Neurotensin release from rat hypothalamus in vitro

1983 ◽  
Vol 97 (1) ◽  
pp. 105-111 ◽  
Author(s):  
K. I. J. Shennan ◽  
M. C. Sheppard
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Neuroendocrine Control ◽  
Rat Hypothalamus ◽  
Calcium Dependent ◽  
Tsh Secretion ◽  
Dose Dependent

Neurotensin is a hypothalamic peptide which inhibits secretion of TSH in the rat in vivo. We have demonstrated a calcium-dependent release of neurotensin from incubated rat hypothalamus in response to depolarizing stimuli, as well as a dose-dependent stimulatory effect of tri-iodothyronine (T3) on neurotensin secretion. We suggest that part of the neuroendocrine control of TSH secretion involves the interaction of T3, neurotensin and TSH; the presence of neurotensin in extracts of anterior pituitary gland is further evidence for its hypophysiotrophic role.

scholarly journals Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

1975 ◽  
Vol 67 (2) ◽  
pp. 469-476 ◽  
Author(s):  
WH Fletcher ◽  
NC Anderson ◽  
JW Everett
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
In Vitro Study ◽  
Anterior Pituitary Gland ◽  
Stimulus Secretion Coupling ◽  
Unpublished Observation ◽  
Cellular Ca

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.

scholarly journals In Vivo and In Vitro Arsenic Exposition Induces Oxidative Stress in Anterior Pituitary Gland

2016 ◽  
Vol 35 (4) ◽  
pp. 463-475 ◽  
Author(s):  
Sonia A. Ronchetti ◽  
María S. Bianchi ◽  
Beatriz H. Duvilanski ◽  
Jimena P. Cabilla
Keyword(s):  
Oxidative Stress ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inorganic Arsenic ◽  
Anterior Pituitary Gland ◽  
Pituitary Cells ◽  
Prolactin Release ◽  
Stress Responsive Genes

Inorganic arsenic (iAs) is at the top of toxic metalloids. Inorganic arsenic-contaminated water consumption is one of the greatest environmental health threats worldwide. Human iAs exposure has been associated with cancers of several organs, neurological disorders, and reproductive problems. Nevertheless, there are no reports describing how iAs affects the anterior pituitary gland. The aim of this study was to investigate the mechanisms involved in iAs-mediated anterior pituitary toxicity both in vivo and in vitro. We showed that iAs administration (from 5 to 100 ppm) to male rats through drinking water increased messenger RNA expression of several oxidative stress-responsive genes in the anterior pituitary gland. Serum prolactin levels diminished, whereas luteinizing hormone (LH) levels were only affected at the higher dose tested. In anterior pituitary cells in culture, 25 µmol/L iAs significantly decreased prolactin release in a time-dependent fashion, whereas LH levels remained unaltered. Cell viability was significantly reduced mainly by apoptosis evidenced by morphological and phosphatidylserine externalization studies. This process is characterized by early depolarization of mitochondrial membrane potential and increased levels of reactive oxygen species. Expression of some key oxidative stress-responsive genes, such as heme oxygenase-1 and metallothionein-1, was also stimulated by iAs exposure. The antioxidant N-acetyl cysteine prevented iAs-induced effects on the expression of oxidative stress markers, prolactin release, and apoptosis. In summary, the present work demonstrates for the first time that iAs reduces prolactin release both in vivo and in vitro and induces apoptosis in anterior pituitary cells, possibly resulting from imbalanced cellular redox status.

RELATIVE ACTIVITY, PLASMA ELIMINATION AND TISSUE DEGRADATION OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE AND CERTAIN OF ITS ANALOGUES

1979 ◽  
Vol 80 (1) ◽  
pp. 141-152 ◽  
Author(s):  
A. D. SWIFT ◽  
D. B. CRIGHTON
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inverse Correlation ◽  
Anterior Pituitary Gland ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh

The abilities of three nonapeptide analogues of synthetic luteinizing hormone releasing hormone (LH-RH) to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in anoestrous and cyclic ewes were examined, as were their elimination from the plasma in vivo and degradation by extracts of the hypothalamus, anterior pituitary gland, lung, kidney, liver and plasma in vitro. In all cases, comparisons were made with synthetic LH-RH. When injected i.v. into mature ewes as a single dose, the potencies of the analogues were graded and Des Gly-NH210 LH-RH ethylamide was found to be the least potent. It was not possible to demonstrate any significant increase in the potency of this analogue over LH-RH, although a trend was apparent with each parameter examined. [d-Ser(But)6] Des Gly-NH210 LH-RH ethylamide had the greatest potency. There were no differences between the responses of anoestrous ewes and those of ewes treated on day 10 of the oestrous cycle. None of the analogues had a rate of elimination from the plasma different from that of LH-RH during either the first or the second components of the biphasic disappearance curve. The incubation of LH-RH with tissue extracts showed that extracts of the hypothalamus and anterior pituitary gland degraded LH-RH to a similar extent. Both the hypothalamic and anterior pituitary gland extracts degraded more LH-RH than did lung extract, which in turn destroyed more LH-RH than did extracts of kidney or liver tissue. The degradative abilities of kidney and liver extracts did not differ from each other. Plasma failed to degrade LH-RH or the analogues. Although LH-RH was rapidly destroyed by hypothalamic extract in vitro, of the analogues, only Des Gly-NH210 LH-RH ethylamide was degraded. The anterior pituitary gland and kidney extracts failed to degrade [d-Ser6] Des Gly-NH210 LH-RH ethylamide and [d-Ser(But)6] Des Gly-NH210 LH-RH ethylamide as rapidly as LH-RH. Extracts of liver and lung were incapable of catabolizing any of the analogues. There was an inverse correlation between the LH- and FSH-releasing potency of an analogue and its rate of degradation by anterior pituitary gland extract. The slower rates of catabolism of certain analogues of LH-RH by the anterior pituitary gland may explain their increased LH- and FSH-releasing potency.

