Distribution of immunoreactivities for adenohypophysial hormones in the pituitary gland of the polypteriform fish, Polypterus endlicheri

Polypteriform fish constitutes the most primitive living descendent of the ancient bony fish. In polypteriform fish, only proopiomelanocortin (POMC) has been identified so far in the adenohypophysis, which is surprising in view of their evolutionary importance. In the present study, distribution of immunoreactive adenohypophysial hormones was examined in juvenile individuals of Polypterus endlicheri. Antisera to tetrapod and fish adenohypophysial hormones were used as immunostaining probes. Adrenocorticotropin (ACTH)-like cells were detected by antisera to salmon POMC N-terminal peptide, porcine ACTH and mammalian alpha-melanotropin (MSH), and were distributed in the rostral pars distalis in close proximity to the hypophysial duct. MSH-like cells were found in the pars intermedia, and were stained by anti-salmon N-Ac-beta-endorphin II as well as anti-mammalian alpha-MSH and anti-salmon POMC-N terminal peptide. Prolactin (PRL)-like cells were detected only after application of anti-sturgeon PRL, and were distributed in the rostral pars distalis, where PRL-positive material was found in columnar mucinous cells lining the diverticuli of the hypophysial duct. Growth hormone (GH)-like cells were stained with antisera to sturgeon GH, human GH, salmon GH and blue shark GH, and were distributed in the proximal pars distalis. Somatolactin (SL)-like cells were stained with anti-salmon SL, and were distributed in the pars intermedia. Two types of glycoprotein hormone-positive cells were detected in the proximal pars distalis. Although both types of cells were stained with several antisera to glycoprotein hormones, such as sturgeon LHbeta and salmon LHbeta, it was difficult to know which types of cells produce LH, FSH, or TSH. Thus, the present study revealed seven types of adenohypophysial hormone-like cells in the Polypterus pituitary gland, which may provide the morphological basis for better understanding on evolution of the pituitary gland and the adenohypophysial hormones in vertebrates.     

Histopathology of the pituitary gland in neonatal little (lit) mutant mice.

The pituitary gland in the little (lit) mutant mouse was analyzed with respect to the cytoarchitecture of the pars distalis and the volumetric density of immunoreactive growth hormone (GH) cell granules in neonatal lit/lit and normal C57BL mice. At 8 days postnatally the volume of GH granules/total tissue was significantly less in the lit/lit pars distalis, and the cells were loosely arranged, as compared with the normal pars distalis. In newborn mice a statistically significant difference could not be detected between normal and lit/lit mice with respect to the volumetric density of GH granules; however, differences occurred in the cytoarchitectural organization of the pars distalis. These differences included prominent vascular channels and well-defined cords and clusters of cells in the normal newborn mice, in contrast to indistinct vascular elements and a more diffuse arrangement of cells in lit/lit.     

Somatostatin in the brain and the pituitary of some teleosts

Summary Immunocytochemical investigations show that somatostatin (SRIF)-like immunoreactive material is present in the brain and the pituitary of nine different species of teleosts. In the brain, immunoreactive perikarya and fibers are observed in the preoptic periventricular nucleus, the entopeduncular nucleus, the anterior periventricular nucleus, and the nucleus lateralis tuberis. In the pituitary, SRIF-like-immunoreactive fibers occur in the proximal pars distalis (PPD), which contains the growth hormone (GH)-secreting cells. Nerve fibers are scattered among GH cells (cyprinids), or end on the basal lamina at the neuroglandular interface of the PPD (eel, salmonids). In the eel, the proximal neurohypophysis does not penetrate deeply into the PPD that is very poorly vascularized. In some species, e.g. Myoxocephalus, SRIF-like immunoreactive fibers are also observed in the caudal neurohypophysis, and even among MSH cells of the pars intermedia.In long-term starved carps and eels, the amount of SRIF-like material in the pituitary is clearly reduced. A possible role of SRIF in the concomitant stimulation of GH cells is discussed.     

