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At least 1,099 records · Page 61Linked to original sources
PubMed1992

Role of dopamine in the regulation of proopiomelanocortin (POMC) mRNA levels in the arcuate nucleus and pituitary gland of the female rat as studied by in situ hybridization.

The effects of the dopaminergic antagonist haloperidol (HAL) as well as the D2 dopamine receptor agonist bromocriptine (BRO) on proopiomelanocortin (POMC) mRNA levels in the female rat arcuate nucleus and pituitary were investigated by quantitative in situ hybridization. Since we had already shown that sex steroids could induce a decrease in POMC mRNA levels in the arcuate nucleus of castrated rats, the involvement of the dopaminergic system in the inhibitory effect of estradiol (E2) was also investigated. In situ hybridization was performed on paraformaldehyde-fixed cryostat sections through the arcuate nucleus and whole pituitary gland using a 35S-labelled cDNA probe encoding for POMC. In the arcuate nucleus of intact animals, a 14-day treatment with BRO increased by 54% the number of silver grains/unit of surface of labelled neurons while HAL decreased by 30% the value of this parameter. Hypophysectomy which induced a 20% decrease in the hybridization signal could not prevent the effects of BRO or HAL. Ovariectomy performed 14 days earlier increased by 20% the number of silver grains while a 14-day treatment of ovariectomized animals with E2 decreased the hybridization signal by 32%. On the other hand, the concomitant administration of HAL and E2 did not induce significant variations in POMC mRNA levels compared to those obtained following HAL administration, but slightly decreased the hybridization signal by 20% compared to that induced by E2 alone. In the intermediate lobe of the pituitary, BRO markedly depressed (30% of control values) and HAL increased by 50% the levels of POMC mRNA. The present data clearly demonstrate that POMC mRNA levels are differently regulated by dopamine in the intermediate lobe of the pituitary and the arcuate nucleus and that the effects of BRO and HAL on arcuate POMC mRNA are not mediated by the pituitary gland. They do not allow to draw any definite conclusion about the possible involvement of the dopaminergic system in the inhibitory role of E2 on POMC gene regulation.

Animals↗
PubMed1991

Distribution of angiotensinogen immunoreactivity in rat anterior pituitary glands.

Angiotensin II (AII) has been previously shown to be localized in the gonadotropes of the rat anterior pituitary gland. Renin and angiotensin-converting enzyme, two enzymes that participate in the generation of AII, also have been shown to be present in gonadotropes. To determine whether angiotensinogen, the precursor to AII, is present in the same cells, we have stained rat anterior pituitary sections with an antirat angiotensinogen antiserum. Angiotensinogen staining was observed in cells that had a distinctive distribution at the periphery of the gland; the number of these cells and the intensity of the staining were increased in the pituitaries of rats that had been nephrectomized 24 hr before sacrifice. When double staining was performed, we never observed colocalization of angiotensinogen with any of the known pituitary hormones or with S100 protein. The results show that in the rat anterior pituitary gland, angiotensinogen is present, at least for the most part, in cells that are different from those containing renin, angiotensin-converting enzyme, and AII.

Angiotensin II↗
PubMed1987

Suckling influences the in vitro assembly of anterior pituitary gland tubulin into microtubules in the lactating rat.

Microtubules in the lactating rat anterior pituitary gland were depolymerized into their constituent tubulin monomers by homogenizing the pituitary tissue at 4 degrees C. The optimal conditions for the assembly of the pituitary tubulin into microtubules were established. It was found that the extent of assembly at 37 degrees C and pH 6.8 increased as a function of protein concentration, was dependent upon the GTP concentration present in the assembly buffer, and was inhibited by cold, Ca2+, and tubulin antibody. Next, this method was used to determine whether suckling affected the extent to which anterior pituitary tubulin of the rat assembled into microtubules. The tubulin fraction from rats which were suckled for 30 min assembled into microtubules to a lesser extent than did that from nonsuckled controls. These results suggest that the tubulin fraction obtained from the suckled rats is impaired in its ability to polymerize into microtubules.

Animals↗
PubMed1976

Functional differentiation of the FSH-synthesizing cells in the pars distalis of the fetal pituitary gland of the rat.

The onset of FSH synthesis in the embryonic pituitary gland of the rat was studied by a peroxidase-labelled antibody method. The first FSH-containing cells appeared on the 20th day of embryonic life. From that day onwards, FSH cells increased rapidly in number. It was found that in adult animals some pituitary cells reacted with both anti-HCG and anti-FSH sera, indicating the simultaneous presence of LH and FSH in the same cell.

Animals↗
PubMed1997

Endothelin receptors in rat pituitary gland.

