PITUITARY HORMONE PRODUCTION AND RELEASE IN THE THYROIDECTOMIZED RAT AFTER THYROXINE ADMINISTRATION

1963 ◽  
Vol 42 (2) ◽  
pp. 275-292 ◽  
Author(s):  
A. N. Contopoulos ◽  
A. A. Koneff ◽  
J. D. Jameson
Keyword(s):  
Effective Dose ◽  
Normal Control ◽  
Anterior Pituitary ◽  
Female Rats ◽  
Pituitary Hormone ◽  
Hormone Production ◽  
Minimal Effective Dose ◽  
Thyrotrophic Hormone ◽  
Hormonal Content ◽  
Long Evans

ABSTRACT Female rats of the Long-Evans strain were thyroidectomized at 35–40 days of age and 56 days later were placed into three groups each receiving injections 1, 2 or 3 μg of thyroxine per day for four days. Uninjected thyroidectomized and normal rats were used as controls. Twenty-four hours after the last injection the pituitaries and plasma were bio-assayed as a measure of pituitary hormone production and secretion. The minimal effective dose in hypophysectomized recipients in terms of whole anterior pituitary, or fraction thereof, are as follows: normal control pituitary – TSH, 1/16; FSH, < 3; ICSH, 1; GH> 1/16; thyroidectomy – TSH, 1/8–1/4; FSH, > 5; ICSH, > 5; GH, 3. Thyroxine administration restored the TSH pituitary content to normal at 1 μg dose, and increased it further at the 2 and 3 μg dose. The pituitary content of GH increased from the post-thyroidectomy levels to near normal levels with increasing doses of thyroxine. The ICSH content of the pituitary was influenced by the administration of thyroxine but no effect was obvious in FSH content. GH was not detectable in plasma of thyroidectomized rats but was present in the plasma of animals receiving 2 or 3 μg of thyroxine. Thyrotrophic hormone content of plasma was decreased after administration of thyroxine. Gonadotrophin was not detected in any plasma. The above changes in hormonal content preceded the reappearance of normal pituitary cytology.

scholarly journals Estrogen mediates sex differences in preoptic neuropeptide and pituitary hormone production in medaka

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Junpei Yamashita ◽  
Yuji Nishiike ◽  
Thomas Fleming ◽  
Daichi Kayo ◽  
Kataaki Okubo
Keyword(s):  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Sexually Dimorphic ◽  
Hormone Production ◽  
Anterior Pituitary Hormones ◽  
Vertebrate Brain ◽  
Pituitary Adenylate Cyclase ◽  
Evolutionarily Conserved ◽  
Sexually Dimorphic Expression

AbstractThe preoptic area (POA) is one of the most evolutionarily conserved regions of the vertebrate brain and contains subsets of neuropeptide-expressing neurons. Here we found in the teleost medaka that two neuropeptides belonging to the secretin family, pituitary adenylate cyclase-activating polypeptide (Pacap) and vasoactive intestinal peptide (Vip), exhibit opposite patterns of sexually dimorphic expression in the same population of POA neurons that project to the anterior pituitary: Pacap is male-biased, whereas Vip is female-biased. Estrogen secreted by the ovary in adulthood was found to attenuate Pacap expression and, conversely, stimulate Vip expression in the female POA, thereby establishing and maintaining their opposite sexual dimorphism. Pituitary organ culture experiments demonstrated that both Pacap and Vip can markedly alter the expression of various anterior pituitary hormones. Collectively, these findings show that males and females use alternative preoptic neuropeptides to regulate anterior pituitary hormones as a result of their different estrogen milieu.