Identification by immunofluorescence of prolactin-and somatotropin-producing cells in the pituitary gland of the Mexican axolotl (Ambystoma mexicanum,Shaw)

Summary The indirect immunofluorescence procedure was used to identify prolactin (LTH)-and somatotropin (STH)-producing cells in the pituitary of the Mexican axolotl. Histological staining techniques were employed to corroborate immunocytological results. The LTH cells are large, orange-staining cells (acidophils 1) distributed in the posterior two-thirds of the pars distalis. The STH cells are small, erythrosinophilic elements (acidophils 2) principally concentrated in the dorsal part of the pars distalis.     

Immunocytochemical identification and ontogeny of adenohypophyseal cells in a cave fish,Phreatichthys andruzzii (Cypriniformes: Cyprinidae)

The morphogenesis of the pituitary gland and the chronological appearance of adenohypophyseal cells were investigated for the first time in the Somalian cave fish Phreatichthys andruzzii by immunocytochemistry. The adult adenohypophysis contained: a rostral pars distalis, with prolactin (PRL) cells arranged in follicles and adrenocorticotropic (ACTH) cells, a proximal pars distalis with somatotropic (GH), β‐thyrotropic (TSH), β‐gonadotropic type I (FSH) and type II (LH) cells and a pars intermedia with α‐somatolactin (SL), α‐melanotropic (MSH) and β‐endorphin (END) cells. All regions were deeply penetrated by neurohypophyseal branches. At hatching (24 h post‐fertilization) the pituitary was an oval cell mass, close to the ventral margin of diencephalon. The first immunoreactive cells appeared as follows: PRL at 0·5 days after hatching (dah), GH and SL at 1·5 dah, END at 2 dah, TSH, ACTH and MSH at 2·5 dah, FSH at 28 dah and LH at 90 dah. The neurohypophysis appeared at 5 dah and branched extensively inside the adenohypophysis at 130 dah, but there was no boundary between rostral pars distalis and proximal pars distalis at this stage. The potential indices of prolactin and growth hormone production increased until 28 and 60 dah, respectively. The potential index of growth hormone production correlated positively with total length. Activity of PRL and GH cells, measured as ratio of cell area to nucleus area, was significantly higher in juveniles than in larvae.     

Quantitative aspects of growth hormone cell maturation in the normal and little mutant mouse

Growth hormone (GH) cells were analyzed by means of ultrastructural morphometry in the pars distalis of pituitary glands from male adult and immature normal (C57BL) and homozygous little (lit/lit) mutant mice. Thin sections were exposed to anti-GH serum and processed immunocytochemically with the colloidal-gold technique. In the pars distalis of adult lit/lit mice, the mean volume density of GH cells/total tissue was 24% of the normal value, granules/GH cells was 58% of normal, and granules/total tissue was only 12% of normal. Deficits in all of these parameters likewise occurred in immature glands, though to a lesser extent than in the adults. The results indicate that the GH deficiency in this mutant reflects quantitative deficits in both the secretory granule content of GH cells, as well as the GH cell content of the gland, with the latter being the more severely affected.     

Differential distribution of orexin-A-like and orexin receptor 1 (OX1R)-like immunoreactivities in the Xenopus pituitary

Immunohistochemical techniques were employed to investigate orexin-A-like and orexin receptor 1 (OX1R)-like immunoreactivities in the Xenopus pituitary gland. Orexin-A-immunoreactive cells were mainly scattered in the posterior half of the pars distalis. They corresponded to thyroid-stimulating hormone (TSH)-containing cells and so far have not corresponded to other types of pituitary adenocytes. On the other hand, OX1R-immunoreactive cells were mainly distributed in the anterior half of the pars distalis and corresponded to prolactin (PRL)-containing cells; however, we found that OX1R-immunoreactive cells did not correspond to other types of adenocytes in the Xenopus pituitary. These results suggest that an orexin-A-like substance secretes with and/or without TSH from TSH-containing cells and that the peptide modulates the functions of PRL-containing cells via OX1R in a paracrine fashion.     

