Alpha and beta subunits of glycoprotein hormones in argyrophil pituitary tumors with small granule cells

Renal cell carcinoma metastatic to a pituitary FSH/LH adenoma: case report and review of the literature

Abstract Metastases to the pituitary occur more frequently in patients with widespread cancer and mainly involve the posterior lobe. A few cases of metastatic carcinoma to a pituitary adenoma have been described so far. Here, the authors present an additional case of a clear cell renal cell carcinoma (CCRCC) metastatic to a FSH/LH/α-subunit pituitary adenoma and systematically review the literature. Immunohistochemistry and electron microscopy were performed to characterize both neoplastic components at the morphological level. Moreover, it was hypothesized that expression of VEGF and of the corresponding receptor VEGFR1 could be implicated in the development of the carcinomatous metastasis within the adenoma.

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.

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.

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.

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.

Synaptophysin immunoreactivity and small clear vesicles in neuroendocrine cells and related tumours

Synaptophysin (protein p38) immunoreactivity has been detected immunohistochemically in neuroendocrine cells of the human adrenal medulla, carotid body, skin, pituitary, thyroid, lung, pancreas and gastrointestinal mucosa as well as in 87 out of 93 neuroendocrine tumours investigated, including pheochromocytomas, chromaffin and non-chromaffin paragangliomas, ganglioneuromas, pituitary adenomas, thyroid medullary carcinomas, parathyroid adenomas, lung carcinoids and neuroendocrine carcinomas, pancreatic and gut endocrine tumours and cutaneous merkelomas. Parallel ultrastructural investigation of synaptophysin-reactive cells and tumours revealed the presence, in addition to dense-cored, secretory granules, of a population of pleomorphic, small, clear vesicles resembling synaptic vesicles of nerve terminals as well as the synaptophysin immunoreactive vesicles already described in rat adrenal medullary and pituitary cells. Synaptophysin immunoreactivity showed several differences in its distribution among tumour and non-tumour endocrine cells when compared to chromogranin A immunoreactivity, a well known marker of the core of endocrine granules. Synaptophysin represents a reliable general marker of neuroendocrine cells and tumours, which may be useful in diagnostic histopathology.

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

This immunohistochemical study disclosed that 9 of 15 GH secreting pituitary adenomas contained alpha subunit positive cells. These cases also contained PRL positive adenoma cells, but LH beta was negative. Of these 9 cases, 4 cases showed occasional FSH beta containing cells, 2 of these also contained a few TSH beta positive cells. By mirror section technique, variable numbers of adenoma cells were found to contain both GH and alpha subunit. Immunoelectron microscopically, both GH and alpha subunit were localized in secretory granules which suggested their co-release from the tumour cells. The presence of GH and alpha subunit in rough endoplasmic reticulum indicated their active production in the tumour. In the normal adult anterior pituitary gland, about 10% of GH cells contain FSH alpha, beta and LH beta subunits and had appearances suggesting the co-production of GH and FSH as well as LH. The colocalization of GH and FSH alpha is considered to be associated with the neoplastic transformation GH cells which possess the intrinsic potentiality of differentiation toward alpha subunit. However, the mechanism for the lack or deficiency of beta subunits in the neoplastic condition remains to be further investigated.

Alpha-subunit-producing pituitary adenomas. Immunocytochemical and ultrastructural studies

Immunohistological techniques demonstrate the alpha-subunit of glycoprotein hormones in the majority of endocrine-inactive, undifferentiated pituitary adenomas and pituitary oncocytomas. In about one-fifth of endocrine-active adenomas, the alpha-subunit is produced in combination with either adrenocorticotropic hormone or prolactin, and it is found in combination with growth hormone in about half of those adenomas causing acromegaly. Pure alpha-subunit-producing, endocrine-inactive adenomas characteristically have small secretory granules that are destroyed by direct osmium fixation, but are well preserved after prefixation with glutaraldehyde. As only a few atypical prolactinomas show similar secretory granules, and as they display a positive reaction for the alpha-subunit only exceptionally, this ultrastructural feature can serve as a guide to differentiate such adenomas.