Characteristics of corticosteroid inhibition of adrenocorticotrophin release from the anterior pituitary gland of the rat

1984 ◽  
Vol 102 (1) ◽  
pp. 33-42 ◽  
Author(s):  
S. N. Mahmoud ◽  
S. Scaccianoce ◽  
P. R. Scraggs ◽  
S. A. Nicholson ◽  
B. Gillham ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Rate Sensitivity ◽  
Inhibitory Effect ◽  
Experimental Models ◽  
Delayed Feedback ◽  
Anterior Pituitary Gland ◽  
Intact Rats

ABSTRACT The occurrence and nature of corticosteroid inhibition of ACTH secretion at the rat anterior pituitary gland was investigated using three experimental models: animals bearing lesions of the basal hypothalamus, and two preparations of the gland incubated in vitro; these were tissue segments and collagenase-dispersed cells. Release of ACTH in the experiments was provoked using one of three distinct stimuli: acid extracts of whole hypothalami, corticotrophin releasing activity released by serotonin from hypothalami incubated in vitro and synthetic ovine corticotrophin releasing factor. Irrespective of whether ACTH was measured directly by radioimmunoassay (in the experiments in vitro) or indirectly in terms of corticosterone production (in the lesioned animals), its stimulated release from the anterior pituitary gland was inhibited by corticosterone. Two phases of inhibition were observed; these had some of the characteristics inferred previously from experiments with intact animals and designated fast feedback and delayed feedback. However, the fast feedback demonstrable in lesioned animals did not show the rate-sensitivity shown previously in intact animals. 11-Deoxycortisol (or 11-deoxycorticosterone) and prednisolone proved to be agonists of corticosterone in provoking fast feed-back in lesioned animals, whereas they had been shown respectively to act as an antagonist or to have no effect in intact rats. Several steroids were able to cause delayed feedback in lesioned rats, but beclomethasone dipropionate (shown to be an agonist of corticosterone in intact rats) proved to have no inhibitory effect at the anterior pituitary gland of lesioned animals. It is concluded that the dynamics of corticosteroid feedback mechanisms at the anterior pituitary gland, as indicated by experiments in lesioned animals, differ from those operative in the intact animals. Other work suggests that a more important site for such inhibitory mechanisms in vivo is the hypothalamus. J. Endocr. (1984) 102, 33–42

EFFECTS OF OESTRADIOL, HYPOTHALAMIC EXTRACTS AND LUTEINIZING HORMONE RELEASING HORMONE ON RAT ANTERIOR PITUITARY GLAND GONADOTROPHIN RELEASE IN VITRO BEFORE AND AFTER THE PREOVULATORY LUTEINIZING HORMONE SURGE AT PRO-OESTRUS

1981 ◽  
Vol 90 (3) ◽  
pp. 345-354 ◽  
Author(s):  
KATHLEEN A. ELIAS ◽  
C. A. BLAKE
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Lh Surge ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Lh Releasing Hormone

Changes at the anterior pituitary and/or hypothalamic levels which result in selective FSH release during late pro-oestrus in the cyclic rat were investigated. The possible involvement of decreasing serum concentrations of oestrogen during pro-oestrus in such changes was studied. Rats were decapitated at 12.00 h on pro-oestrus, before the onset of the LH surge and first phase of FSH release, or at 24.00 h on pro-oestrus, shortly after the onset of the second or selective phase of FSH release. Other rats were given oestrogen (OE2) at 14.00 h and killed at 24.00 h pro-oestrus. Paired hemi-anterior pituitary glands were incubated with vehicle or OE2 with or without synthetic LH-releasing hormone (LH-RH) or hypothalamic acid extracts prepared from rats killed at 12.00 or 24.00 h on pro-oestrus. At 24.00 h pro-oestrus, serum FSH concentration was high while serum LH concentration was low regardless of whether rats were given OE2. Glands collected and incubated at 24.00 h released more FSH and less LH than did glands collected and incubated at 12.00 h pro-oestrus. Administration of OE2 in vivo and/or in vitro did not affect these responses. The increments in LH and FSH release attributed to LH-RH or hypothalamic extracts in the glands incubated at 24.00 h were not different from those of the glands incubated at 12.00 h. Also, the hypothalamic extracts prepared from rats killed at 24.00 h were no more effective than the extracts prepared from rats killed at 12.00 h in releasing LH or FSH from glands incubated at 12.00 or 24.00 h pro-oestrus. Administration of OE2 in vivo caused a small suppression of LH-RH-induced FSH release. We suggest that a change occurs at the level of the anterior pituitary gland during the period of the LH surge and first phase of FSH release to increase basal FSH secretion selectively and cause, at least in part, the second phase of increased serum FSH. This change is not mediated by a decrease in serum oestrogen concentration. We failed to observe any evidence that LH-RH causes preferential FSH release during late pro-oestrus or that a hypothalamic peptide with a preferential FSH releasing ability is involved in FSH release at this time.

