In vivo Supersensitivity of the Anterior Pituitary of Old Female Rats to Dopaminergic Inhibition of Prolactin Secretion

Gerontology ◽  
1984 ◽  
Vol 30 (6) ◽  
pp. 345-349 ◽  
Author(s):  
Daniela Cocchi ◽  
Antonello Novelli ◽  
Ilaria Ganzetti ◽  
Eugenio E. Müller
Keyword(s):  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Female Rats

Cell-density dependence of the rate of prolactin secretion from perifused rat anterior pituitary cells

1983 ◽  
Vol 97 (2) ◽  
pp. 221-228 ◽  
Author(s):  
A. M. Bentley ◽  
M. Wallis
Keyword(s):  
Density Dependence ◽  
Cell Density ◽  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Cells ◽  
The Third ◽  
Pituitary Glands ◽  
Prolactin Content ◽  
Perifusion System

Anterior pituitary glands from female rats were dispersed enzymically in the absence of dopamine. Dispersed cells (106–107) were layered onto columns containing Bio-Gel P-2 and were then perifused for 3 h with Dulbecco's Modified Eagle's Medium. The prolactin content of the perifusate and cell homogenates was determined by radioimmunoassay. Prolactin secretion during the third hour of perifusion increased as the loading of cells increased. However, the increase was not linear, and when secretion rate per 106 cells was calculated it was found that increased loading decreased the rate, which fell to a plateau of 1·3 ± 0·1 (s.e.m.) ng/min per 106 cells at a loading of about 8 × 106 cells from 3·8 ± 0·1 ng/min per 106 cells for a loading of 106 cells. This cell-density dependence of the rate of prolactin secretion in the perifusion system may be due to intercellular contact since the isolation of the tissue removes the influence of hypothalamic factors, while localized build up of prolactin (potentially causing direct autoregulation on the lactotroph) seems unlikely because of the continuous flow of medium.

REGULATION OF THE METABOLISM OF PITUITARY NUCLEIC ACIDS IN FEMALE RATS

1980 ◽  
Vol 85 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. BÍRÓ
Keyword(s):  
Nucleic Acids ◽  
Intraperitoneal Injection ◽  
Anterior Pituitary ◽  
Rna Metabolism ◽  
Female Rats ◽  
Biphasic Effect ◽  
Lh Rh ◽  
Lh Releasing Hormone

SUMMARY Ovariectomy caused an increase in the metabolism of pituitary nucleic acids. This effect was reversed in vivo by a biphasic action of oestradiol-17β which first facilitated RNA metabolism after 8 h and then inhibited it 16 h after intraperitoneal injection. To analyse the origin of this biphasic effect the roles of LH releasing hormone (LH-RH) and hysterectomy were examined. Incorporation of uridine into the RNA of the anterior pituitary gland of female rats was inhibited both in vivo and in vitro by LH-RH. Hysterectomy augmented the increase in the RNA metabolism caused by ovariectomy whereas steroid-free uterine extracts inhibited the increase significantly. We have concluded that extrapituitary factors may be involved in the effects of oestrogen on the metabolism of pituitary nucleic acids.

scholarly journals Effects of long-term treatment with resveratrol and subcutaneous and oral estradiol administration on pituitary function in rats

2006 ◽  
Vol 189 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Martina Böttner ◽  
Julie Christoffel ◽  
Hubertus Jarry ◽  
Wolfgang Wuttke
Keyword(s):  
Serum Levels ◽  
Term Treatment ◽  
Prolactin Secretion ◽  
Gnrh Receptor ◽  
Female Rats ◽  
Pituitary Function ◽  
Ovx Rats ◽  
Long Term Treatment

