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PubMed1992

Molecular characterization of D2 dopamine-like receptors from brain and from the pituitary gland.

D2 dopamine-like receptors have been purified from five bovine brain regions (caudate nucleus, putamen, olfactory tubercle, frontal cortex, cerebellum) and the anterior and neurointermediate lobes of the pituitary gland using a combined ligand-affinity and lectin-affinity chromatography procedure. In all the brain regions except cerebellum and in the neurointermediate lobe of the pituitary gland the purified species appeared as a M(r) 95,000 doublet on SDS-PAGE. In the anterior lobe of the pituitary an additional M(r) 142,000-145,000 species was seen. The M(r) 95,000 species had a low affinity for the lectin wheat germ agglutinin (WGA) whereas the M(r) 142,000-145,000 species had a higher affinity for WGA and additionally showed some affinity for concanavalin A. It is concluded that both the M(r) 95,000 and 142,000-145,000 species are D2 dopamine-like receptors and that the differences between the species are mainly at the oligosaccharide level. Some evidence was also obtained for heterogeneity at the protein level which may correspond to the D2(short) and D2(long) isoforms of these receptors.

Animals↗
PubMed2003

Binding site of salsolinol: its properties in different regions of the brain and the pituitary gland of the rat.

It has been recently shown that salsolinol (SAL) is present in the hypothalamic neuroendocrine dopaminergic (NEDA) system and appears to be a selective and potent stimulator of prolactin (PRL) secretion in the rat. Furthermore, the lack of interference of SAL with 3H-spiperone binding in the striatum and the anterior lobe (AL) of the pituitary gland has been also demonstrated. These data clearly indicate that SAL does not act at the dopamine (DA) D(2) receptors, and suggest that SAL supposedly has a binding site through which the secretion of PRL may be affected. Therefore, binding of 3H-SAL to different regions of the central nervous system (CNS) has been investigated. Specific and saturable binding has been detected in the striatum, cortex, median eminence and in the hypothalamus as well as in the AL and the neuro-intermediate lobe (NIL) of the pituitary gland. K(D) values of the bindings were in the nanomolar range in all tissue tested. 3H-SAL displacing activity of several agonists and antagonists of known DA receptors have also been tested. It has been found that DA and in a lesser extent, apomorphine could displace 3H-SAL, but other DA receptor specific ligands have not been able to affect it. Furthermore, several pharmacologically active compounds, selected on the basis of their influence on DA synthesis, transport mechanisms and signal transduction, have also been tested. Neither mazindol (a selective DA transporter inhibitor) nor clonidine (an alpha(2)-adrenoreceptor agonist) could alter SAL binding. At the same time, L-dopa, carbidopa, benserazide and alpha-methyldopa were able to displace 3H-SAL. The possible changes in SAL binding due to physiological and pharmacological stimuli, like suckling stimulus and reserpine pretreatment (that blocks vesicular monoamine transport in DA terminals), respectively, have also been investigated. In the NIL of the pituitary gland and in the median eminence of the hypothalamus the binding decreased following 10 min of suckling stimulus compared to the binding detected in the same tissues obtained from mothers separated from their pups for 4h and not allowed to be suckled. At the same time, there were no changes in the binding at the AL and striatum. Following reserpine pretreatment that has completely prevented PRL releasing effect of SAL, the binding was significantly augmented. These results support our assumption that SAL should have specific binding sites through which it can affect PRL secretion. Furthermore, it clearly suggests that it may regulate DAergic neurotransmission of NEDA neurons by an altered intracellular or intraterminal synthesis and/or distribution of hypophysiotropic DA.

Animals↗
PubMed1975

Influence of the pituitary gland on insulin secretion in the genetically obese (ob/ob) mouse.

