Alteration by thyrotrophin-releasing hormone of heterogeneous components associated with thyrotrophin biosynthesis in the rat anterior pituitary gland

1984 ◽  
Vol 103 (2) ◽  
pp. 165-171 ◽  
Author(s):  
M. Mori ◽  
M. Murakami ◽  
T. Iriuchijima ◽  
H. Ishihara ◽  
I. Kobayashi ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
De Novo ◽  
Close Association ◽  
Anterior Pituitary Gland ◽  
Male Rats ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Pituitary Glands

ABSTRACT An influence of thyrotrophin-releasing hormone (TRH) on TSH heterogeneity in close association with de-novo biosynthesis was studied in rat anterior pituitary glands. Hemipituitary glands from adult male rats were incubated in Krebs–Henseleit–glucose media containing [3H]glucosamine and [14C]alanine for 3 and 6 h in the presence or absence of 10 ng TRH per ml. Fractions of TSH in the pituitary extracts were obtained using affinity chromatography coupled with an anti-rat TSH globulin. These TSH fractions were analysed by isoelectric focusing. The control pituitary glands were composed of four component peaks (isoelectric point (pI) 8·7, 7·8, 5·3 and 2·5) of [3H]glucosamine and [14C]alanine incorporated into TSH, and the amounts of radioactivity of these components were increased with the incubation time. Of these peaks, radioactive components of pI 8·7 and 7·8 coincided with the non-radioactive TSH components measured by radioimmunoassay. Addition of TRH increased incorporation of [14C]alanine into TSH in each of the components to a greater extent than that of [3H]glucosamine. In addition, new components with pI 7·2, 6·5 and 6·2, each component corresponding to each unlabelled TSH component, were demonstrated in the presence of TRH. Because addition of TRH did not change the amounts of [14C]alanine-labelled TSH in the media, the newly formed components were assumed to be connected with protein synthesis occurring in the anterior pituitary gland, which may be specific substances in response to TRH administration. These results indicate that TRH principally elicits an increase in protein synthesis in TSH at the anterior pituitary level, resulting in an alteration of TSH heterogeneity. J. Endocr. (1984) 103, 165–171

Pro-oestrous-specific role for polyamines in mediating the secretion of prolactin induced by thyrotrophin-releasing hormone in the rat

1993 ◽  
Vol 137 (1) ◽  
pp. 133-139 ◽  
Author(s):  
G. A. Wynne-Jones ◽  
A. M. Gurney
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Anterior Pituitary Gland ◽  
Oestrous Cycle ◽  
Male Rats ◽  
Pituitary Cells ◽  
Plasma Prolactin ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone

ABSTRACT The activity of ornithine decarboxylase (ODC) in the rat anterior pituitary gland varies during the oestrous cycle, with a rise in activity seen at pro-oestrus. This enzyme, which is rate-limiting for the synthesis of the polyamines, can be specifically and irreversibly blocked by α-difluoromethylornithine (DFMO). A previous study showed that when this drug was administered to rats in vivo on the afternoon of pro-oestrus, it suppressed the normal surge in plasma prolactin levels that occurred later that day. The effect of DFMO was associated with reduced levels of putrescine in the anterior pituitary gland, suggesting that ODC activity in the lactotroph might be involved in the prolactin surge. We have examined the effects of DFMO on the secretion of prolactin from anterior pituitary cells, isolated either from male rats or from females at different stages of the oestrous cycle. The drug was found to reduce prolactin secretion stimulated by thyrotrophin-releasing hormone (TRH), but only in cells isolated from pro-oestrous animals and only for 2 days after cell isolation. Basal secretion was unaffected by DFMO. The results imply that ODC is important for TRH-stimulated prolactin secretion at pro-oestrus, and it is specific for pro-oestrus. The prolactin surge could therefore be influenced by this ODC-dependent effect of TRH. The pro-oestrous-specific response to TRH may be a consequence of the increased ODC activity seen at this time. Alternatively, the increased ODC activity could be a consequence of coupling to TRH receptors, which are known to increase in number at pro-oestrus. Journal of Endocrinology (1993) 137, 133–139

THYROTROPHIN RELEASING HORMONE-INDUCED GROWTH HORMONE AND PROLACTIN RELEASE: PHYSIOLOGICAL STUDIES IN INTACT RATS AND IN HYPOPHYSECTOMIZED RATS BEARING AN ECTOPIC PITUITARY GLAND

1977 ◽  
Vol 72 (3) ◽  
pp. 301-311 ◽  
Author(s):  
A. E. PANERAI ◽  
IRIT GIL-AD ◽  
DANIELA COCCHI ◽  
V. LOCATELLI ◽  
G. L. ROSSI ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Time Lapse ◽  
Anterior Pituitary Gland ◽  
Plasma Prolactin ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Clear Cut ◽  
Urethane Anaesthesia ◽  
Releasing Effect

