), which belongs to the homeobox gene family, binds the promoter region of the glycoprotein hormone alpha-subunit (SU) in TSH-producing cells in the mouse pituitary and regulates alpha-SU expression. The present study investigated MSX1 expression in the normal human pituitary. In addition, 50 pituitary adenomas were examined using immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) to clarify the role of MSX1 in the development and functional differentiation of pituitary adenoma cells. In the normal pituitary, MSX1 was predominantly expressed in the cytoplasm of GH-producing cells. Furthermore, MSX1 immunoreactivity was observed in the cytoplasm of some alpha-SU-producing cells. It is interesting to note that, in the pituitary adenoma, MSX1 was expressed in the nucleus of GH- and TSH-producing adenomas. RT-PCR using RNA extracted and purified from formalin-fixed paraffin-embedded pituitary adenoma specimens revealed MSX1 mRNA expressed in GH- and TSH-producing adenomas. Immunoelectron microscopy demonstrated MSX1 localized at intranuclear heterochromatin and euchromatin, which suggests transcriptional activity. These results suggest that MSX1 plays a specific role in human pituitary adenoma.

ACTH and alpha-subunit are co-expressed in rare human pituitary corticotroph cell adenomas proposed to originate from ACTH-committed early pituitary progenitor cells

The functional differentiation of pituitary cells and adenomas follows the combination of transcription factors and co-factors in three cell lineages [growth hormone-prolactin-thyroid-stimulating hormone lineage, adrenocorticotrophic hormone (ACTH)/pro-opiomelanocortin (POMC) lineage, and follicular stimulating hormone (FSH)/luteinizing hormone (LH) lineage], which include Pit-1, GATA-2, SF-1, NeuroD1/beta2, Tpit, ERalpha, and others. Only rarely are hormones from different lineages co-expressed in the same adenoma cells. Most corticotroph cell adenomas belonging to the ACTH/POMC lineage are mono-hormonal. In our study of 89 corticotroph cell adenomas, 5 cases expressed both ACTH and alpha-subunit; these adenomas did not express any other anterior pituitary hormones or subunits. To clarify the mechanism involved, we studied the transcription factors that regulate pituitary cell differentiation. NeuroD1 and T-pit, markers of the ACTH/POMC lineage, and SF-1 and DAX-1, related to the LH/FSH cell lineage were expressed in all cases. GATA2, a synergistic factor in the gonadotroph cell lineage with SF-1, was also expressed in three of five cases. As ACTH and alpha-subunit are the earliest hormones to appear during development, we speculate that these particular adenomas are derived from committed ACTH progenitor cells. The molecular process governing functional differentiation of these adenomas requires further investigation.

Induction of GH, PRL, and TSHβ mRNA by transfection of Pit-1 in a human pituitary adenoma-derived cell line

The functional development of pituitary cells depends on the expression of a combination of transcription factors and co-factors. Pituitary-specific transcription factor-1 (Pit-1) is required for the expression of growth hormone (GH), prolactin (PRL), and the thyroid-stimulating hormone beta subunit (TSH beta) and acts synergistically with the estrogen receptor (ER) and GATA-binding protein 2 (GATA-2) to induce PRL and TSH beta expression, respectively. The glycoprotein hormone alpha subunit (alpha SU) is the first hormone to be expressed during pituitary development. In addition to being expressed in follicle-stimulating hormone, luteinizing hormone (LH), and TSH cells, alpha SU is reported to co-localize with GH in pituitary cells. These findings have led to the suggestion that the expression of Pit-1 in cells of the alpha SU-based gonadotropin cell lineage might also lead to the expression of GH. In this study, we transfected HP 75 cells (derived from a human non-functioning pituitary adenoma that expressed alpha SU and LH beta) with Pit-1 by using an adenovirus FLAG-Pit-1 construct. Most of the transfected cells expressed GH mRNA, with fewer cells expressing PRL and TSH beta mRNA. The HP 75 cells expressed the genes for ER and GATA-2, thus allowing their expression of GH, PRL, and TSH beta mRNA in response to Pit-1. These results support the hypothesis that GH can be induced in cells that possess an active alpha SU gene and shed light on the basic molecular mechanism that drives the development of GH, PRL, and TSH beta expression in the alpha SU-based gonadotroph lineage.