The influence of the pituitary gland of lean and genetically obese (ob/ob) mice on insulin secretion from microdissected pancreatic islets of lean and ob/ob mice has been studied by perifusing the pituitaries of these animals in series with the isolated islets and measuring insulin secretion at 5-min intervals over a period of 60 min. It has been shown that the pituitary perifusate of both lean and obese mice stimulate insulin secretion from lean mouse islets but not from obese mouse islets. The maximum stimulation occurs in the first 10 min and with the lean mouse pituitaries returns to the basal level in about 20 min, whereas with the obese mouse pituitaries insulin secretion is about double that from the control islets even after 40 min. A concentration of pure porcine ACTH equivalent to about three times the amount released from the pituitary gland under the experimental conditions used, caused only a small stimulation of insulin release. Possible interpretations of these findings and further lines of investigation are discussed.

Adrenocorticotropic Hormone↗
PubMed1997

High levels of human chymase expression in the pineal and pituitary glands.

The brain renin-angiotensin system plays a role in both cardiovascular homeostasis and neurosecretory functions. Since the mechanisms of angiotensin (Ang) II formation in the human brain have not been clarified, the aims of the present study were to determine the presence of human chymase and angiotensin I-converting enzyme (ACE) in human and non-human brains. In the human brain, the total Ang II-forming activity was significantly higher in the pineal and pituitary glands than those in other regions. In other species (rat, bovine and porcine), the level of chymase as well as total Ang II-forming activities in pineal glands were significantly lower than those in human glands. High levels of chymase-like immunoreactivity (ir) were found in the arteriolar endothelial cells, adventitial mesenchymal cells and in parenchymal cells of the human pineal and pituitary glands while ACE-ir was mostly observed in the endothelial cells and occasionally found in parenchymal cells. Our study provides the first evidence that human chymase exists in the pineal and pituitary glands. The remarkable regional and species differences in mechanisms of Ang II formation suggest a specific role of chymase or ACE in the human brain.

Adult↗
PubMed2003

Localization of the neuronal form of nitric oxide synthase (bNOS) in the diencephalon and pituitary gland of the catfish, Synodontis multipunctatus: an immunocytochemical study.

The distribution of the neuronal form of nitric oxide synthase (bNOS) was investigated in the brain and pituitary gland of the catfish, Synodontis multipunctatus. Immunoreactive neurons were found mainly in the nucleus praeopticus periventricularis, the parvocellular and supraoptic subdivisions of the nucleus praeopticus, the nucleus recessus lateralis and the nucleus recessus posterioris. In addition, some scattered bNOS labeled somata were noted in the dorsal hypothalamic area. A few positive cells in the adenohypophysis and some reactive fibers in the pituitary stalk were also seen. Our results are compatible with the notion that the cells expressing bNOS in the diencephalon and hypophysis are involved in the control of hormone regulation. Moreover, the presence of bNOS positive cells in the rostral pars distalis of the pituitary gland supports a role of nitric oxide in osmoregulation.

Animals↗
PubMed1989

Diurnal variation in the concentrations of catecholamines and indoleamines in the median eminence and in the intermediate and posterior lobes of the pituitary gland of the male rat.

Diurnal changes in monoamine concentrations were studied in the median eminence and in the intermediate and posterior lobes of the pituitary gland of the male rat. The concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline (NA) and dopamine (DA) were analyzed at 7 time points over a 24-h period. Diurnal variation was analyzed by analysis of variance (ANOVA) with time of day as a class variable as well as by 24 h and 12 h cosine curve fittings. There were marked time-dependent changes in the median eminence concentrations of 5-HT (ANOVA: P = 0.0085), 5-HIAA (P = 0.003) and NA (P = 0.0003). Cosine curves with 24-h periods fit the data points with peaks around 13.00 h. DA levels also varied with an apparent 24-h rhythm in the median eminence, but the changes did not reach the level of significance in the ANOVA. In the intermediate lobe of the pituitary gland, the concentrations of DA varied significantly during the course of the 24-h cycle (P = 0.0011) and were well-fitted to a 24-h cosine wave. The 5-HIAA levels also showed marked diurnal changes (P = 0.025) with an evident 12-h rhythm. In contrast, NA and 5-HT concentrations did not appear to vary during the 24-h cycle. In the posterior lobe of the pituitary gland. DA had a 24-h rhythm (P = 0.0005) similar to the intermediate lobe. NA and indoleamine levels did not show any significant variation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Blood flow and autoregulation in rat pituitary gland.