1. We used the quantitative receptor autoradiographic method plus 125I-endothelin-1 (125I-ET-1), BQ-123, a specific antagonist for the endothelin ETA receptor, and sarafotoxin S6c, a selective agonist for the ETB receptor to investigate the ET receptor in the rat pituitary gland. 2. The method revealed that the BQ-123-sensitive ETA receptor was present predominantly in the anterior lobe and Rathke's pouch. 3. The posterior lobe contained BQ-123-sensitive ETA and sarafotoxin S6c-sensitive ETB receptors, in almost the same proportion. There was no significant 125I-ET-1 binding to the intermediate lobe. 4. Knowledge of the heterogeneous distribution of ET receptor subtypes in the pituitary gland supplies information that will be pertinent to physiological investigations of the gland.

Animals↗
PubMed1993

In vitro effect of ethanol on LH and FSH secretion by pituitary glands of female rats.

The effect of ethanol (EtOH) on LH and FSH release in vitro has been studied in order to determine whether the effect of alcohol observed in vivo could be mediated by a direct action at the level of the anterior pituitary. Pituitary glands were incubated for 4 hours in TC-199 medium with or with 100 mM ethanol. Basal gonadotrophin release was examined as well as secretion stimulated by luteinizing hormone releasing hormone (LHRH) in the presence or absence of cycloheximide. The total amount of LH and FSH released during the incubation period was calculated. Ethanol did not significantly alter basal gonadotrophin release or LHRH-stimulated FSH release. However, LH secretion induced by LHRH was decreased by EtOH when compared to the LHRH-stimulated group. Cycloheximide decreased the LHRH-stimulated release of LH and FSH but this effect was not altered by EtOH. The results show that EtOH alters the release but not the synthesis of gonadotrophins by a direct effect on the anterior pituitary gland.

Animals↗
PubMed1979

Biosynthesis and degradation of prolactin in the rat anterior pituitary gland. Time course of incorporation of label in vitro and evidence for rapid degradation.

Biosynthesis of prolactin was studied in anterior pituitary glands from female rats, incubated in vitro. In this system [3H]leucine was incorporated into pituitary proteins, including somatotropin (growth hormone) and prolactin. The rate of uptake of label into prolactin (and to a lesser extent into total protein) slowed considerably during the first 2 h of incubation, although the rate of uptake into somatotropin was constant for 8 h. The most probable explanation for this apparent decrease in the rate of prolactin synthesis is degradation of prolactin in the gland. Degradation of this hormone was also demonstrated by incubating prelabelled pituitaries in unlabelled medium and following the content of labelled prolactin, and by studying the hormonal content of pituitary glands (by radioimmunoassay) before and after incubation. Degradation of prolactin appears to be much more rapid than that of somatotropin, and may represent a physiological mechanism whereby over-accumulation of prolactin is prevented when secretion of the hormone has been rapidly switched off.

Animals↗
PubMed1983

The pituitary gland in untreated Addison's disease. A histologic and immunocytologic study of 18 adenohypophyses.

The pituitary glands of 18 patients with untreated Addison's disease were studied by histologic and immunocytochemical methods. Adrenal destruction was caused by tuberculosis (13 cases) or autoimmune adrenalitis (five cases), and the duration of the adrenal insufficiency ranged from one to 16 years. Both diffuse and nodular hyperplasia of corticotropic cells were evident in each case, and the extent of hyperplasia correlated with the duration of disease. In five cases, nodular proliferations with morphologic features between those of hyperplasia and those of adenoma, termed tumorlets, were identified, as were two microadenomas, only one of which was available for study. In all instances, the proliferating corticotrophs stained positively with PAS and were immunoreactive for adrenocorticotropic hormone and beta-endorphin. We conclude that diffuse and nodular corticotroph hyperplasia are common in untreated Addison's disease, although frank adenoma formation seems to be rare. The latter may be related to the short duration of disease or may imply the absence of additional, unknown factors that are required for adenoma growth.

Addison Disease↗
PubMed2000

Genetic regulation of the embryology of the pituitary gland and somatotrophs.

Extrinsic and intrinsic signaling gradients determine expression patterns of pituitary-specific factors in the developing anterior pituitary gland. The temporal and spatial relations of these developmental factors are required for the determination of each of the pituitary cell lineages. Rpx is required for early differentiation of the anterior pituitary. The determination of the somatotroph cell line is dependent on the transcription factors Lhx3, Prop-1, and Pit-1. Pit-1 also plays a role in the activation and regulation of the somatotroph gene product, GH. Additional factors such as CREB and the GHRH receptor, may be involved in somatotroph determination, while Zn-15 and Pitx2 may be involved in GH gene activation.