THE MECHANISM OF THE INDUCTION OF OVULATION BY OESTROGENS

1965 ◽  
Vol 33 (3) ◽  
pp. 491-499 ◽  
Author(s):  
F. DÖCKE ◽  
G. DÖRNER
Keyword(s):  
Effective Dose ◽  
Corpus Luteum ◽  
Anterior Pituitary ◽  
Anterior Hypothalamus ◽  
Female Rats ◽  
Main Site ◽  
Induction Of Ovulation ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Electrolytic Lesions

SUMMARY To study the positive feed-back mechanism by which oestrogen induces corpus luteum formation, electrolytic lesions were placed in different parts of the anterior hypothalamus of prepubertal female rats which were then injected with oestradiol benzoate. Ovarian luteinization did not occur when the main parts of the suprachiasmatic nuclei or of the medial preoptic area had been destroyed. Oestradiol benzoate was implanted stereotaxically into the brain and the anterior pituitary of immature female rats. Whereas 1/25 of the subcutaneously effective dose had to be implanted into the anterior hypothalamus, 1/100 of the peripherally effective dose introduced into the adenohypophysis was sufficient to induce corpus luteum formation in most of the treated animals. The results suggest that, although the anterior hypothalamus is necessary for this positive feed-back mechanism, the anterior pituitary may be the main site of action of oestrogen. Oestrogen may increase the hypophysial sensitivity to the hypothalamic gonadotrophin-releasing factor. Thus an enhanced gonadotrophin secretion may result, sufficient for the induction of ovulation. The possibility is discussed that this positive feed-back mechanism is also essential for the induction of ovulation in women.

scholarly journals The Musashi1 RNA-Binding Protein Functions as a Leptin-Regulated Enforcer of Pituitary Cell Fate and Hormone Production

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A654-A654
Author(s):  
Jewel Banik* ◽  
Juchan Lim* ◽  
Hardy L Linda ◽  
Angela Katherine Odle ◽  
Gwen V Childs ◽  
...  
Keyword(s):  
Cell Fate ◽  
Anterior Pituitary ◽  
Binding Protein ◽  
Mrna Translation ◽  
Pituitary Cell ◽  
Pituitary Hormone ◽  
Hormone Production ◽  
Lineage Specification ◽  
Regulatory Phosphorylation ◽  
Translational Activation

Abstract The pituitary gland is the major endocrine organ that produces and secretes hormones in response to hypothalamic signals to regulate important processes like growth, reproduction, and stress. The anterior pituitary adapts to metabolic and reproductive needs by exhibiting cellular plasticity, resulting in altered hormone production and secretion. The adipokine, leptin, serves a critical role to couple energy status to pituitary function. We have recently reported that the cell fate determinant, Musashi, functions as a post-transcriptional regulator of target mRNA translation in the mouse pituitary and have speculated that Musashi may modulate pituitary cell plasticity. However, the underlying mechanisms governing such pituitary plasticity are not fully understood. Musashi is an mRNA binding protein that is required for self-renewal, proliferation, and to control the differentiation of stem and progenitor cells. We have recently shown that Musashi is expressed in Sox2+ pituitary stem cells and surprisingly, we also found Musashi expression in all differentiated hormone expressing cell lineages in the adult anterior pituitary. The role of Musashi in these mature differentiated cells is unknown. We have observed that a range of critical pituitary mRNAs, including the lineage specification transcription factors Prop1 and Pou1f1, as well as hormone mRNAs including Tshb, Prl, and Gnrhr, all contain consensus Musashi binding elements (MBEs) in their 3’ untranslated regions (3’ UTRs). Using RNA electrophoretic mobility shift assays (EMSAs) and luciferase mRNA translation reporter assays we show that Musashi binds to these mRNAs and exerts inhibitory control of mRNA translation. Moreover, we determined that leptin stimulation opposes the ability of Musashi to exert translational repression of the Pou1f1 and Gnrhr 3’ UTRs. This de-repression does not require regulatory phosphorylation of Musashi on two conserved C-terminal serine residues. Interestingly in the same cell assay system, Musashi exerts translational activation of the Prop1 3’ UTR. We observed that this translational activation requires Musashi phosphorylation on the two regulatory C-terminal serine residues, consistent with the requirement for regulatory phosphorylation to drive translational activation of Musashi target mRNAs during Xenopus oocyte cell maturation. The distinction between MBEs in 3’ UTRs that exert repression (Pou1f1, Prl, Tshb, and Gnrhr) and the Prop1 3’ UTR that directs translational activation is under investigation. We propose that Musashi acts as a bifunctional regulator of pituitary hormone production and lineage specification and may function to maintain pituitary hormone plasticity in response to changing organismal needs.