Hormone markers in pituitary adenomas: changes within last decade resulting from improved method

The significance of polyclonal antibodies for demonstration of hormone expression in pituitary adenomas was compared with the significance of monoclonal antibodies (MAbs). Adenomas were classified by light microscopic structures in paraffin- and epon-embedded sections, by immunostaining for all pituitary hormones, and in part by electron microscopy. In the first series, 166 adenomas were studied with polyclonal antibodies during 1990 and 1991. In the second series, 572 adenomas were immunostained with MAbs during 1999 and 2000. In the first series, a very typical type-specific hormone expression was demonstrable in 63.2% of adenomas in contrast to 91.1% in the second series. Consequently, in the first series 36.7% of adenomas expressed additional or atypical hormones in >10% of adenoma cells, whereas in the second series only 8.9% contained additional hormones. We conclude that MAbs show a clearer cutoff in immunostainings of pituitary hormones and therefore should be preferred for adenoma classification.

Serum alpha-subunit levels in patients with pituitary adenomas

OBJECTIVE

We investigated preoperative and postoperative serum alpha-subunit levels and the alpha-subunit response to TRH in patients with various types of pituitary tumour and correlated the data with histological findings in order to clarify the significance of alpha-subunit measurement in pituitary adenomas.

PATIENTS

We examined 59 patients with pituitary tumours (22 with GH cell adenomas, 30 with clinically nonfunctioning adenomas and seven with other tumours) treated at Toranomon Hospital between 1996 and 1998.

RESULTS

The basal alpha-subunit level was supranormal in six out of 22 (27%) patients with a GH cell adenoma and in nine out of 30 (30%) patients with a nonfunctioning adenoma. A paradoxical alpha-subunit response to TRH was found in seven out of 22 (32%) patients with a GH cell adenoma. These seven patients also showed a paradoxical GH response to TRH administration. In addition, paradoxical response to TRH was found in eight out of 30 (27%) patients with a clinically nonfunctioning adenoma. In contrast, patients with other types of pituitary tumour showed neither a supranormal alpha-subunit level nor a paradoxical response to TRH. The supranormal alpha-subunit level and the abnormal response to TRH were normalized in both GH cell adenoma and nonfunctioning adenoma patients after successful surgery. Immunohistochemical studies showed alpha-subunit positive cells in 51% of GH cell adenomas or nonfunctioning adenomas and there was a good concordance with the serum alpha-subunit levels in both GH cell adenoma and nonfunctioning adenoma patients.

CONCLUSIONS

These findings suggest that supranormal serum alpha-subunit levels are mainly due to hypersecretion by the tumour itself, while the paradoxical alpha-subunit response to TRH is an associated phenomenon in patients with a GH cell adenoma or nonfunctioning adenoma. The alpha-subunit level and the response to TRH may be useful indicators for assessing the operative outcome, especially in nonfunctioning adenoma patients who have no other definite endocrine markers.

Pituitary adenomas in acromegaly: Comparison of different adenoma types with clinical data

Adenoma tissues from 309 patients with active acromegaly was examined by routine light microscopy and immunohistochemistry, and selectively by electron microscopy. All adenomas were immunoreactive for growth hormone. Eighty-seven adenomas were monohormonal (28%), 58 were bihormonal (immunoreactive for growth hormone and prolactin) (19%), and 157 adenomas were plurihormonal (51%), with positivity for glyco-proteins and/or their α-subunit as well. The mean tumor size was significantly greater in monohormonal adenomas than in other adenoma types. There was no difference in invasiveness among the various adenoma types. Younger patients showed invasive tumor growth more often. Patients with densely granulated GH cell adenomas had a significantly longer duration of symptoms compared to patients with other adenoma types. More than half of the patients with sparsely granulated GH cell adenomas had a duration of less than 5 yr. There was no correlation between duration of symptoms and tumor size. The preoperative mean GH level was significantly higher in patients with sparsely granulated GH cell adenomas than in those with mixed GH/PRL cell adenomas. The preoperative mean PRL level was significantly higher in patients with bihormonal adenomas than in those with plurihormonal adenomas. There was an inverse correlation between age and preoperative GH and PRL levels. No linear correlation was found between preoperative basal GH and PRL levels. Monohormonal adenomas presented more often with suprasellar and/or parasellar extension than other adenoma types. Our data suggest a positive correlation between tumor extension and preoperative GH and PRL levels. Patients with plurihormonal adenomas were significantly older than patients with sparsely granulated GH cell adenomas and mixed GH/PRL cell adenomas. No significant difference was found between the various adenoma types and the extent of surgical removal, which depends on the degree of invasiveness, tumor size, and extrasellar tumor extension.

