Distribution of growth hormone and prolactin in secretory granules of the normal and neoplastic human adenohypophysis

Expression of p53, Ki-67 and c-erb B2 in growth hormone-and/or prolactin-secreting pituitary adenomas

The subcellular events implicated on the formation and behavior of pituitary adenomas are not fully understood. In this study we investigated the presence of p53, Ki-67 and c-erb B2 in 38 pituitary adenomas with immunohistochemical positivity for GH and prolactin (n=26; 68.4%), for prolactin (n=9; 23.7%) and for GH (n=3. 7.8%). The analyses revealed the following results: 24 (63.2%) tumors expressed variable positivity for c-erb B2, 11 (28.9%) expressed p53 positivity and 11 (28.9%) tumors were variably positive for Ki-67. Our results demonstrated a high percentage of GH/prolactin-, prolactin- and GH-secreting tumors with immunohistochemical positivity for c-erb B2. Once this membrane receptor is related to growth factors EGF and TGFalpha and both have a definite effect on tumor growth, our data suggest a possible role for c-erb B2 on the evolution of these tumors.

Mitogen-activated protein kinase activation by stimulation with thyrotropin-releasing hormone in rat pituitary GH3 cells

We examined whether mitogen-activated protein (MAP) kinase is activated by thyrotropin-releasing hormone (TRH) in GH3 cells, and whether MAP kinase activation is involved in secretion of prolactin from these cells. Protein kinase inhibitors--such as PD098059, calphostin C, and genistein--and removal of extracellular Ca2+ inhibited MAP kinase activation by TRH. A cAMP analogue activated MAP kinase in these cells. Effects of cAMP on MAP kinase activation were inhibited by PD098059. TRH-induced prolactin secretion was not inhibited by levels of PD098059 sufficient to i activation but was inhibited by wortmannin (1 microM) and KN93. Treatment of GH3 cells with either TRH or cAMP significantly inhibited DNA synthesis and induced morphological changes. The effects stimulated by TRH were reversed by PD098059 treatment, but the same effects stimulated by cAMP were not. Treatment of GH3 cells with TRH for 48 h significantly increased the prolactin content in GH3 cells and decreased growth hormone content. The increase in prolactin was completely abolished by PD098059, but the decrease in growth hormone was not. These results suggest that TRH-induced MAP kinase activation is involved in prolactin synthesis and differentiation of GH3 cells, but not in prolactin secretion.

The multihormonal character of pituitary adenomas: immuno-electron microscopic studies

This study investigates the multihormonal character of pituitary adenomas at the ultrastructural level. The growth hormone (GH)- and prolactin (PRL)-secreting adenomas under study consisted of many moderately or densely granulated cells and a few sparsely or slightly granulated cells. The GH-secreting adenomas showed well-developed cytoplasmic organelles and many large (250 nm or more) or medium-sized (200 nm) secretory granules, as well as a few small (70-150 nm) secretory granules. The PRL-secreting hormones exhibited poorly or slightly developed cyto-plasmic organelles and several small secretory granules. Morphologically and antigenically, these sparsely or slightly granulated cells were similar to those of clinically non-functioning (CN-F) adenomas, which appeared identical to cells expressing little or slight immunoreaction to pituitary hormones at the light microscopic level. As well as those of CN-F adenomas, the small secretory granules of both densely and sparsely granulated cells expressed little or only slight antigenicity of various hormones. Con-comitantly showing slight or moderate antigenicity of hormones biochemically unrelated to GH or PRL, the medium-sized or large secretory granules larger than 140 or 160 nm significantly exhibited intense PRL or GH antigenicity, respectively (Fisher's exact test; P < 0.05 or 0.01). Their GH or PRL antigenicity increased as they grew larger. Showing intermediate cells between sparsely and densely granulated cells, two CN-F adenomas, however, appeared to develop into growth hormone-secreting adenomas. This study led us to conclude that pituitary adenomas may originate from sparsely granulated cells with slight biochemically unrelated hormones, and that their hormonality may be selectively activated singly or multiply in the course of their development.