scholarly journals The regulation of GH secretion by sex steroids

2004 ◽  
pp. U95-100 ◽  
Author(s):  
JA Chowen ◽  
LM Frago ◽  
J Argente
Keyword(s):  
Sex Steroids ◽  
Anterior Pituitary ◽  
Primary Cultures ◽  
Female Rats ◽  
Sex Steroid ◽  
Pituitary Hormone ◽  
Mrna Levels ◽  
Hormone Release ◽  
Gh Secretion ◽  
Anterior Pituitary Hormone

Gonadal sex steroids modulate GH synthesis and secretion with effects on both the hypothalamus and anterior pituitary. In the post-pubertal animal, androgens and oestrogens modulate hypothalamic somatostatin (SS) and GHRH synthesis respectively. These effects may be direct as SS neurons express the androgen receptor and many GHRH neurons are oestrogen receptor positive. The neonatal steroid environment modulates the number of GHRH neurons in the adult hypothalamus, as well as their responsivity to post-pubertal steroids. Furthermore, both neonatal and post-pubertal steroids modulate hypothalamic synaptic organisation affecting the number of synaptic inputs and the morphology of glial cells. This in turn has important effects on the ability of the hypothalamus to drive the secretory pulsatility of anterior pituitary hormone release. At the level of the somatotroph, androgens and oestrogens have been reported to stimulate, inhibit or have no effect on GH synthesis. In primary cultures, we found no effect of either androgens or oestrogens on GH mRNA levels. However, the sex steroid environment significantly modified the response of somatotrophs to SS. Furthermore, males have more somatotrophs compared with female rats and this partially depends on the neonatal sex steroid environment. In conclusion, sex steroids have both organisational and activational effects on the GH axis. These effects range from modulating the number of hypothalamic neurons controlling GH secretion, their responsiveness to later steroids, and the synaptic connectivity and neuropeptide production, to modulation of somatotroph numbers in the anterior pituitary and their responsiveness to inputs controlling GH synthesis and secretion.

scholarly journals Effects of Melatonin on Anterior Pituitary Plasticity: A Comparison Between Mammals and Teleosts

2021 ◽  
Vol 11 ◽  
Author(s):  
Elia Ciani ◽  
Trude M. Haug ◽  
Gersende Maugars ◽  
Finn-Arne Weltzien ◽  
Jack Falcón ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Future Research ◽  
Pituitary Hormone ◽  
Hormone Production ◽  
Physiological Processes ◽  
Important Target ◽  
Specific Receptors ◽  
Positive And Negative Feedback

Melatonin is a key hormone involved in the photoperiodic signaling pathway. In both teleosts and mammals, melatonin produced in the pineal gland at night is released into the blood and cerebrospinal fluid, providing rhythmic information to the whole organism. Melatonin acts via specific receptors, allowing the synchronization of daily and annual physiological rhythms to environmental conditions. The pituitary gland, which produces several hormones involved in a variety of physiological processes such as growth, metabolism, stress and reproduction, is an important target of melatonin. Melatonin modulates pituitary cellular activities, adjusting the synthesis and release of the different pituitary hormones to the functional demands, which changes during the day, seasons and life stages. It is, however, not always clear whether melatonin acts directly or indirectly on the pituitary. Indeed, melatonin also acts both upstream, on brain centers that control the pituitary hormone production and release, as well as downstream, on the tissues targeted by the pituitary hormones, which provide positive and negative feedback to the pituitary gland. In this review, we describe the known pathways through which melatonin modulates anterior pituitary hormonal production, distinguishing indirect effects mediated by brain centers from direct effects on the anterior pituitary. We also highlight similarities and differences between teleosts and mammals, drawing attention to knowledge gaps, and suggesting aims for future research.