Animals↗
PubMed1984

Comparison of the effects of Althesin and sodium pentobarbitone on the regional uptake of 2-deoxyglucose by the brain and pituitary gland of the rat: selective effects on pars intermedia.

The uptake of radiolabelled 2-deoxyglucose (2DG) was used to compare the effects of the steroid anaesthetic, Althesin (alphaxalone plus alphadolone acetate) with those of sodium pentobarbitone on the regional metabolism of the brain and pituitary gland. Experiments were carried out on adult female Wistar rats. Studies on conscious animals were carried out with the aid of an indwelling intra-atrial catheter. The uptake of 2DG was measured both by liquid scintillation spectroscopy of 3H-2DG in tissue blocks and by quantitative autoradiography with 14C-2DG. Both anaesthetics significantly reduced uptake of 3H-2DG in the frontal, parietal and occipital cortex, and striatum and thalamus, but 3H-2DG uptake was significantly increased in the pituitary gland. Similar effects were found by measuring 14C-2DG uptake, and this technique showed further that Althesin, but not sodium pentobarbitone, selectively increased (2-fold) the uptake of 14C-2DG by the pars intermedia. The increase in 14C-2DG uptake by the pars intermedia in animals anaesthetized with Althesin was significantly reduced by a lesion placed in the arcuate nucleus. The most likely explanation for the effects of Althesin on the pars intermedia is that this anaesthetic increases the activity of arcuate neurons that innervate the pars intermedia.

Alfaxalone Alfadolone Mixture↗
PubMed1984

Demonstration of stellate cells of the pars intermedia of the pituitary gland using a new silver impregnation technique.

The pars intermedia of the pituitary gland in the rat and other species contains, in addition to secretory cells, stellate cells first characterized by using electron microscopy. The distribution and relationships of these cells is difficult to assess at the ultrastructural level. We have developed an ammoniacal silver nitrate method for stellate cells of the pars intermedia. Staining is carried out in 15 micron sections of buffered formalin fixed, paraffin embedded pituitaries. This method shows that in the rat pars intermedia, stellate cells showing numerous cytoplasmic projections are abundant in, and evenly distributed throughout, pars intermedia lobules.

Animals↗
PubMed2004

Role of PROP1 in pituitary gland growth.

Mutations in the PROP1 transcription factor gene lead to reduced production of thyrotropin, GH, prolactin, and gonadotropins as well as to pituitary hypoplasia in adult humans and mice. Some PROP1-deficient patients initially exhibit pituitary hyperplasia that resolves to hypoplasia. To understand this feature and to explore the mechanism whereby PROP1 regulates anterior pituitary gland growth, we carried out longitudinal studies in normal and Prop1-deficient dwarf mice from early embryogenesis through adulthood, examining the volume of Rathke's pouch and its derivatives, the position and number of dividing cells, the rate of apoptosis, and cell migration by pulse labeling. The results suggest that anterior pituitary progenitors normally leave the perilumenal region of Rathke's pouch and migrate to form the anterior lobe as they differentiate. Some of the cells that seed the anterior lobe during organogenesis have proliferative potential, supporting the expansion of the anterior lobe after birth. Prop1-deficient fetal pituitaries are dysmorphic because mutant cells are retained in the perilumenal area and fail to differentiate. After birth, mutant pituitaries exhibit enhanced apoptosis and reduced proliferation, apparently because the mutant anterior lobe is not seeded with progenitors. These studies suggest a mechanism for Prop1 action and an explanation for some of the clinical findings in human patients.

Animals↗
PubMed1980

Distribution of immunoreactive calcitonin in the rat pituitary gland.

Immunohistochemical (immunoperoxidase) studies were performed on 478 sections from 97 rat pituitary glands with rabbit antisera to unconjugated human synthetic calcitonin beta-endorphin, and/or ACTH-(17--39). Calcitonin-positive cells were present in a majority of the anterior lobes studied, whereas they were present in only a minority of the intermediate lobes. Calcitonin-positive cells were also present in chronically thyroidectomized animals. Beta-Endorphin-positive cells were uniformly present in the intermediate lobes as were the ACTH-positive cells. In the anterior pituitary lobes, beta-endorphin-positive cells were more populous than the ACTH-positive cells, and in general, there was a dissociation of the cellular elements containing beta-endorphin, ACTH, and calcitonin. Although it remains possible that there is calcitonin-like immunoreactivity within a precursor molecule that is differentially processed by pituitary cells, these studies are more consistent with the view that immunoreactive calcitonin is present in pituitary cells which are not as yet precisely and consistently related to any identifiable population of hormone-producing cells.

Animals↗