The authors describe an experimental model that allows dynamic studies of blood flow in the pituitary gland. Twenty-eight male Wistar rats were anesthetized and the pituitary gland was exposed using a parapharyngeal approach. Teflon-coated platinum wire electrodes were placed in the adenohypophysis near the midline and laterally as well as in the parietal cortex and the white matter. Blood flows were measured by the hydrogen clearance method. Baseline values were as follows: 89.9 +/- 22 ml/100 gm/min in the medial adenohypophysis, 55.9 +/- 8 ml/100 gm/min in the lateral adenohypophysis, 59.2 +/- 14 ml/100 gm/min in the parietal cortex, and 28.1 +/- 8.9 ml/100 gm/min in the white matter. Effective autoregulation was demonstrated by altering the blood pressure with metaraminol infusion or blood withdrawal. The range of autoregulation was wider in the adenohypophysis than in the cerebral cortex.

Animals↗
PubMed1976

Isolation of a new lipolytic-melanotropic peptide from human pituitary glands.

A new peptide having both lipolytic and melanotropic properties has been isolated from human pituitary glands. It has a molecular weight around 11,000, an amino acid composition different from the known lipolytic-melanotropic hormones, and an isoelectric point of 8.5. Although it is not entirely pure, there is no doubt that it differs from other known lipolytic-melanotropic substances in its total lack of methionine and tryptophan and its unusually high content of lysine and histidine. It has a melanocyte-stimulating hormone activity of 19 units/mug. As a lipolytic agent it is active with rabbit adipocytes, only slightly active with human cells and inactive with adipocytes from the rat.

Alanine↗
PubMed2003

IGF-I regulates pro-opiomelanocortin and GH gene expression in the mouse pituitary gland.

IGF-I is expressed in somatotrophs, and IGF-I receptors are expressed in most somatotrophs and some corticotrophs in the mouse pituitary gland. Our recent study demonstrated that IGF-I stimulates the proliferation of corticotrophs in the mouse pituitary. These results suggested that somatotrophs regulate corticotrophic functions as well as somatotrophic functions by the mediation of IGF-I molecules. The present study aimed to clarify factors regulating pituitary IGF-I expression and also the roles exerted by IGF-I within the mouse anterior pituitary gland. Mouse anterior pituitary cells were isolated and cultured under serum-free conditions. GH (0.5 or 1 microg/ml), ACTH (10(-8) or 10(-7) M), GH-releasing hormone (GHRH; 10(-8) or 10(-7) M), dexamethasone (DEX; 10(-8) or 10(-7) M) and estradiol-17beta (e2; 10(-11) or 10(-9) M) were given for 24 h. IGF-I mRNA levels were measured using competitive RT-PCR, and GH and pro-opiomelanocortin (POMC) mRNA levels were measured using Northern blotting analysis. GH treatment significantly increased IGF-I mRNA levels (1.5- or 2.1-fold). ACTH treatment did not alter GH and IGF-I mRNA levels. IGF-I treatment decreased GH mRNA levels (0.7- or 0.5-fold), but increased POMC mRNA levels (1.8-fold). GH treatment (4 or 8 microg/ml) for 4 days increased POMC mRNA levels. GHRH treatment increased GH mRNA levels (1.3-fold), but not IGF-I mRNA levels. DEX treatment significantly decreased IGF-I mRNA levels (0.8-fold). e2 treatment did not affect IGF-I mRNA levels. GH receptor mRNA, probably with GH-binding protein mRNA, was detected in somatotrophs, and some mammotrophs and gonadotrophs by in situ hybridization using GH receptor cDNA as a probe. These results suggested that IGF-I expression in somatotrophs is regulated by pituitary GH, and that IGF-I suppresses GH expression and stimulates POMC expression at the transcription level. Pituitary IGF-I produced in somatotrophs is probably involved in the regulation of somatotroph and corticotroph functions.

Adrenocorticotropic Hormone↗
PubMed1999

Estrogen action in the regulation of cell proliferation, cell survival, and tumorigenesis in the rat anterior pituitary gland.

