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At least 487 records · Page 27Linked to original sources
PubMed1986

Influence of yohimbine on release of anterior pituitary hormones.

We used a double-blind crossover design to study the effects of alpha 2 adrenoreceptor blockade with yohimbine on levels of anterior pituitary hormones. A dose of yohimbine was used which raised plasma norepinephrine from 379 +/- 74 (S.E.) to 730 +/- 143 pg/ml and mean arterial pressure from 83 +/- 4 to 92 +/- 5 torr (p less than 0.025). This dose (125 micrograms/kg, then 1 microgram/kg/min) also altered mood when compared to saline infusion. In spite of these changes, when prolactin, cortisol, ACTH, beta-endorphin, TSH and growth hormone were measured after 45 minutes of yohimbine infusion, no changes from baseline were noted. These data suggest that in normal man, at rest, alpha 2 adrenoreceptors in the hypothalamus, adenohypophysis or other brain areas do not tonically modulate release of these hormones into the blood.

Adrenocorticotropic Hormone↗
PubMed1997

Pituitary hormones and immune function.

The pituitary gland plays a key role in the regulation of growth, differentiation and function of all cells in the body, including immunocytes. Immune reactions are generated through the proliferation of antigen-specific lymphocyte clones. Growth hormone and prolactin are required for the development of mature lymphocytes and for the maintenance of immunocompetence. These hormones enable lymphocytes to respond to antigen, which is delivered as an adherence signal in the context of major histocompatibility surface molecules of antigen-presenting cells. Numerous other adhesion molecules play a role in the regulation of lymphocyte activation. The activation process is completed by cytokine signalling, after which lymphocyte proliferation, differentiation and functional maturation take place. Interleukins, hormones and growth factors may all function as cytokines. Many lymphocytes exist in the body in a quiescent state, with minimal metabolic activities. These cells are maintained by competence hormones and insulin-like growth factor 1, which are present in the systemic and local environment. Apparently, some steroid hormones, opioid peptides and catecholamines are capable of modulating delivery of the signal from the lymphocyte membrane receptor to the nucleus. Steroid and thyroid hormones control nuclear transcription factors as their receptors, and thus are powerful regulators of lymphocyte signalling at the nuclear level. The bioactive forms of thyroid hormone and of several steroid hormones are generated locally by immunocytes. These important hormonal immunoregulators function both at systemic and local levels. Glucocorticoids are major regulators of cytokine production, and alpha-melanocyte-stimulating hormone functions as a powerful cytokine antagonist. The hormones secreted or regulated by the pituitary gland therefore regulate every level of immune activity, including the competence of lymphocytes to respond to immune/inflammatory stimuli, signal transduction, gene activation, the production and activity of cytokines and other immune effector functions.

Animals↗
PubMed1995

Localization of the N-methyl-D-aspartate R1 receptor subunit in specific anterior pituitary hormone cell types of the female rat.

N-methyl-D-aspartate (NMDA), a specific agonist of the NMDA-type glutamate receptor, has been shown to stimulate the release of several anterior pituitary hormones when administered in vivo. The primary site of action of NMDA has been suggested to be at the level of the hypothalamus via the control of hypothalamic releasing factors. However, recent studies have demonstrated that NMDA can exert stimulatory effects directly upon anterior pituitary cells perifused in vitro, suggesting that the anterior pituitary may also be a site of action for glutamate. Hence, the purpose of the present study was to determine whether the NMDA R1 receptor subunit is co-localized in specific hormone-secreting cells of the anterior pituitary. To achieve this aim, immunohistochemical studies were performed using an antibody specific for the NMDA R1 receptor subunit to stain sections from the pituitaries of steroid-treated ovariectomized immature rats. Double-immunohistochemistry was employed to demonstrate co-localization. The results of the studies revealed that moderate immunoreactive NMDA R1 receptor staining was observed in the anterior and intermediate lobe of the pituitary with little staining observed in the posterior lobe. Double-immunohistochemistry using antibodies for the NMDA R1 receptor subunit and specific anterior pituitary hormones revealed that the NMDA R1 receptor subunit is co-localized in many cell types of the anterior pituitary including LH (11.2%), FSH (9%), GH (4.6%), TSH (5.7%) and PRL cells (8%). Only one ACTH cell was found to co-localize the NMDA R1 receptor subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1979

Prostacyclin (PGI2) effects on anterior pituitary hormones in the rat in vivo.