Role of serotonin in the control of secretion of corticotrophin releasing factor

1982 ◽  
Vol 93 (2) ◽  
pp. 151-160 ◽  
Author(s):  
M. C. Holmes ◽  
G. Di Renzo ◽  
U. Beckford ◽  
B. Gillham ◽  
M. T. Jones
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Synaptic Cleft ◽  
Anterior Pituitary Gland ◽  
Intraventricular Administration ◽  
Rat Hypothalamus ◽  
Corticotrophin Releasing Factor ◽  
The Status

The status of serotonin as a putative neurotransmitter involved in the control of the secretion of corticotrophin-releasing activity from the rat hypothalamus has been further investigated. The experimental model used for the investigation was the rat hypothalamus incubated in vitro. It was confirmed that serotonin causes a dose-related release of corticotrophin-releasing activity from the tissue and it was shown that this effect was mimicked by the addition to the tissue of chlorimipramine or d-fenfluramine, two drugs expected to cause an increase in the concentration of serotonin in the synaptic cleft. The effect of the latter drug was greatly reduced by the simultaneous addition of either methysergide or metergoline. Destruction of serotonin-containing nerve terminals in the hypothalamus was caused by the intraventricular administration of the neurotoxic drug 5,7-dihydroxytryptamine. This treatment resulted in an 84% reduction of the serotonin concentration in the hypothalamus 12 days later. Hypothalami taken from animals 12 days after treatment with the drug secreted corticotrophin-releasing activity in basal amounts equal to those found in tissues taken from control rats, but showed supersensitivity in response to added serotonin. No such supersensitivity was seen in response to d-fenfluramine and a diminished response to chlorimipramine was noted. Despite its intraventricular route of administration, 5,7dihydroxytryptamine was found to increase the sensitivity of segments of anterior pituitary gland in vitro to low doses of preparations containing corticotrophin releasing factor. These results are consistent with the view that endogenous serotonin can act as a stimulator of the secretion of corticotrophin-releasing activity from the rat hypothalamus. They also suggest that conclusions about the control of the release of this trophic material inferred from measurements of corticotrophin or corticosterone in the circulation must be viewed with caution when the drug 5,7-dihydroxytryptamine has been used, because of the development of supersensitivity both in the hypothalamus and in the anterior pituitary gland.

Effect of hypothalamic neuropeptides on corticotrophin release from quarters of rat anterior pituitary gland in vitro

1984 ◽  
Vol 100 (2) ◽  
pp. 219-226 ◽  
Author(s):  
S. A. Nicholson ◽  
T. E. Adrian ◽  
B. Gillham ◽  
M. T. Jones ◽  
S. R. Bloom
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Low Dose ◽  
Physiological Role ◽  
Anterior Pituitary Gland ◽  
High Concentration ◽  
Response Curves ◽  
Corticotrophin Releasing Factor ◽  
Basal Release

ABSTRACT The effect of six hypothalamic peptides on the basal release of ACTH and that induced by arginine vasopressin (AVP) or by ovine corticotrophin releasing factor (oCRF) from fragments of the rat anterior pituitary gland incubated in vitro was investigated. Dose–response curves to AVP and to oCRF were obtained, and the response to a low dose of oCRF was potentiated by a low dose of AVP. Basal release of ACTH was not affected by any of the peptides in concentrations in the range 10−12 to 10−6 mol/l, and only substance P (SP) and somatostatin (SRIF) inhibited significantly the response to oCRF in a dose-related manner. The responses to a range of doses of oCRF or AVP were reduced by 10−8 and 10 − 6 mol SP or SRIF/1, and to a greater extent by the higher dose. Except in the case of 10−6 mol SRIF/1 on the response to AVP, the response was not further diminished by preincubation of the tissue with the peptide before the stimulating agent was added. The inhibition of the responses to AVP or oCRF by 10−9 mol SP/1 was not potentiated by its combination with either 5 × 10−10 or 10−8 mol SRIF/1; the inhibitory effects were merely additive. The results suggest that although SRIF and SP are able to modulate the release of ACTH from the anterior pituitary gland, they do so only at a high concentration. In the case of SRIF these concentrations are several orders of magnitude higher than those reported to be present in the hypophysial portal blood and therefore a physiological role for this peptide in the control of ACTH secretion is unlikely. J. Endocr. (1984) 100, 219–226

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