Estrogens act as important regulators of cell proliferation, cell survival, and differentiation in a variety of organ systems and tissues and have been implicated in the etiology of a variety of malignant cancers and benign tumors. The anterior pituitary gland of the rat provides an excellent model for the study of estrogen action in the regulation of cell proliferation and survival. Estrogens stimulate proliferation of the prolactin (PRL)-producing lactotroph and enhance lactotroph survival. Through these actions on lactotroph proliferation and survival, estrogens induce or contribute to the development of PRL-producing pituitary tumors in several rat strains. Data from our laboratory and others indicate that estrogen-induced pituitary growth is rat strain specific and segregates as a quantitative genetic trait in crosses between different rat strains. The purpose of this review is to summarize current knowledge pertaining to estrogen action in the regulation of cell proliferation, cell survival, and tumorigenesis in the anterior pituitary gland of the rat species, Rattus norvegicus, and to illustrate the advantages of the rat pituitary gland as a model for elucidating the mechanisms through which estrogens regulate these processes.

Animals↗
PubMed1998

Characterization of the dopaminergic input to the pituitary gland throughout the estrous cycle of the rat.

Changes in the concentrations of dopamine (DA) and its major metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were characterized in the pituitary gland throughout the 4-day estrous cycle of the rat. Female rats were sacrificed at 2- to 3-hour intervals throughout each day of the 4-day estrous cycle. Pituitary glands were removed, and the concentrations of DA and DOPAC were determined by high-performance liquid chromatography coupled to electrochemical detection. The concentration of prolactin (PRL) in serum from these same animals was determined by radioimmunoassay. The concentration of DA in the anterior lobe was constant throughout most of the 4-day estrous cycle. Prior to initiation of the proestrous surge of PRL, there were significant (p < 0.05) decreases in the concentrations of both DA and DOPAC in the anterior lobe which returned to elevated baseline levels just prior to the termination of the proestrous surge of PRL. The concentrations of DA and DOPAC in the intermediate lobe exhibited a daily rhythm. However, in the intermediate as well as in the anterior lobe, there were significant (p < 0.001) decreases in the concentrations of both DA and DOPAC, coincident with the initiation of the proestrous surge of PRL. Similarly, coincident with the peak of the proestrous surge of PRL, there were significant (p < 0.001) increases in the concentrations of DA and DOPAC in the intermediate lobe, followed by a return to basal levels and resumption of the daily rhythm. The pattern of the concentrations of DA and DOPAC in the neural lobe was also daily in nature, with peaks occurring between 13.00 and 15.00 h each day of the 4-day estrous cycle. These data, taken together: (1) confirm that a decrease of the concentrations of DA and DOPAC occurs in the anterior lobe prior to the proestrous surge of PRL; (2) reveal that DA is released in a daily pattern at intermediate and neural lobes, and (3) suggest an apparent role for DA released to the intermediate lobe in the regulation of the proestrous surge of PRL.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2003

Characterization of tachykinin NK2 receptor in the anterior pituitary gland.

Tachykinins are a family of bioactive peptides that interact with three subtypes of receptors: NK1, NK2 and NK3. Substance P has greater affinity for NK1, and neurokinin A (NKA) for NK2 receptor subtype. Although only NK1 receptor has been characterized in the anterior pituitary gland, some evidence suggests the existence of NK2 receptors in this gland. Therefore, we investigated the presence of NK2 receptors in the anterior pituitary gland of male rats by radioligand binding studies using labeled SR48968, a non peptidic specific antagonist. [3H]SR48968 specific binding to cultured anterior pituitary cells was time-dependent and saturable, but with a lower affinity than previously reported values for cells expressing NK2 receptors. Unlabeled NKA inhibited only partially [(3)H]SR48968 specific binding to whole anterior pituitary cells. Since SR48968 is a non polar molecule, we performed experiments to discriminate surface from intracellular binding sites. SR48968 exhibited both surface and intracellular specific binding. Analysis of the surface-bound ligand indicated that [3H]SR48968 binds to one class of receptor with high affinity. Neurokinin A completely displaced [3H]SR48968 surface specific binding fitting to a two-site/two-state model with high and low affinity. Additionally, immunocytochemical studies showed that the NK2 receptor is expressed at least in a subset of lactotropes. These results demonstrate the presence of NK2 receptors in the anterior pituitary gland and suggest that NKA actions in this gland are mediated, at least in part, by the NK2 receptor subtype.