Immunohistochemical detection of glycoprotein hormone alpha subunit in somatoprolactinic and pure somatotroph adenomas

Glycoprotein hormone alpha subunit (alpha SU) is expressed in nearly all thyreotroph adenomas and most gonadotrophinomas, but is less well documented in plurisecreting adenomas. We therefore examined the immunohistochemical (IHC) expression of alpha SU in a generally accepted model of plurisecreting adenomas (somatoprolactinic type) by comparison to a series of pure monosecreting somatotroph tumors. Fifty patients (32 females, 18 males) aged 15 to 68 years with clinical and/or biological acromegaly requiring adenomectomy were studied. Forty-five had clinical acromegaly and 5 had isolated amenorrhea and/or galactorrhea syndromes. Forty-eight of the 49 patients who had baseline assessments of plasma GH had a mean concentration of 5 ng/ml or more (normal value < 5). Fifteen of the 46 patients who had baseline measurements of plasma PRL had a prolactinemia value greater than 20 ng/ml (normal value < 20) but below 100 ng/ml, except for one patient. All the adenomas studied were positive by GH immunohistochemistry; 21 were immunostained by an antiPRL antibody and formed the "somatoprolactinic" (GH-PRL) group. Five of these 21 patients were male. The 12 female patients younger than 50 years had amenorrhea or galactorrhea, and one male patient complained of impotence. Eleven patients (9 females, 2 males) in this GH-PRL group had hyperprolactinemia. Sixteen of these GH-PRL adenomas were immunolabeled by alpha SU antiserum. The remaining 29 adenomas, which were immunonegative with the PRL antibody and formed the "somatotroph adenoma" (GH) group, were more frequent in male patients (13/29; 45%) compared to GH-PRL group. Eight amenorrhea or galactorrhea syndromes occurred among the 14 women younger than 50 years, 3 of whom had hyperprolactinemia. Thirteen of these 29 adenomas (45%) were immunopositive with alpha SU antibody. Compared to the GH group, the GH-PRL group had a significant higher frequency of amenorrhea and/or galactorrhea syndromes among women under 50 years (100% vs 57%; p < 0.01), as well as hyperprolactinemia (55% vs 15%; p < 0.01) and positive alpha SU immunoreactivity (76% vs 45%; p < 0.05). The frequency of extrasellar macroadenomas was not different according to PRL or alpha SU immunoreactivity. Thus, in this series of somatoprolactinic adenomas, alpha SU immunopositivity was slightly more frequent than in a control group of pure somatotroph adenomas. Moreover, hyperprolactinemia was more frequent in patients with GH-PRL adenomas, although the size of the pure and mixed adenomas was not different. These results suggest that hyperprolactinemia and/or alpha SU immunopositivity are more often associated with mixed GH-PRL adenomas.

Production and characterization of specific anti-peptide antiserum against free alpha-subunit of rat pituitary glycoprotein hormones

To obtain an antibody specific for the alpha-subunit of rat pituitary glycoprotein hormones, we synthesized a peptide corresponding to the sequence 37-53 (ST-7: Phe-Ser-Arg-Ala-Tyr-Pro-Thr-Pro-Ala-Arg-Ser-Lys-Lys-Thr-Met-Leu-Val) of the rat alpha-subunit. The polyclonal antiserum against this peptide was generated in rabbits. This region is hydrophilic and highly conserved among several mammalian species. Noncompetitive binding tests showed that the ST-7 antiserum had specific affinity for the rat free alpha-subunit, but not for rat intact LH, FSH, and TSH. The ST-7 antiserum immunostained two types of cells in the rat anterior pituitary, i.e., gonadotrophs and thyrotrophs. This was also the case in mouse, cattle, sheep, and pig, which have an identical sequence of ST-7 in their alpha-subunit. The pituitary cells of horse (Arg substituted for Lys as residue 48 of the rat alpha-subunit), human, and eel (Leu for Ala at residue 45), chicken (Met for Ala at residue 45), and bullfrog (Tyr for Phe at residue 37 and Met for Ala at residue 45) were not stained with the ST-7 antiserum. This study indicated that the ST-7 antiserum is sequence-specific for the alpha-subunit and is therefore useful for immunohistochemical studies on the secretory pathway of the free alpha-subunit.