SUMMARY To determine how the sensitivity of the ectopic anterior pituitary gland to the GH-releasing effect of thyrotrophin releasing hormone (TRH) might be affected by the time lapse from transplantation, TRH (0·15 and 0·6 μg) was injected i.v. into hypophysectomized (hypox)-transplanted rats under urethane anaesthesia 1,3, 8,15, 30 and 60 days after transplantation, and plasma samples were taken 5 and 10 min later. Baseline GH values gradually decreased with time from about 16·0 ng/ml (1 day) to about 3·0 ng/ml (30 and 60 days). The TRH-induced GH release was absent 1 day after transplantation, present only with the higher TRH dose 3 and 8 days after transplantation, and clearly elicitable, also with the lower TRH dose (0·15 μg), from 15 up to 60 days. Determination of plasma prolactin concentrations showed a decline from about 85·0 ng/ml (1 day) to about 32·0 ng/ml (8 days); subsequently (15–60 days) prolactin values stabilized. Plasma prolactin levels increased 15 and 60 days after transplantation only when a dose of 0·6 μg TRH was given. In intact weight-matched rats, TRH induced a GH response only at the dose of 1·2 μg while a short-lived but clear-cut prolactin response could be obtained even with the 0·3 μg dose. The present results indicate that: (1) disconnexion between the central nervous system and the anterior pituitary gland greatly enhances GH responsiveness while blunting prolactin responsiveness to TRH; (2) the sensitivity of the anterior pituitary gland to the GH-releasing effect of TRH increases with time from transplantation; (3) TRH is a more effective prolactin-than GH-releaser on the pituitary gland in situ.

Relationships among release of prolactin, synthesis of DNA and growth of the anterior pituitary gland of the rat: effects of oestrogen and sulpiride

1982 ◽  
Vol 94 (1) ◽  
pp. 1-10 ◽  
Author(s):  
G. A. Jahn ◽  
G. A. Machiavelli ◽  
L. E. Kalbermann ◽  
I. Szijan ◽  
G. E. Alonso ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Single Injection ◽  
Serum Levels ◽  
Anterior Pituitary Gland ◽  
Male Rats ◽  
Maximum Increase ◽  
End Of Treatment ◽  
Pituitary Glands ◽  
Prolactin Synthesis

The effect of daily injections of sulpiride was compared with that of a single injection of the drug in male rats which had been treated with oestradiol diundecenoate for various periods of time. We studied the effect of the different treatments on weight of the pituitary gland, concentration of prolactin and incorporation of [3H]thymidine into DNA in the pituitary gland and on serum levels of prolactin. Administration of the oestrogen produced a marked increase in the synthesis of DNA at day 7. The stimulation diminished at day 21 and was not significant at day 45. The maximum increase in the concentration of prolactin in serum and pituitary glands was observed during the first 7 days (approximately 400 and 150% respectively) and in the weight of the anterior pituitary gland after 21 days of treatment (approximately 107%). A single injection of sulpiride markedly stimulated the release of prolactin and the synthesis of DNA at day 7. Both these effects diminished at day 21 and disappeared by day 45. Daily injections of sulpiride also produced similar changes in the release of prolactin and in the replication of DNA. The growth of the anterior pituitary gland was greater in this group than in the rats which had been treated with oestradiol diundecenoate only. After the end of treatment with oestrogen and sulpiride the pituitary weight and the concentration of prolactin in the anterior pituitary gland diminished together with levels of prolactin and oestrogen in serum. There was a good correlation between weight of the gland and serum levels of prolactin. The results further support the idea of a mechanism which controls the proliferation of lactotrophs in which the release of the hormone is accompanied by an increase in pituitary DNA synthesis.

Ornithine decarboxylase activity and polyamines in the anterior pituitary gland during the rat oestrous cycle

1985 ◽  
Vol 107 (1) ◽  
pp. 83-87 ◽  
Author(s):  
L. Persson ◽  
M. Nilsson ◽  
E. Rosengren
Keyword(s):  
Pituitary Gland ◽  
Ornithine Decarboxylase ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Oestrous Cycle ◽  
Ovariectomized Rats ◽  
Oestrogen Treatment ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Releasing Hormone