A POSSIBLE MECHANISM OF THE OVULATION-INHIBITING EFFECT OF CHLORMADINONE ACETATE IN THE RAT

1968 ◽  
Vol 41 (3) ◽  
pp. 353-362 ◽  
Author(s):  
F. DÖCKE ◽  
G. DÖRNER ◽  
K.-H. VOIGT
Keyword(s):  
Effective Dose ◽  
Median Eminence ◽  
Anterior Pituitary ◽  
Anterior Hypothalamus ◽  
Female Rats ◽  
Main Site ◽  
Chlormadinone Acetate ◽  
Inhibiting Effect ◽  
Competitive Antagonism ◽  
Site Of Action

SUMMARY To study the mechanism of the ovulation-inhibiting effect of chlormadinone acetate, different quantities of this progestogen were implanted into one or both ovaries of dioestrous female rats. Introduction of the subcutaneously effective dose into one ovary suppressed ovulation in both, but implantation of half of this quantity did not influence spontaneous ovulation. On the other hand, 1/100 of the subcutaneously effective dose, implanted into the medio-basal hypothalamus or the anterior pituitary of adult dioestrous female rats, and of prepubertal females simultaneously injected with oestradiol benzoate, inhibited spontaneous and oestrogen-induced ovulations respectively. In juvenile rats the main site of action was the median eminence—anterior pituitary region. Chlormadinone was then implanted into the anterior hypothalamus or the anterior pituitary of adult dioestrous rats, and the median eminence was electrically stimulated during the 'critical period' in pro-oestrus. Since implants in the adenohypophysis prevented ovulation whereas implants in the anterior hypothalamus did not, a hypophysial site of action is suggested. On the basis of these results and of former findings on the action of oestrogens in ovulation, a hypothesis involving a competitive antagonism between oestrogen and progestogen at the hypophysial level is advanced to explain the acute ovulatory effects of these steroids.

CHANGES IN THE LUTEINIZING HORMONE RELEASING ACTIVITY OF THE HYPOTHALAMUS, AND IN PITUITARY GLAND AND PLASMA LUTEINIZING HORMONE DURING THE OESTROUS CYCLE OF THE SHEEP

1973 ◽  
Vol 58 (3) ◽  
pp. 377-385 ◽  
Author(s):  
D. B. CRIGHTON ◽  
BARBARA M. HARTLEY ◽  
G. E. LAMMING
Keyword(s):  
Ascorbic Acid ◽  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Effective Dose ◽  
Anterior Pituitary ◽  
Ovarian Activity ◽  
Factor Activity ◽  
Minimal Effective Dose ◽  
Pituitary Tissue ◽  
Male Sheep

SUMMARY Thirty ewes with regular oestrous cycles were divided into six groups for slaughter relative to the time of first acceptance of the ram. The slaughter times were: 0 h (in practice within 40 min of onset of oestrus), 6, 12 and 36 h after onset and days 10 and 16 of the cycle. The hypothalamus was removed and the luteinizing hormone (LH) releasing factor activity extracted with 0·1 m-HCl. The extracts were tested for LH releasing activity by adding them to the medium in which anterior pituitary tissue from castrated male sheep was incubated. The LH content of the medium was measured by the ovarian ascorbic acid depletion method (Parlow, 1958). The activity of the extract from the group slaughtered on day 16 of the cycle was high (minimal effective dose (MED) = 0·00625 hypothalamic equivalents (HE)). The potency declined with the onset of oestrus and remained low at 6 and 36 h after onset (MED in each case 0·025 HE) with intermediate potencies at 12 h and 10 days after onset (MED in each case 0·0125 HE). These changes are compared with changes in the LH content of the pituitary gland (bioassay) and of the plasma (radioimmunoassay) and with parameters of the ovarian activity of the animals.

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