Evidence for a trophic action of the glycoprotein hormone alpha-subunit in rat pituitary

The effect of the alpha-subunit of luteinizing hormone (LH alpha) on lactotroph growth in 14-day-old rat pituitary was studied in vitro using a reaggregate pituitary cell culture system. LH alpha significantly expanded both the total population of cells expressing prolactin mRNA and the number of [3H]thymidine incorporating prolactin mRNA expressing cells. No such effect could be elicited by LH. Both effects were inhibited by simultaneous addition of an anti-LH alpha antiserum but not by normal rabbit serum. Anti-LH alpha antiserum added alone to the cultures caused a small decrease in the number of prolactin mRNA expressing cells and in [3H]thymidine labelling of the latter. It is concluded that LH alpha may be a trophic factor of lactotrophs not only during fetal development, as suggested by others previously, but also during the rapid expansion of this cell type during postnatal life in the rat.

Colocalization of growth hormone (GH) and glycoprotein subunit alpha in GH-producing pituitary adenomas in acromegalic patients

Thirty-one consecutive cases of pituitary adenoma in acromegalic patients were studied by immunohistochemistry. All adenomas contained cells immunoreactive with the anti-alpha-subunit of gonadotropic hormones (alpha; 0.6-53% of tumor cells) as well as with anti-growth hormone (GH; 4-74% of tumor cells). In serial section study, most cells immunoreactive with anti-alpha were identical to cells immunoreactive with anti-GH. There was a positive correlation between the percentages of cells immunoreactive for alpha in GH cells [alpha (%)/GH(%)] and those for prolactin (PRL) in immunoreactive tumor cells (PRL(%)/[PRL(%) + GH(%)]) in mixed GH cell-PRL cell adenomas, suggesting that the alpha-subunit may play a role in emergence of PRL cells.

Immunohistochemical expression of Pit-1 protein in human pituitary adenomas

Pit-1, the pituitary-specific transcriptional factor, has been known as a gene that regulates the functional differentiation of the anterior pituitary gland, especially in GH, PRL, and TSH production. Our immunohistochemical studies were performed to elucidate the functional roles of the pit-1 product in human pituitary adenomas. Eighty-six pituitary adenomas consisted of 51 GH-producing adenomas, 18 nonfunctioning (NF) adenomas, 1 1 PRL adenomas, and 6 TSH adenomas. Indirect immunoperoxidase method was performed using antibodies against GH, PRL, ACTH, the α subunit (SU), FSH β-SU, LH β-SU, TSH β-SU, and pit-1 product. Pit-1 product was expressed in 38 patients in the nuclei of the adenoma cells. The frequency of positive pit-1 product was significantly high in the patients with TSH and GH adenomas compared with those who had NF adenomas. These results suggest a role for pit-1 in functional differentiation of the human pituitary adenomas, especially TSH and GH adenomas.

Growth hormone-producing pituitary adenomas: correlations between clinical characteristics and morphology

In this study, we compared the clinical and endocrinological characteristics, neuroimaging findings, surgical outcome, and conventional histological findings (including immunohistochemistry) with the electron microscopic appearance of 31 growth hormone (GH)-producing adenomas. By electron microscopy, these 31 tumors were divided into 23 densely granulated somatotroph adenomas (DG adenomas) and 8 sparsely granulated somatotroph adenomas (SG adenomas). SG adenomas more frequently affected younger women, but no significant correlation was found between the adenoma type and the characteristic signs and symptoms of acromegaly, the incidence of diabetes mellitus or hypertension, or the basal serum GH and insulin-like growth factor I levels. A distinct response of GH to thyrotropin-releasing hormone, bromocriptine, or GH-releasing hormone was significantly more common in patients with DG adenomas than in those with SG adenomas, whereas the incidence of a response to gonadotropin-releasing hormone or oral glucose was not significantly different between the two groups. An analysis of neuroimaging findings and surgical results indicated that SG adenomas were more likely to be macroadenomas with suprasellar extension or invasive tumors and had a lower surgical cure rate. However, postoperative radiotherapy seemed to be similarly effective in both types of adenoma to prevent a tumor recurrence and to reduce postoperative GH basal level in serum. Light microscopy showed that DG adenomas were mainly acidophilic and were immunopositive not only for GH but also for prolactin (43%), the beta subunit of thyroid-stimulating hormone (26%), and the alpha subunit of glycoprotein hormone (87%), whereas SG adenomas were almost all chromophobic and only revealed immunopositivity for GH.(ABSTRACT TRUNCATED AT 250 WORDS)