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.

Identification of mammosomatotrophs in the turkey hen pituitary: increased abundance during hyperprolactinemia

We have previously reported that the hyperprolactinemia in incubating turkey hens is associated with recruitment of lactotrophs in the pituitary gland. In this study we have used double immunofluorescence and in situ hybridization histochemistry to 1) identify mammosomatotrophs in the anterior pituitary gland of egg-laying turkey hens and incubating hens, and 2) verify PRL gene expression within mammosomatotrophs by colocalizing PRL messenger RNA in GH-immunoreactive (ir) cells. The pituitaries of laying and incubating turkey hens were collected, and the midsagittal sections were dual labeled for either PRL and GH or PRL messenger RNA and GH. The plasma PRL concentrations were higher in incubating hens (231 +/- 10.6 ng/ml) than in laying hens (43 +/- 7.4 ng/ml; P < 0.01). In the midsagittal pituitary sections, mammosomatotrophs were predominantly found scattered in the caudal lobe of the anterior pituitary gland, in the ventral half of the cephalic lobe, and at the junction of cephalic and caudal lobes. In incubating hens, the proportion of mammosomatotrophs was 7.4 +/- 1.52% (mean +/- SEM) of the total number of GH-ir and/or PRL-ir cells counted, which was significantly higher (P < 0.05) than that found in laying hens (0.6 +/- 0.23%). Furthermore, PRL gene expression was observed in many GH-ir cells in the incubating hen pituitary gland. These data suggest that 1) mammosomatotrophs are present in the turkey pituitary gland, and 2) there is an increased abundance of mammosomatotrophs in the incubating turkey hen that may contribute to hyperprolactinemia.

Detection of mammosomatotroph cells and identification of the coexistence of growth hormone and prolactin within the same secretory granules in these cells using confocal laser scanning microscopy

This study was designed to examine whether mammosomatotroph cells (MS cells) can be easily detected using confocal laser scanning microscopy (CLSM) and whether the coexistence of growth hormone (GH) and prolactin (PRL) within the same secretory granule can be identified in the MS cell using CLSM. Conventional epoxy resin-embedded tissues of mixed GH- and PRL-secreting human pituitary adenomas were used for this double-labelling immunofluorescent study by CLSM. A semithin section of the tissue after plastic removal and bleaching was immunohistochemically double-stained with primary antibodies against GH and PRL, followed by secondary antibodies conjugated with Rhodamine (GH) and FITC (PRL). MS cells simultaneously showing fluorescence of both Rhodamine and FITC were easily detected by CLSM at lower magnification. At higher magnification, the coexistence of Rhodamine and FITC on the same secretory granule was identified by using a superimposed display. This finding was confirmed by immunoelectron microscopy. The CLSM technique may be useful for the study of MS cells.

Growth hormone (GH) and prolactin (PRL) gene expression and immunoreactivity in GH- and PRL-producing human pituitary adenomas

Growth hormone(GH)-producing pituitary adenomas are morphologically heterogeneous and frequently contain not only GH immunoreactivity but also variable numbers of prolactin (PRL) immunopositive cells. Paraffin sections of 59 surgically removed GH- and/or PRL-producing adenomas classified by histology, immunocytochemistry (ICC) and electron microscopy were studied using in situ hybridization (ISH) for GH and PRL mRNA and combined with ICC for the coded hormones. Somatotroph adenomas (10 densely and 10 sparsely granulated tumours) and mammosomatotroph adenomas (10 cases) contained both GH mRNA and GH immunoreactivity. In 4 densely and 4 sparsely granulated somatotroph adenomas and 4 mammosomatotroph adenomas, only GH mRNA and its product were found. In 28 cases (6 densely and 6 sparsely granulated somatotroph adenomas, 10 mixed somatotroph-lactotroph adenomas and 6 mammosomatotroph adenomas) both GH and PRL mRNA were present, although no PRL immunoreactivity was not in 2 densely granulated somatotroph adenomas. In these cases, ISH for PRL mRNA combined with GH immunostaining revealed the presence of variable numbers of mammosomatotrophs. In 9 acidophil stem cell adenomas only PRL mRNA and its product were found; one tumour expressed both GH and PRL mRNA and their products. Nine lactotroph adenomas contained only PRL mRNA and PRL immunoreactivity. The results show that GH and/or PRL mRNA content could not be correlated with ICC for coded proteins and ultrastructural features. The mammosomatotrophs were more numerous using ISH when compared with ICC. Somatotroph, mammosomatotroph and mixed adenomas are closely related and they can be considered to represent one basic tumour type originating in a cell committed to GH production. This may undergo clonal differentiation towards a mammosomatotroph and further to the lactotroph line. The results also indicate that lactotroph adenomas arise in a cell committed to PRL production. Acidophil stem cell adenomas seem to be more closely related to lactotroph cells than somatotroph.