Animals↗
PubMed2006

Extracellular accumulations in the avian pituitary gland: histochemical analysis in two species of Indian wild birds.

Extracellular accumulations of two distinct types, colloid-filled follicles and fibrous-material-containing cysts, were observed in the pituitary gland of two species of Indian wild birds, Halcyon smyrnensis perpulchra and Lonchura striata striata. Colloid follicles were regular structures and distributed throughout the pars distalis (PD). The fibrous cysts were irregular structures, bigger than the colloid follicles and mostly observed towards the ventral margin of the PD. Sometimes disruption of the outer margin with depletion of fibrous material from the cavity was observed. Hormone-secreting cells of various types, anti-adrenocorticotropic-hormone-, anti-prolactin-, anti-growth-hormone- and anti-luteinizing-hormone-immunoreactive cells were encountered bordering both the colloid follicles and fibrous cysts. Neither the colloid nor the fibrous material showed any immunoreaction to any of the pituitary hormone antisera. On histochemical staining colloid was positive to periodic acid-Schiff (PAS) and fibrous materials stained with Alcian blue-PAS-orange G staining. Colloid depositions in the pituitary gland of these two wild birds were correlated to age, more in numbers in the adult birds than in the young ones. Fibrous-material-containing cysts were elucidated in the pituitary gland of adult birds only. These were more prevalent in the pituitary of reproductively active birds. Regular morphology of the colloid follicles, overall distribution in the adenohypophysis and dense nature of deposition of the colloid suggest the accumulation of this type may be the secretory products of both granulated and agranulated pituitary cell types. Absence of immunoreactivity of the colloid against pituitary hormone antisera points out that the storage form may differ chemically from the bioactive hormones. The spatial distribution of fibrous-material-containing cysts mostly towards the ventral PD, observations of immunoreactive cell fragmentations inside the cysts, and their disrupted margins suggest these structures may have some role in discharging the intraglandular degradation products.

Adrenocorticotropic Hormone↗
PubMed1991

Hypo- and hypercalcemic peptides in fish pituitary glands.

Immunoreactive parathyroid hormone (irPTH), PTH-related peptide (PTHrp), and stanniocalcin-like peptides were detected in Coho salmon pituitary glands. The PTH, PTHrp, and stanniocalcin immunoreactivity of the salmon pituitary was separated by high-performance liquid chromatography purification into distinct peptide fractions that coeluted with pure preparations of these hormones. Stanniocalcin was localized by immunocytochemistry in the neurohypophysis and preoptic area of the platyfish brain, in areas in which irPTH has previously been detected in other teleosts. Although it is well established that the fish pituitary exerts hypercalcemic control over calcium metabolism, these results demonstrate the presence of hyper- and hypocalcemic peptides in teleost pituitary glands. The detection of PTHrp in the fish pituitary is the first report of its presence outside of mammalian species and suggests an early evolutionary divergence of PTH and PTHrp from an ancestral gene.

Animals↗
PubMed1992

Metastatic renal cell carcinoma to the pituitary gland presenting with hypopituitarism.

A 57-year-old man with pituitary metastasis from renal cell carcinoma is reported. He underwent right nephrectomy and total pancreatectomy for renal cell carcinoma and its pancreatic metastasis, respectively. Imaging studies showed an intrasellar mass lesion. The examination revealed panhypopituitarism, diabetes insipidus and bitemporal hemianospia. Metastatic renal cell carcinoma was diagnosed by the biopsy of the pituitary tumor. Metastatic renal cell carcinoma to the pituitary gland, which is extremely rare, appears to have unique features of presenting with hypopituitarism and visual disturbance more frequently than other metastatic pituitary tumors.

Antineoplastic Combined Chemotherapy Protocols↗