Intravenous injection of 600 microgram PGE2 or PGI2 significantly increased serum LH and prolactin levels in estradiol treated ovariectomized rats. There was no effect on serum FSH concentration. PGE2 and PGI2 stimulated LH release in a non-dose dependent manner, while prolactin levels were positively correlated with the dose administered following PGI2 treatment. 6-keto-PGF1 alpha at a comparable dose had no effect on pituitary hormone levels. Subcutaneous administration of 1 mg/kg or 60 mg/kg PGI2 for seven days significantly depressed serum LH level both in male and female rats. These doses had no effect on serum FSH or prolactin levels.

Animals↗
PubMed1986

Anterior pituitary hormone responses to a kappa-opioid agonist in man.

The present study was designed to investigate pituitary hormone responses to a kappa-opiate receptor agonist in man. Normal men were given the racemic benzomorphan kappa-agonist MR 2033 or its levorotatory isomer MR 2034 iv. Plasma levels of PRL and GH markedly increased after injection of 3.5 micrograms/kg MR 2033 or 1.9 or 3.8 micrograms/kg MR 2034. These effects of MR 2033 were blocked by the opiate antagonist naloxone (10 mg), thereby demonstrating their mediation by opiate receptors. The kappa-agonist did not change plasma levels of LH and FSH. The secretion of TSH was significantly suppressed by MR 2033 and MR 2034, but this action was not antagonized by pretreatment with naloxone. The suppression of plasma TSH was, however, stereospecific since the (+)-isomer, MR 2035, did not affect TSH secretion. These data indicate that kappa-opiate receptors are located on neuronal pathways regulating GH, TSH, and PRL secretion. The pattern of pituitary responses elicited by the kappa-agonist differs from that of mu-opioid agonists, indicating differential endocrine functions for the endogenous agonists.

Adult↗
PubMed1986

Gamma amino butyric acid (GABA) controls anterior pituitary hormone secretion.

Intraventricular injection (3V) of GABA can lead to a dose-related increase in plasma LH in ovariectomized (OVX) and OVX, estrogen-primed animals. Since the effects were blocked by the GABA receptor antagonist, bicucculine (B), they appear to be specific. These alterations in plasma LH were accompanied by alterations in hypothalamic LHRH, dopamine (DA) and norepinephrine (NE) content which suggests roles for all three compounds in the genesis of the increase in plasma LH. Since the DA receptor blocker pimozide (P) failed to block the elevation in LH induced by GABA it appears that the effect of GABA on LH release is mediated by NE. Others have found that the GABA agonist, muscimol, can lower plasma LH under certain conditions. Consequently, it appears likely that there may be opposite actions of GABA on LHRH release depending on the site of action within the hypothalamus. Intravenous (iv) injection of B in OVX rats produced an initial fall in plasma LH followed by a prolonged rise which again suggests several sites of action of GABA on LH release. GABA had no effect on FSH release consistent with separate control of this hormone. 3V injection of various doses of GABA produced a dose-related lowering of plasma TSH in OVX rats which appeared to be mediated by the dopaminergic system since P abolished the TSH-lowering of GABA. Following iv injection of B in normal male rats, there was a dramatic decline in TSH suggesting that under these conditions GABA would have a stimulatory action. Similar results were seen in OVX rats. The results indicate an important stimulatory action of GABA on TSH release in both males and OVX females. Perhaps the discrepancy between the results with B and GABA can be explained again by multiple sites of action of GABA of opposite sign. 3V injection of GABA induced a dose-related stimulation of growth hormone (GH) secretion; however, more recent evidence from other laboratories suggests that under certain conditions GABA has an inhibitory role in GH secretion. Again, we speculate that GABA had dual sites of action of opposite sign to affect GH. In contrast to the effects of GABA on these pituitary hormones, it appears to have a direct inhibitory effect on prolactin (Prl) secretion via the lactotrophs. Both stimulatory and inhibitory actions of GABA have been found following its injection into the brain. Studies with iv B also support dual actions on Prl release.