Pituitary lactotrophs and somatotrophs in pregnancy: a correlative in situ hybridization and immunocytochemical study

Lactotroph hyperplasia is a prominent finding in the adenohypophyses of pregnant women. In order to elucidate the morphogenesis of this change, pituitaries from 16 women in various phases of pregnancy were collected at autopsy and studied by histology, immunocytochemistry and in situ hybridization. The results showed that the increase in the amount of prolactin (PRL) mRNA paralleled the progressive lactotroph hyperplasia. The presence of mitoses in PRL-immunoreactive cells provided evidence that proliferation of preexisting lactotrophs contribute to lactotroph accumulation. Growth hormone (GH) immunoreactive cells showed a marked reduction in GH mRNA indicating that GH synthesis was inhibited. In many GH-immunoreactive cells, PRL mRNA became apparent. These findings demonstrate that GH is stored following discontinuation of GH synthesis. It appears that, when PRL is secreted in excess during pregnancy, somatotrophs are recruited to produce PRL. These somatotrophs begin to express PRL mRNA, transform to bihormonal mammosomatotrophs and possibly later to lactotrophs, contributing to PRL production. Mature somatotrophs may be regarded as reserve cells in the adenohypophysis, having the potential to switch hormone synthesis and to convert to mammosomatotrophs and possibly lactotrophs.

Use of ultrastructural immunohistochemistry in human pituitary pathology

Recent advances in ultrastructural immunohistochemistry have provided insight into not only the subcellular localization of single antigens but also the colocalization of two distinct antigens in the same cellular constituent. In the field of pituitary pathology, precise identification of cell types, mechanism of processing, and dynamic intracellular transportation of hormones, as well as production of multiple hormones in the same cells of nontumorous and neoplastic adenohypophyses, have been documented by use of these techniques. The present review deals with the use of major methods for ultrastructural immunohistochemistry including pre-, post-, and non-embedding methods, particularly focusing on their application to human pituitary pathology. Problems of tissue processing and a protocol for double labeling technique using the protein A-gold complex are also described.

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.

Plurihormonal adenomas. Analysis of 62 cases

This paper deals with the cytological features of pituitary plurihormonal adenomas based on 62 cases examined by histology, immunohistochemistry, ultrastructural study and post-embedding immunogold electron microscopy, including double labeling. In GH-cell containing adenomas, there were 9 adenomas consisting of exclusively GH and PRL cells. The other 39 adenomas contained other hormones as well as GH and PRL. Other nine combinations of pituitary hormones or alpha-subunit were observed. Special emphasis was laid on the fact that a greater part of GH-producing adenomas (74% by immunostain) were PRL-producing, although the ratio of GH-cells to PRL-cells widely varied from case to case. Concerning the double labeling study on mixed GH-PRL secreting adenomas, we recognized the existence of secretory granules containing GH only, those containing PRL only, those containing both GH and PRL and those containing neither.