Mixed growth hormone cell- prolactin cell pituitary adenoma with acromegaly: α-subunit most growth hormone cells

A 51 -year-old woman with mixed growth hormone (GH) cell-prolactin (PRL) cell pituitary adenoma is presented. She had clinical signs due to hypersecretion of GH and PRL. Resected tissue was studied immunohistochemically and morphologically. The serial sections revealed that GH and α-subunit were co-localized in most cells, while GH and PRL were localized in different cells.

The alpha-subunit of glycoprotein hormones exists in the prolactin secretory granules of the bullfrog (Rana catesbeiana) pituitary gland

Our recent finding that the number of immunoreactive alpha-subunit cells was invariably greater than the total number of immunoreactive gonadotropin (GTH) and thyrotropin (TSH) cells in the bullfrog (Rana catesbeiana) pituitary gland raises the possibility that the alpha-subunit also exists in pituitary cells other than GTH and TSH cells. The present study demonstrates that there are a considerable number of immunoreactive prolactin (PRL) cells that are also stained with antibody against the alpha-subunit when adjacent sections are immunocytochemically examined. Neither immunoreactive growth hormone nor adrenocorticotropin cells are stained with the antibody against the alpha-subunit. The specificity of the antibody against the alpha-subunit and of that against PRL was demonstrated by preabsorption test, non-competitive binding test, and immunoblot analysis. Double-immunolabeling with gold particles of different sizes for the alpha-subunit and PRL revealed that most of the immunolabeled PRL-secretory granules are also labeled with the alpha-subunit antibody. The gold particles indicating the presence of the alpha-subunit were mostly found in the peripheral zone of the secretory granules.

Ultrastructural diagnosis of human pituitary adenomas

Electron microscopy, which has been instrumental in the characterization of normal pituitary cell types, has also played a crucial role in the morphologic classification of pituitary adenomas arising in the presently known 5 cell types, and in the recognition of 3 adenoma types with yet undisclosed cell derivation. This review deals with the application of electron microscopy for study of pituitary adenomas in order to provide specific pathological diagnosis and aid the clinician in selecting appropriate postoperative treatment. In addition to the ultrastructural appearance and diagnostic features of 15 adenoma types, the morphology of hyperplastic proliferations and that of known normal counterparts of various adenoma types are also discussed. Specific morphologic diagnosis of pituitary lesions is important not only for adequate postoperative management of patient, but is also a prerequisite for study of the natural history and biological behaviour of various adenoma types.

Folliculostellate cells in pituitary adenomas: Studies of hormonal profile and tumor vascularity

The hormonal immunoreactivity and vascularity of pituitary adenomas containing folliculostellate (FS) cells have been compared with those of tumors in which such cells were not identified. FS cells were present in variable numbers in 36 of 92 tumors. Adenomas immunoreactive for growth hormone (GH), adrenocorticotropic hormone (ACTH), or prolactin (PRL) contained FS cells in 40-50% of cases. Those immunoreactive for glycoprotein hormones and alphasubunit contained FS cells in 67-85% of cases, a statistically significant correlation. When alpha-subunit was also present in GH-, GH/PRL-, and ACTH-immunoreactive tumors, a higher proportion contained FS cells (57-91%). These data suggest a correlation between the presence of FS cells and glycoprotein immunoreactivity in pituitary adenomas. Vascular channels identified by the binding of the lectinUlex europaeus were quantified in the two types of tumors. Those containing FS cells were not more vascular than those without FS cells, which suggests that FS cells do not play a significant role in the regulation of intratumoraf vascularization in human pituitary adenomas.