Hormone replacement therapy (HRT) has been used for several decades to treat menopausal discomforts. However, in the light of recent studies that draw attention to the potential hazards of conventional HRT, various attempts have been undertaken to search for alternatives to classical HRT. Phytoestrogens are claimed to be capable of positively influencing menopausal symptoms, including hot flushes. We designed a long-term study of 3 months to assess the effects of subcutaneous and orally fed 17β-estradiol (E2), as well as the actions of resveratrol (RES) on pituitary function in female rats. Our results have demonstrated that RES binds with a 10-fold lower affinity to estrogen receptor (ER)-α than to ERβ. The data from the in vivo study revealed that a dosage of 5 μg and 50 μg RES/kg bodyweight per day given to ovariectomized (OVX) rats achieved serum levels of 1.0 and 8.1 μM respectively. Long-term treatment of OVX rats with RES revealed no estrogenic potential on pituitary function in vivo as assessed by LH and prolactin secretion and by regulation of mRNAs for LHα, LHβ, and GnRH receptor. Subcutaneous treatment with E2 in silastic capsules exerted stronger effects on LH and prolactin secretion, as well as on LHβ, LHα, GnRH receptor, and ERβ mRNA regulation compared with orally applied estradiol benzoate despite comparable serum levels. Levels of aryl hydrocarbon receptor (AhR) mRNA in the pituitary were increased following OVX and attenuated by long-term E2 treatment, whereas RES did not modulate AhR mRNA expression.

Rat anterior pituitary neuropeptides following chronic prolactin manipulation: a combined radioimmunoassay and mRNA study

1991 ◽  
Vol 131 (3) ◽  
pp. 411-419 ◽  
Author(s):  
D. J. O'Halloran ◽  
P. M. Jones ◽  
M. A. Ghatei ◽  
S. R. Bloom
Keyword(s):  
Anterior Pituitary ◽  
Qualitative Change ◽  
Prolactin Secretion ◽  
Mrna Levels ◽  
Female Rat ◽  
Concurrent Treatment ◽  
Oestrogen Treatment ◽  
Mrna Analysis ◽  
Haloperidol Treatment

ABSTRACT Prolactin secretion is highly regulable, and the possibility exists that there are local intrapituitary factors controlling prolactin secretion. Recently, the neuropeptides vasoactive intestinal peptide (VIP), galanin and substance P (SP) have been co-localized to the lactotroph in the female rat. We investigated the effects of alterations in prolactin status in vivo on pituitary and hypothalamic expression of these peptides by specific radioimmunoassays and mRNA analysis. In the anterior pituitary, following haloperidol treatment, the contents of both VIP and galanin were suppressed to below detectable levels. Similarly, after bromocriptine treatment, the content of VIP was decreased to below the detection limit of the assay while galanin (14·2±1·3 vs control 21·0±2·1 fmol/mg, P < 0·05) also showed a significant reduction. The levels of VIP mRNA and galanin mRNA in these groups showed the same qualitative change as their respective peptides. Concurrent treatment with highdose oestrogen modified the VIP peptide response to bromocriptine (1368·7 ±149·2 vs bromocriptine 843·4±82·7 fmol/mg, P<0·05) but not to haloperidol. Oestrogen-induced decreases in galanin content were not influenced by either treatment. The pituitary content of SP showed a fall after oestrogen treatment (1·1±0·01 vs control 6·4±0·8 fmol/mg, P<0·05) which was not significantly altered by either bromocriptine or haloperidol. Likewise, SP mRNA levels in the pituitary were decreased by 90% following oestrogen treatment. Hypothalamic expression of these peptides did not change with any of the treatments. This study demonstrates the tissue and peptide specific influences of prolactin status in regulating anterior pituitary VIP, galanin and SP at the pretranslational level. The results of this study suggest that prolactin status and/or dopaminergic influences are important in the regulation of anterior pituitary neuropeptides. Journal of Endocrinology (1991) 131, 411–419

Heme Oxygenase in the Rat Anterior Pituitary: Immunohistochemical Localization and Possible Role in Gonadotropin and Prolactin Secretion

2003 ◽  
Vol 228 (1) ◽  
pp. 64-69 ◽  
Author(s):  
Iulia C. Alexandreanu ◽  
David M. Lawson
Keyword(s):  
Heme Oxygenase ◽  
Anterior Pituitary ◽  
Immunohistochemical Localization ◽  
Prolactin Secretion ◽  
Pituitary Cells ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Lh Release