Homologous radioimmunoassay for bullfrog growth hormone

Antiserum against bullfrog growth hormone (fGH) was produced by immunizing rabbits with the highly purified fGH obtained from adenohypophyses of adult bullfrogs. Histological studies on bullfrog adenohypophyses revealed that the cells that immunologically reacted with the antiserum against fGH corresponded to the ones positively stained with the antiserum against rat GH. The antiserum together with fGH and 125I-fGH was employed to develop a radioimmunoassay (RIA) for fGH. Several dilutions of plasma and of pituitary homogenate of both adult and larval bullfrogs yielded dose-response curves which were parallel to the standard curve. Ovine prolactin (PRL), and growth hormone (GH); eel and salmon GHs; and bullfrog LH, FSH, TSH, PRL, and neurointermediate lobe homogenate did not react in this assay. Plasma from hypophysectomized bullfrogs had no detectable immunoreactive GH. Pituitary homogenates of Bufo japonicus, Xenopus laevis, and Cynops pyrrhogaster gave inhibition curves which did not parallel the standard. The homologous RIA for bullfrog GH thus developed was applied for the determination of plasma and pituitary GH levels in the larvae and adults. Plasma GH levels were relatively low during preclimax period and rose as metamorphosis progressed. Plasma GH concentrations were maximum in the juvenile frogs and decreased as the animals grew up. Pituitary GH concentrations also increased as metamorphosis progressed. After metamorphosis, pituitary GH concentrations declined as the frogs gained weight. There was no sex difference in plasma and pituitary GH levels in the adult.

Plurihormonality in the secretory granules of the normal human pituitary. An immunoelectron microscopic study

Normal human autopsy anterior pituitary tissue from 5 cases was embedded in LR White resin and immunolabelled using silver-enhanced 5-nm protein A gold probes. Follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), adrenocorticotrophic hormone (ACTH), growth hormone (GH) and prolactin (PRL) were immunolocalised to the level of secretory granule. A two-sided double-labelling method was used to cross-react two hormones at a time with respect to their corresponding antibodies. All possible combinations of the six pituitary hormones were tested. Plurihormonal granules were found that contained LH + FSH, LH + TSH, and FSH + TSH. Each hormone was also found in monohormonal granules. Granule diameter was significantly larger in the pluri as opposed to monohormonal granules.

Atypical endocrine granules in atypical endocrine tumor (AET) of the lung. An immunoelectron microscopic study

Highly dense granules are a hallmark for recognizing atypical endocrine tumor (AET) of the lung. We report a case of AET with many atypical neurosecretory-type granules: moderately dense granules (mean size 373.7 nm) and "target" granules with a central dense core (425.1 nm), both apparently larger than the highly dense granules (223.3 nm). Immunoelectron microscopical studies demonstrated that all three types of granule were positive for gastrin-releasing peptide (GRP), human chorionic gonadotropin alpha-subunit (hCG alpha), calcitonin or serotonin. Although the size profiles of positive granules were similar for calcitonin and hCG alpha, they were different from those of GRP or serotonin granules. The presence of atypical granules and the different size profiles of hormonal products in AET indicate that caution is required in ultrastructural evaluation of granules in lung carcinomas.

The pituitary gland in pregnancy: a clinicopathologic and immunohistochemical study of 69 cases

A histologic and immunocytochemical study of 69 autopsy-obtained pituitaries from women who died during pregnancy, after abortion, or in the postpartum period revealed an accumulation of large chromophobic to slightly acidophilic and periodic acid-Schiff-negative pregnancy cells that were immunoreactive for prolactin but not for other pituitary hormones. This increase in the number of prolactin cells was confirmed by cell counts. Thus, pregnancy cells are capable of prolactin production. The finding of mitotic figures in such cells supports the view that they arise by multiplication from preexisting prolactin cells. With use of "mirror section" techniques, no mammosomatotrophs (cells immunoreactive for growth hormone and prolactin) were identified. Hyperplasia of prolactin cells was evident at 1 month of pregnancy and gradually disappeared within several months after delivery or abortion; the process of involution seemed to be retarded in the one lactating patient investigated. In some pituitaries, the accumulation of prolactin cells was so extensive that the hyperplastic foci resembled microadenomas. Another striking change in the pituitaries of pregnant women was appreciable reduction of immunostaining of gonadotropic cells, a process that was reversible as soon as 1 month after delivery. Among the 69 pituitaries studied, 8 noninvasive microadenomas (12%) were encountered (7 contained prolactin only and 1 was plurihormonal). Prolactin-producing adenomas were no more numerous or larger than were similar tumors encountered in nonpregnant women or normal men; thus, pregnancy neither initiates formation of pituitary adenomas nor accelerates their growth. In the pituitaries that harbored prolactin-producing adenomas, massive pregnancy cell hyperplasia was evident outside the tumor; thus, prolactin production by adenoma cells did not seem to suppress the proliferation of prolactin-containing pregnancy cells.