ABSTRACT The biosynthesis of polyamines, an ubiquitous group of amines shown to be essential for normal cellular growth and differentiation, was studied in the rat anterior pituitary gland during the different stages of the oestrous cycle. The activity of ornithine decarboxylase (ODC), which catalyses the rate-limiting step in the biosynthesis of polyamines, was low during oestrus, metoestrus and dioestrus. However, a marked transitory rise in ODC activity was found in the pituitary gland on the evening of pro-oestrus. The rise in ODC activity was accompanied by an increase in the pituitary content of the polyamines putrescine and spermidine. Ovariectomy did not significantly change the basal ODC activity in the pituitary gland. Oestrogen treatment of ovariectomized rats resulted in a marked stimulation of pituitary polyamine biosynthesis. The largest effects were observed when oestrogen was given as two injections 72 h apart, which gave rise to levels of ODC activity comparable to those observed on the evening of pro-oestrus. The increase in polyamine synthesis in the anterior pituitary gland during pro-oestrus appeared not to be related to the preovulatory secretion of LH or prolactin, since neither LH-releasing hormone nor thyrotrophin-releasing hormone (which induces a secretion of prolactin) affected pituitary ODC activity. The observed biosynthesis of polyamines may be associated with the cellular proliferation which occurs in the anterior pituitary gland at oestrus. J. Endocr. (1985) 107, 83–87

EFFECT OF MORPHINE ON THE RELEASE OF THYROID-STIMULATING HORMONE STIMULATED BY EXPOSURE TO COLD, THYROIDECTOMY AND THE ADMINISTRATION OF THYROTROPHIN RELEASING HORMONE IN MALE RATS

1980 ◽  
Vol 86 (2) ◽  
pp. 357-362 ◽  
Author(s):  
TAKAMURA MURAKI ◽  
TERUO NAKADATE ◽  
YUKIKO TOKUNAGA ◽  
RYUICHI KATO
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inhibitory Effect ◽  
Thyroid Stimulating Hormone ◽  
Male Rats ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Exposure To Cold ◽  
Serum Tsh ◽  
Stimulating Hormone

Morphine reduced the release of thyroid-stimulating hormone (TSH) which was stimulated by exposure to cold and by thyroidectomy as well as reducing the basal level of TSH in the serum of male rats. The inhibitory effect of morphine was antagonized by naloxone which did not enhance the basal or cold-induced TSH release. Pretreatment with morphine did not reduce the release of TSH induced by exogenous thyrotrophin-releasing hormone (TRH) but enhanced it. This effect of morphine was also antagonized by naloxone. The above results suggested that the effect of morphine in reducing levels of serum TSH was not mediated by blocking the effect of TRH on the anterior pituitary gland, but that it was probably mediated by the inhibition of the release of TRH.

Thyrotrophin-releasing hormone does not accumulate glycosylated thyrotrophin, but changes heterogeneous forms of thyrotrophin within the rat anterior pituitary gland

1986 ◽  
Vol 109 (2) ◽  
pp. 227-231 ◽  
Author(s):  
M. Mori ◽  
I. Kobayashi ◽  
S. Kobayashi
Keyword(s):  
Affinity Chromatography ◽  
Pituitary Gland ◽  
Isoelectric Focusing ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Male Rats ◽  
Dependent Manner ◽  
Thyrotrophin Releasing Hormone ◽  
The Media ◽  
Dose Dependent

ABSTRACT We have investigated the effect of TRH on the accumulation of glycosylated TSH in the rat anterior pituitary gland. Hemipituitaries from adult male rats were incubated in medium containing [3H]glucosamine in the presence of TRH. [3H]Glucosamine-labelled TSH in media and pituitaries was measured by immunoprecipitation and characterized by isoelectric focusing after affinity chromatography. Incorporation of [3H]glucosamine into immunoprecipitable TSH in the media and pituitaries increased progressively with the period of incubation. Although the release of [3H]glucosamine-labelled and unlabelled TSH into media was stimulated by the addition of TRH in a time- and dose-dependent manner, TRH administration did not alter the amounts of labelled or unlabelled TSH in the anterior pituitary lobes. The anterior pituitaries were found, by isoelectric focusing analysis, to be composed of four major component peaks of [3H]glucosamine-labelled TSH. Administration of TRH caused profound changes in the radioactivity of these components and evoked new radioactive peaks, resulting in the appearance of six components in total. The present data provide evidence that TRH significantly changes the heterogeneity of glycosylated TSH in the anterior pituitary without altering the amount of the glycosylated form. J. Endocr. (1986) 109, 227–231

Dexamethasone inhibits the release of TSH from the rat anterior pituitary gland in vitro by mechanisms dependent on de novo protein synthesis and lipocortin 1

1995 ◽  
Vol 147 (3) ◽  
pp. 533-544 ◽  
Author(s):  
A D Taylor ◽  
R J Flower ◽  
J C Buckingham
Keyword(s):  
Protein Synthesis ◽  
Pituitary Gland ◽  
Outer Surface ◽  
Anterior Pituitary ◽  
De Novo ◽  
Anterior Pituitary Gland ◽  
Pronounced Increase ◽  
Pituitary Tissue ◽  
Dependent Mechanism