Adrenocorticotropic Hormone↗
PubMed1989

Galanin and vasoactive intestinal polypeptide are colocalised with classical pituitary hormones and show plasticity of expression.

The identity of galanin- and vasoactive intestinal polypeptide-(VIP) immunoreactive (IR) cells in the rat anterior pituitary was investigated using immunocytochemistry and, since levels of both peptides are stimulated by oestrogen, the effect of oestrogen treatment and gonadectomy on the expression of both peptides was examined. In normal male rats, few galanin-IR and very few VIP-IR cells were found. Colocalisation studies performed on 2-microns serial paraffin sections revealed that in these animals galanin IR was present in somatotrophs and thyrotrophs. In normal females in dioestrus many lactotrophs, in addition to somatotrophs and thyrotrophs, expressed galanin, but very few VIP-IR cells were seen. In cryostat sections of normal rat pituitaries, slightly more VIP-IR cells were present. Oestrogen treatment in females produced an increase in frequency of galanin-IR cells, the vast majority of which were lactotrophs, and more VIP-IR cells, identified as lactotrophs, also appeared. VIP was present in a subset of galanin-IR lactotrophs after oestrogen treatment. After ovariectomy female pituitaries resembled those of normal males, with few galanin positive cells none of which were lactotrophs, and hardly any VIP-IR cells. Thus these two peptides are present in specific endocrine cell types of rat anterior pituitary and display plasticity of expression in different cell types under the influence of oestrogen. Their roles in control of pituitary hormone secretion are supported by these findings, and it is possible that both peptides act in a paracrine fashion within the pituitary.

Animals↗
PubMed2004

Pathophysiology of syndromic combined pituitary hormone deficiency due to a LHX3 defect in light of LHX3 and LHX4 expression during early human development.

The pathophysiology of combined pituitary hormone deficiency (CPHD) is just beginning to be elucidated, with mutations in genes encoding transcription factors expressed at different stages of pituitary development. Among them, the two closely related genes, LHX3 and LHX4, are believed to share redundant biological properties. The patients with a LHX3 mutation display a CPHD phenotype, associated with a rigid cervical spine. This latter feature, not reported in Lhx3-/- and Lhx4-/- mice nor in patients with a LHX4 defect, prompted us to study the molecular consequences of a previously identified LHX3 23-bp deletion and to determine the LHX3 and LHX4 expression patterns during early human development. This deletion, which results in the skipping of one coding exon, would lead to a protein with no transcriptional capability. Using in situ hybridization, we show that LHX3 and LHX4 are expressed in the developing human pituitary and along the rostro-caudal length of the spinal cord; here, both transcripts are detected in the ventral part giving rise to motorneurons and interneurons. However, whereas LHX3 is expressed at all stages studied, LHX4 expression is transient, and, at 6 weeks of development, is stronger at the caudal than at the cervical level.

Animals↗
PubMed1991

[Significance of the determination of gonadotropic pituitary hormones in different types of autonomic vascular dystonia].

Measurements were made of the content of gonadotropic pituitary hormones (prolactin/PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol in 151 children aged 11 to 15 years. Of these, there were 58 healthy children (24 boys and 34 girls), 51 children (25 boys and 26 girls) with vegetovascular dystonia (VVD) of the vagotonic type and 42 children (22 boys and 20 girls) with VVD of the sympathotonic type. It has been established that in VVD children, alterations in the hypothalamus-pituitary-gonadal system agreed with the general biological reactions of the body, while deviations in the LH and FSH levels as well as in estradiol got stabilized by 13 to 15 years. A positive correlation has been revealed between the high blood PRL level and the high tone of the sympathetic nervous system. In view of this fact the blood PRL content can serve an early diagnostic test for recognizing hypersympathicotonia in VVD children.

Adolescent↗