Somatomammotrophic cells in GH-secreting and PRL-secreting human pituitary adenomas

A morphological study has been carried out on 20 GH-secreting adenomas removed from acromegalic normoprolactinemic patients, on 29 PRL-secreting adenomas removed from hyperprolactinemic patients without signs of acromegaly and on one normal human anterior pituitary gland collected at autopsy. The protein A-gold immunoelectron microscopic technique has been utilized in order to verify the presence of mixed cells producing both GH and PRL (somatomammotrophs) in these pituitary tissues. In the normal pituitary a considerable number of somatomammotrophs (15-20%) was found, thus supporting the idea that these cells are normal components of the human anterior pituitary gland. In 10 GH-secreting adenomas and in 10 PRL-secreting adenomas somatomammotrophs were present in a variable number (from 4 to 20% of the whole cell population in GH adenomas and from 1 to 47% in PRL tumors). It can be concluded therefore that these cells, largely present in all GH/PRL-secreting adenomas, can also be found in GH-secreting and PRL-secreting tumors without clinical evidence of a mixed secretion. Adenomatous somatomammotrophs displayed ultrastructural features of adenomatous somatotrophs and mammotrophs (prominent Golgi complexes, abundant rough endoplasmic reticulum, irregular nuclei). The size and the number of granules were variable. In some cells GH and PRL were stored in distinct secretory granules, in others in mixed granules or both in mixed and distinct granules, thus suggesting that in adenomatous somatomammotrophs the efficiency of the mechanisms of sorting of the two hormones varies from one cell to another.(ABSTRACT TRUNCATED AT 250 WORDS)

Mammosomatotropes: current status and possible functions

Recent studies show that mammosomatotropes-cells that secrete both growth hormone and prolactin-are common in normal pituitary tissue. It is proposed that these dual hormone secretors serve as transitional cells for the differentiation of classical mammotropes during development, and for the functional interconversion of growth hormone and prolactin secretors in adults.

Co-localization pattern of growth hormone (GH) and prolactin (PRL) within the anterior pituitary cells in the female rat and female musk shrew

By a double immunocytochemical labeling procedure, using the protein A-gold method combined with electron microscopy, the co-localization pattern of growth hormone (GH) and prolactin (PRL) was detected in the anterior pituitary cells of female rats and female musk shrews. Two types of co-localization of GH and PRL were demonstrated. First, GH- and PRL-containing secretory granules were intermixed within closely aggregated and interdigitated cell clusters that were composed of GH and PRL cells. This phenomenon was characteristically seen in pregnant rats and pregnant musk shrews. Therefore, the occurrence of an intermixture of GH and PRL granules might be related to an enhanced cellular function for PRL synthesis. In another pattern of co-localization of GH and PRL, both hormones were co-packaged in the same secretory granules within a single cell. Such cells were scarce, small, irregularly shaped, and observed only in pregnant rats. These mixed GH-PRL cells contained not only mixed GH-PRL granules but also granules containing only GH or PRL. This suggests that these bihormonal cells are able to synthesize, synchronously or asynchronously, GH and PRL. Furthermore, granule extrusion from the mixed cells was clearly shown in this study. It seems likely that the mixed GH-PRL cells reveal active cellular function in the pituitary gland of the pregnant rat.