Abstract Glucocorticoids have been shown repeatedly to inhibit the secretion of TSH in experimental animals and in man but their site and mode of action are unknown. In the present study, we have used an in vitro model to examine the effects of dexamethasone on the resting and pharmacologically evoked secretion of TSH by the rat anterior pituitary gland, and to show how they are influenced by inhibitors of RNA/protein synthesis. In addition, we have investigated the potential role of lipocortin 1 (LC1), a protein shown previously to contribute to glucocorticoid action in several systems, as a mediator of the glucocorticoid-induced suppression of TSH release in our in vitro preparation. The significant (P<0·01) increases in the release of immunoreactive (ir)TSH from rat anterior pituitary tissue initiated by submaximal concentrations of TRH (10 nmol/l), vasoactive intestinal polypeptide (VIP, 10 nmol/l) or the adenyl cyclase activator, forskolin (100 μmol/l) were reduced significantly (P<0·05) by preincubation of the tissue with dexamethasone (0·1 μmol/l). In contrast, irTSH secretion evoked by a submaximal concentration of the L-Ca2+ channel opener BAY K8644 (10 μmol/l) was unaffected by the steroid, although readily antagonised (P<0·01) by nifedipine (1–100 μmol/l). Inclusion of actinomycin D (1·78 μmol/l) or cycloheximide (0·8 μmol/l), inhibitors of RNA and protein synthesis respectively, in the medium effectively abrogated the inhibitory effects of dexamethasone (0·1 μmol/l) on the secretory responses to TRH (10 nmol/l), VIP (10 nmol/l) and forskolin (100 μmol/l). LC1 was readily detectable by Western blotting in protein extracts of freshly excised anterior pituitary tissue. A small proportion of the protein was found to be attached to the outer surface of the cells where it was retained by a Ca2+-dependent mechanism. Exposure of the tissue to dexamethasone (0·1 μmol/l) caused a pronounced increase in the amount of cellular LC1 attached to the outer surface of the cells and a concomitant decrease in the intracellular LC1 pool. Progesterone (0·1 μmol/l) and aldosterone (0·1 μmol/l) were also weakly active in this regard, but thyroxine and tri-iodothyronine (0·1 μmol/l) were not. Addition of an N-terminal LC1 fragment, LC1(1–188) (0·05–0·53 pmol/l) to the incubation medium reduced significantly (P<0·01) the increases in irTSH release induced by TRH (10 nmol/l), VIP (10 nmol/l) and forskolin (100 μmol/l), but failed to influence (P<0·05) those initiated by BAY K8644 (10 μmol/l). Furthermore, the inhibitory actions of dexamethasone (0·1 μmol/l) on the release of irTSH provoked by TRH (10 nmol/l), VIP (10 nmol/l) and forskolin (100 μmol/l) were substantially reversed (P<0·01) by a specific monoclonal anti-LC1 antibody, while an isotype-matched control antibody was without effect. The results show clearly that dexamethasone, a semisynthetic glucocorticoid, acts at the pituitary level to inhibit the neurochemically evoked release of irTSH. They also provide novel evidence that the inhibitory actions of the steroid are dependent upon de novo RNA/protein synthesis and that they involve an LC1 dependent mechanism. Journal of Endocrinology (1995) 147, 533–544

EFFECTS OF OESTROGEN ON PITUITARY FUNCTION IN THE THYROIDECTOMIZED RAT

1965 ◽  
Vol 48 (3) ◽  
pp. 355-368 ◽  
Author(s):  
O. F. Amesbury ◽  
A. N. Contopoulos ◽  
A. A. Koneff
Keyword(s):  
Growth Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Pituitary Function ◽  
Male Rats ◽  
Typical Development ◽  
Control Groups ◽  
Pituitary Glands ◽  
Growth Promoting

ABSTRACT The effects of oestrogen administration on normal and thyroidectomized male rats were studied and compared with control groups. Determinations of trophic hormones in plasma and anterior pituitary glands were attained by bioassay procedures. In the intact rat injected with oestrogen, the growth hormone content of the anterior pituitary gland was decreased, whereas in the thyroidectomized male rats the content was elevated to levels above normal. It was found that the growth promoting potency of plasma from thyroidectomized male animals could be restored to normal levels by the administration of oestrogen. The administration of oestrogen to the thyroidectomized rat did not affect the TSH content of pituitary glands or plasma, whereas in the intact rat, resulted in a decrease in the TSH content of the pituitary gland. Administration of oestrogen decreased the gonadotrophic content of the pituitary gland in the normal and thyroidectomized rat. Pituitary glands from thyroidectomized rats injected with oestrogens showed reappearance of acidophils coupled with the typical development of post-thyroidectomy basophils.

Sign in / Sign up

Export Citation Format

Share Document