Differential appearance of the subunits of glycoprotein hormones (LH, FSH, and TSH) in the pituitary of bullfrog (Rana catesbeiana) larvae during metamorphosis

The ontogeny of gonadotrophs and thyrotrophs in the bullfrog pituitary was examined immunohistochemically using monoclonal antibodies against bullfrog lutropin beta-subunit (LH beta), follitropin beta-subunit (FSH beta) and its alpha-subunit, and polyclonal anti-human thyrotropin beta-subunit (TSH beta) serum. Immunoreactive alpha-subunit- and TSH beta-, but not FSH beta- and LH beta-containing cells were observed at embryonic stage 24 (Shumway's classification). Immunoreactive FSH beta cells first appeared at Taylor-Korllos stage V, and immunoreactive LH beta cells at stage X. Throughout metamorphosis, several gonadotrophs containing both FSH and LH were found in the ventrocaudal region, but most gonadotrophs contained only FSH. Immunoreactive alpha-subunit cells were always more frequent than the sum of immunoreactive beta-subunit cells, which was confirmed by quantitative studies using immunohistochemical and RIA techniques.

Application of preembedding immunohistochemistry in the study of adenohypophysial plurihormonality

An immunoelectron microscopy preembedding technique has been utilized as a method which enables the observation of various bioactive substances in various intracellular organelles. In this review article, the observations made by preembedding immunoelectron microscopy describe plurihormonal pituitary cell emphasizing subcellular localization of hormones and their alterations.

Expression of glycoprotein hormones and intracytoplasmic distribution of cytokeratin in growth hormone-producing pituitary adenomas

Sixteen growth hormone (GH)-producing pituitary adenomas were studied for the expression of glycoprotein hormone subunits and cytokeratin by light microscopic immunohistochemistry. Cytokeratin immunoreactivity was demonstrated in all adenomas, but its intracytoplasmic distribution showed two distinct patterns; a prominent, dot-like pattern and a diffuse, perinuclear pattern. Seven adenomas (type 1) were exclusively composed of cells with cytokeratin in a dot-like pattern, whereas 9 adenomas (type 2) comprised of cells with cytokeratin of perinuclear distribution. The expression of alpha-subunit of glycoprotein hormone was significantly different between the two types of adenomas; 8 of 9 adenomas of type 2 contained many alpha-subunit immunoreactive cells but none of type 1 adenomas showed any immunoreactivity. Only a small number of adenoma cells were positive for beta-subunit of thyrotropin stimulating hormone in 3 adenomas of type 2. beta-subunits of follicle stimulation hormone and luteinizing hormone were negative in all adenomas. These findings suggest that the expression of glycoprotein hormone subunits in GH-producing adenomas may be closely linked to their types distinguishable by the cytokeratin distribution pattern.

Immunoreactive luteinizing hormone in functioning corticotroph adenomas of the pituitary. Immunohistochemical and tissue culture studies of two cases

Two pituitary adenomas removed from a 37-year-old woman and a 26-year-old woman with typical Cushing's disease were studied by light and electron microscopy, immunohistochemistry and radioimmunoassay of tissue culture media. Both patients had high plasma levels of cortisol and normal levels of luteinizing hormone (LH). Both tumours were monomorphous, composed of densely granulated corticotrophs; the tumour cells contained periodic acid-Schiff positivity, were arranged in a sinusoidal pattern and, ultrastructurally, contained well-developed cytoplasmic organelles. By immunohistochemistry the majority of tumour cells contained immunoreactive adrenocorticotropin (ACTH); approximately 10% of the tumour cell population contained LH immunoreactivity. The LH-positive cells tended to form clusters scattered widely throughout the tumour tissues. LH immunoreactivity was demonstrated in some ACTH-immunoreactive cells on serial sections. Large amounts of immunoreactive ACTH and smaller quantities of LH, follicle stimulating hormone and alpha-subunit were released into the culture media and release of the glycoprotein hormones responded in parallel to corticotropin releasing hormone stimulation or inhibition by cortisol. These findings indicate that LH can be simultaneously produced and released by ACTH-producing tumour cells of otherwise typical functioning corticotroph adenomas. The capacity for LH production may be acquired during neoplastic proliferation. This is the first detailed report of concurrent production of LH by pituitary corticotroph adenomas.