Adenohypophysial cell types in the lamprey pituitary: current state of the art

Adenohypophysial cell types in the pituitary of adult sea lampreys, Petromyzon marinus, was localized by means of immunocytochemical and lectin cytochemical techniques. At least four types of adenohypophysial hormone cells are present in the pituitary of adult sea lampreys. The first type of cell is ACTH-like and occupies most parts of the rostral pars distalis (RPD), but a few scattered ACTH-like cells are also present in the proximal pars distalis (PPD). The second type of cell is MSH-like and occupies the whole pars intermedia. The third type of cell is GH/PRL-like and occupies the dorsal half of the PPD. These GH/PRL-like cells were initially detected by heterologous immunocytochemistry using antibodies to salmon GH, salmon PRL and blue shark GH, after hydrated autoclave pretreatment of sections. Later, by use of an antiserum raised against a synthetic peptide corresponding to the partial sequence of lamprey GH/PRL, the same cells as those containing GH/PRL-like immunoreactivity were stained positively. Similarity of the topographic distributions between lamprey GH/PRL-like cells and gnathostome fish GH cells in the pituitary suggests that GH/PRL-like cells in the lamprey may be GH cells. The last type of cell is GTH-like and occupies the ventral half of the PPD. Although GTH has not yet been isolated from the lamprey pituitary, our immunocytochemical data suggest that GTH-like material in the sea lamprey pituitary is more closely related to mammalian-like LH, rather than to FSH or TSH. These four types of adenohypophysial cells occupy most parts of the lamprey adenohypophysis and indeed there is little room for TSH or PRL cells. Thus, the present study further suggests that GH and LH-like GTH are ancestral forms of GH/PRL/SL family and glycoprotein hormones, respectively.     

Immunohistochemical identification of cells in the pars distalis of the pituitary of the lizard Anolis carolinensis

Immunocharacteristics of the pars distalis cells of the pituitary of the male lizard A. carolinensis are determined by employing the immunoperoxidase technique with antisera to mammalian pituitary hormones. On the basis of their immunoreactivity, 5 different cell types with characteristic anatomical distribution are recognized. ACTH cells are found in the rostral half of the pars distalis, and PRL cells in the rostral two thirds of the pars distalis. GH and TSH cells are located in the caudal half of the pars distalis. GTH cells are distributed throughout the gland. When consecutive sections are stained with antiserum to ovine FSH or its beta-subunit and to ovine LH, the same cells show immunoreactivity to all the three antisera. None of the GTH cells show positive immunoreactivity to ovine beta-LH antiserum. The results suggest the existence of one gonadotropic cell type in the pituitary of this lizard.     

Peptides with NH2-terminal tryptophan in adrenocorticotrophic hormone and melanocyte-stimulating hormone granules of adenohypophysis.

Fluorescence microscopy has demonstrated formaldehyde-ozone-induced fluorescence in the pars intermedia cells (melanocyte-stimulating hormone cells) and in certain cells of the pars distalis of the mammalian pituitary. From histochemical and chemical evidence the fluorescence is believed to reflect the presence of peptides with NH2-terminal tryptophan. In the pars distalis of hamster, cat and pig pituitary, the cells that exhibit formaldehyde-ozone-induced fluorescence have now been identified as adrenocorticotrophic hormone (ACTH) cells by immunohistochemistry. Granules from pig pituitaries were purified by passage through a succession of Millipore filters followed by centrifugation on a continuous sucrose gradient. Two granular fractions were identified by electron microscopy and found to contain high concentrations of peptides with NH2-terminal tryptophan as well as high ACTH bioactivity. These fractions, when pelleted and analyzed histochemically, displayed formaldehyde-ozone-induced fluorescence and ACTH-like immunoreactivity.     

Distribution of 7B2 (secretogranin V)-like immunoreactivity in the Japanese red-bellied newt (Cynops pyrrhogaster) pituitary

In this study, we examined 7B2 (secretogranin V)-like immunoreactivity (IR) in the Japanese red-bellied newt (Cynops pyrrhogaster) pituitary. Results showed that the pars nervosa was filled with immunoreactive granules. In the pars intermedia, all melanotrophs showed 7B2-IR. In the pars distalis, immunoreactive cells were dispersed, and the 7B2-immunoreactive cells were also immunopositive for the β-subunit of bullfrog luteinizing hormone (fLHβ). 7B2-IR co-localized with fLHβ-IR in the same secretory granules. Our results suggest that 7B2 may participate in the secretion processes of gonadotropins in the pars distalis.     