Incorporation of human chorionic gonadotropin alpha-subunit into different types of granule in stomach endocrine cells. An immunoelectron microscopic study

In order to demonstrate the ultrastructural localization of the alpha-subunit of human chorionic gonadotropin (hCG) in the stomach mucosa, an immunoelectron microscopic study was performed using formalin-fixed specimens. In pyloric glands, alpha hCG-positive granules were irregular in outline, with a mean area and maximum diameter of 2,857 x 10(4) nm2 and 218.4 nm, respectively. In fundic glands, the granules had a smoother outline and were larger in both area and maximum diameter (3,943 x 10(4) nm2, 246.8 nm) than those of pyloric glands (p less than 0.001). In the atrophic fundic glands of non-antral gastritis, the alpha hCG granules showed a difference in shape; more elliptical granules appeared to be increased, as indicated by the higher value of the axial ratio (1,452) and lower value of D (1,862) (log10 area alpha D.log10 perimeter) compared with those in pyloric (1,231, 1,968) and fundic glands (1,148, 1,979) (p less than 0.001). The alpha-subunit of hCG is thus incorporated into different types of endocrine cell in pyloric and fundic glands, and the granule morphology appears to differ in hyperplastic alpha hCG cells of non-antral gastritis.

Double-labeling immunogold electron-microscopic study of hormonal colocalization in nontumorous and adenomatous rat pituitaries

According to the one cell, one hormone theory, the pituitary gland is composed of 5 cell types which secrete 6 hormones. Recent investigations indicate that this theory must be modified, as there are some bihormonal cells containing 2 hormones, i.e., mammosomatotrophs prolactin-growth hormone (PRL-GH). This study was undertaken in order to elucidate whether other adenohypophysial cells are capable of producing 2 hormones and to demonstrate the presence of cells coexpressing PRL-GH, PRL-thyrotropin (TSH), or TSH-GH. Sixteen nontumorous and 16 adenomatous male and female Sprague-Dawley and Long Evans rat pituitaries were removed immediately after the animals were killed and processed for transmission electron microscopy and the immunogold double-labeling technique. Coexpression of PRL-GH, PRL-TSH, and TSH-GH was found in both nontumorous and adenomatous pituitaries. Double labeling was present not only in the same cell cytoplasm but also in the same secretory granules. The question of whether these double-labeled cells represent different cell populations, transitional cell types, or precursor cells requires further investigation.

Applications of immunocytochemistry to diagnostic cytopathology

Immunohistochemical technique is now successfully applied to the cytologic materials. This review article describes details of staining procedures for immunocytochemistry at both light and electron microscopic levels. The clinical application of the technique includes aspiration biopsy cytology for breast lesions, thyroid lesions, lymph nodes, the nervous system, and others. The establishment of carcinoma cells in the body fluid by the demonstration of carcinoembyronic antigen (CEA) and the establishment of specific diagnoses in small-cell or large-cell anaplastic tumors by immunocytochemistry warrants special emphasis.

Immunoelectron microscopic studies of GH and alpha subunit in GH secreting pituitary adenomas

9 of 15 cases of GH secreting adenomas showed the localization of GH and a subunit in the adenoma cells. GH and a subunit were frequently colocalized in the same adenomas. Immunoelectron microscopically, GH and a subunit were localized in secretory granules which were packed in the cytoplasm. Immunoelectron microscopic double staining (preembedding method and post-embedding method) showed colocalization of GH and a subunit in the same secretory granules. These data suggested corelease of GH and a subunit by the same secretory granules.

Immunohistochemical studies of human FSH producing pituitary adenomas

Ten FSH producing pituitary adenomas were studied immunohistochemically. 9 cases were in males, and 7 showed elevated serum FSH levels. Immunohistochemically, all cases showed the presence of alpha-subunit and FSH-beta subunits in many tumour cells. These two subunits were frequently colocalized in the same cells. However, the expression of LH-beta subunit was extremely low (1 of 10 cases exhibiting occasional LH-beta positive tumour cells), although it has been reported that FSH-beta and LH-beta subunits are colocalized in the same cells of the normal adult pituitary gland. Immunoelectron microscopically, alpha-subunits and FSH-beta were present in the secretory granules and suggested the co-release of subunits or secretion of combined form of FSH. In 7 cases, TSH-beta was positive, and in some cases, TSH-beta was colocalized in the same tumour cells which contained alpha-subunit and FSH-beta subunit. A few cases also demonstrated immunoreactivity for PRL and ACTH. Our immunohistochemical studies suggest that FSH adenomas are multihormonal and that there is abnormal gene expression in FSH cells with loss of LH-beta appearance and co-expression of TSH-beta.