Tilapia adropin: the localization and regulation of growth hormone gene expression in pituitary cells

The peptide hormone adropin, encoded by the energy homeostasis-associated (Enho) gene, plays a role in energy homeostasis and the control of vascular function. The aim of this study was to examine the role of adropin in growth hormone (GH) gene expression at the pituitary level in tilapia. As a first step, the antiserum for the tilapia adropin was produced, and its specificity was confirmed by antiserum preabsorption and immunohistochemical staining in the tilapia pituitary. Adropin could be detected immunocytochemically in the proximal pars distalis (PPD) of the tilapia pituitary. In primary cultures of tilapia pituitary cells, tilapia adropin was effective in increasing GH mRNA levels. However, removal of endogenous adropin by immunoneutralization using adropin antiserum inhibited GH gene expression. In parallel experiments, pituitary cells co-treated with ovine pituitary adenylate cyclase activating polypeptide 38 (oPACAP38) and adropin showed a similar increase level compared to those treated with oPACAP38 alone, whereas insulin-like growth factor 1 (IGF1) not only had an inhibitory effect on basal GH mRNA levels, but also could abolish adropin stimulation of GH gene expression. In pituitary cells pretreated with actinomycin D, the half-life of GH mRNA was enhanced by adropin. Taken together, these findings suggest that adropin may serve as a novel local stimulator for GH gene expression in tilapia pituitary.     

乌龟脑垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞:即生长激素(GH)分泌细胞、催乳激素(PRL)分泌细胞、促甲状腺激素(TSH)分泌细胞、促肾上腺皮质激素(ACTH)分泌细胞、促性腺激素(GTH)分泌细胞和非分泌类型滤泡-星形细胞(FS)。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。       

乌脑龟垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞：即生长激素（GH）分泌细胞、催乳激素（PRL）分泌细胞、促甲状腺激素（TSH）分泌细胞、促肾上腺皮质激素（ACTH）分泌细胞、促性腺激素（GTH）分泌细胞和非分泌类型滤泡．星形细胞（Fs）。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。     

Leucine-enkephalin-like immunoreactivity is localized in luteinizing hormone-producing cells in the axolotl (Ambystoma mexicanum) pituitary

In this study, we used immunohistochemical techniques to determine the cell type of leucine-enkephalin (Leu-ENK)-immunoreactive cells in the axolotl (Ambystoma mexicanum) pituitary. Immunoreactive cells were scattered throughout the pars distalis except for the dorso-caudal portion. These cells were immuno-positive for luteinizing hormone (LH), but they were immuno-negative for adrenocorticotrophic, growth, and thyroid-stimulating hormones, as well as prolactin. Immunoelectron microscopy demonstrated that Leu-ENK-like substance and LH co-localized within the same secretory granules. Leu-ENK secreted from gonadotrophs may participate in LH secretion in an autocrine fashion, and/or may participate in the release of sex steroids together with LH.     

Ultrastructural identification of catecholaminergic fibers in the goldfish pituitary

Summary The monoaminergic innervation of the goldfish pituitary gland was studied by means of light- and electronmicroscopic radioautography after in vitro administration of ³H-dopamine. The tracer was specifically incorporated and retained by part of the type-B fibers innervating the different lobes of the pituitary. In the rostral pars distalis labeled fibers were most frequently observed in contact with the basement membrane separating the neurohypophysis and the adenohypophysis. In the proximal pars distalis and the pars intermedia, labeled profiles were detected in the neural tissue and in direct contact with the different types of secretory cells.According to the previous data concerning the uptake and retention of tritiated catecholamines in the central nervous system, it is assumed that the labeled fibers are mainly catecholaminergic (principally dopaminergic). This study provides morphological evidence for a neuroendocrine function of catecholamines in the goldfish.     

Uptake and retention of sex steroids by the baboon pituitary gland--evidence of sexual dimorphism with respect to dihydrotestosterone

The localization and identification of the target cells for estradiol (E2) and dihydrotestosterone (DHT) were studied in the pituitary gland of male and female baboons (Papio cynocephalus) using autoradiography and autoradiography combined with immunocytochemistry. The largest number of cells which sequestered 3H-E2 were located in the pars distalis of both the males and females. Immunocytochemistry revealed that these target cells were predominantly gonadotrophs and mammotrophs, albeit a few somatotrophs and thyrotrophs were also labeled. A distinct sexual dimorphism was not observed with respect to the uptake and retention of the tritiated estrogen but was clearly evident in those animals given 3H-DHT. Significantly more cells in all three lobes of the male baboon, the partes distalis, intermedia and nervosa, concentrated the radiolabeled androgen as compared to that found in the females. Regardless of sex, however, the gonadotrophs were the major cell type in the pars distalis which was labeled. A small population of mammotrophs, somatotrophs and thyrotrophs also retained 3H-DHT. In both males and females, the pars nervosa was the portion of the hypophysis most sensitive to 3H-DHT. These findings indicate that all three lobes of the hypophysis of the male and female baboon contain target cells for E2 and DHT and that the propensity for DHT uptake is greater in males than in females.     

Immunohistochemical Identification of the Adenohypophysial Cells in the Indian Paddy Field Frog,Rana limnocharis

Cells of the pituitary pars distalis (PD) and pars intermedia (PI) in the frog Rana limnocharis have been identified by an unlabelled antibody enzyme method using antisera developed in rabbit against mammalian hypophysial hormones. On the basis of their immunoreactivity, six types of cells, viz. thyrotropic (TSH), gonadotropic (GTH), prolactin (PRL), growth hormone (GH), corticotropic (ACTH) and melanotropic (MSH), cells have been recognized. GTH and PRL cells are distributed throughout the PD. GH cells usually occur in the anterodorsal and central region of the gland. Immunoreactive TSH cells are fewer in number and are localized in the ventromedian region of the PD. Cells showing immunoreactivity to ACTH 1–24 antiserum are encountered in the rostroventral part of the PD. Cells of the PI also show immunoreactivity to ACTH 1–24 antiserum. PI cells cross-react with α-MSH antiserum at all dilutions up to 1: 50 000. However, when the same antiserum was used at dilutions up to 1: 20 000, the ACTH cells of the PD also showed cross-reactivity.     

A systematic immunohistochemical survey of the distribution patterns of GH, prolactin, somatolactin, β–TSH, β–FSH, β–LH, ACTH, and α–MSH in the adenohypophysis of Oreochromis niloticus, the Nile tilapia

Fish pituitary plays a central role in the control of growth, development, reproduction and adaptation to the environment. Several types of hormone-secreting adenohypophyseal cells have been characterised and localised in diverse teleost species. The results suggest a similar distribution pattern among the species investigated. However, most studies deal with a single hormone or hormone family. Thus, we studied adjacent sections of the pituitary of Oreochromis niloticus, the tilapia, by conventional staining and immunohistochemistry with specific antisera directed against growth hormone (GH), prolactin (PRL), somatolactin (SL), thyrotropin (beta-TSH), follicle-stimulating hormone (beta-FSH), luteinising hormone (beta-LH), adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (alpha-MSH). The pituitary was characterised by a close interdigitating neighbourhood of neurohypophysis (PN) and adenohypophysis. PRL-immunoreactive and ACTH-immunoreactive cells were detected in the rostral pars distalis. GH-immunoreactive cells were present in the proximal pars distalis (PPD). A small region of the PPD contained beta-TSH-immunoreactive cells, and beta-LH-immunoreactive cells covered approximately the remaining parts. Centrally, beta-FSH-immunoreactive cells were detected in the vicinity of the GH-containing cells. Some of these cells also displayed beta-LH immunoreactivity. The pars intermedia was characterised by branches of the PN surrounded by SL-containing and alpha-MSH-immunoreactive cells. The ACTH and alpha-MSH antisera were observed to cross-react with the respective antigens. This cross-reactivity was abolished by pre-absorption. We present a complete map of the distinct localisation sites for the classical pituitary hormones, thereby providing a solid basis for future research on teleost pituitary.