The objectives of this study were to determine if heme oxygenase (HO), which catalyzes the degradation of heme and the formation of carbon monoxide (CO), is localized in the rat anterior pituitary and, if so, to determine if hemin (a substrate for HO) or chromium mesoporphyrin (CrMP) (an inhibitor of HO), alter pituitary gonadotropin and prolactin secretion. For localization of HO, sections of anterior pituitaries obtained from mature Holtzman Sprague-Dawley rats in different stages of the estrous cycle were immunostained for two of the HO isoforms, HO-1 and HO-2. The immunostaining for the inducible HO isoform (HO-1) was limited to discrete populations of pituitary cells, whereas the constitutive isoform (HO-2) had a more widespread distribution. The afternoon surge of leutinizing hormone (LH) in the plasma of ovariectomized, estradiol-treated rats was advanced by 2 hr after 7 days of treatment with CrMP (4 μM/kg), and this effect was reversed when hemin (30 μM/kg) was coadministered with CrMP. The afternoon follicle-stimulating hormone (FSH) surge was not affected by either treatment. In contrast, the afternoon prolactin (PRL) surge was completely blocked or delayed by CrMP treatment, and this effect was not reversed by hemin. In vitro perifusion of pituitary explants with CrMP also significantly reduced PRL release compared with secretion from untreated explants. In vitro gonadotropin-releasing hormone (GnRH)-stimulated FSH secretion was significantly increased from pituitary explants of ovariectomized, estradiol-treated rats treated in vivo with hemin but was unaffected by CrMP treatment, whereas GnRH-stimulated LH release was not affected by hemin but was increased by CrMP treatment. In conclusion, this study demonstrates that HO exists in the rat anterior pituitary gland, and that a substrate and an inhibitor of this enzyme alter the secretion of gonadotropins and PRL.

THE INTRACELLULAR LOCALIZATION OF OESTROGEN IN RAT TISSUES

1965 ◽  
Vol 32 (1) ◽  
pp. 9-15 ◽  
Author(s):  
R. J. B. KING ◽  
J. GORDON ◽  
D. R. INMAN
Keyword(s):  
Anterior Pituitary ◽  
Soluble Fraction ◽  
Intracellular Localization ◽  
Female Rats ◽  
Radioactive Material ◽  
Rat Tissues ◽  
Nuclear Fraction ◽  
Cell Fractionation ◽  
Rat Pituitary

SUMMARY The radioactive material in rat pituitary, liver and uterus 1 hr. after the s.c. injection of either 0·73 or 7·3 μg. [6,7-3H]oestradiol has been investigated. Oestrone and oestradiol were the only compounds detected in pituitary and uterus whereas at least six compounds were present in liver. Cell fractionation studies have been carried out on anterior pituitary and liver from female rats which had received an injection of either 0·73 or 7·3 μg. [6,7-3H]oestradiol in vivo. Most of the tritium in the anterior pituitary was associated with the nuclear fraction whereas most of the tritium in the liver was in the soluble fraction. The uptake of [6,7-3H]oestradiol by the anterior pituitary reached a maximum ½-1 hr. after injection of the steroid and remained at this level for the next 3 hr. The intracellular distribution of this steroid at different times after injection suggests that the steroid passes into the cytoplasm and then into the nucleus.

Size heterogeneity of prolactin secreted from and stored in the rat anterior pituitary gland in vitro

1984 ◽  
Vol 4 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Andrew M. Bentley ◽  
Teresa K. Surowy ◽  
Michael Wallis
Keyword(s):  
Anterior Pituitary ◽  
Relative Proportion ◽  
Gel Filtration ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Glands ◽  
Dimeric Form ◽  
Size Heterogeneity ◽  
Pituitary Prolactin

The size heterogeneity of rat pituitary prolactin was investigated using anterior pituitary glands from female rats incubated in vitro and gel filtration on Sephadex G-100. Monomeric prolactin was preferentially secreted compared with dimeric and ‘trimeric” material. When glands were incubated with dopamine, prolactin secretion was inhibited and the relative proportion of dimer in the gland (but not the medium) was decreased. Morphine sulphate reversed the effect of dopamine on prolactin secretion and on the proportion of prolactin in the gland that was in the dimeric form. The results suggest that monomeric prolactin is more readily secreted than dimer, and that dopamine decreases the production or stability of the dimer.

Excess in vitro prolactin secretion by pituitary cells from ovariectomized old rats

1984 ◽  
Vol 247 (4) ◽  
pp. E483-E488
Author(s):  
M. Haji ◽  
G. S. Roth ◽  
M. R. Blackman
Keyword(s):  
In Vitro Release ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Pituitary Cells ◽  
Lh Release ◽  
Old Rats

Various in vivo and in vitro pituitary lactotropic and gonadotropic functions were measured in mature (6-7 mo, normally cycling) and old (24 mo, constant diestrus) female Wistar rats. Serum prolactin (PRL) levels were higher (P less than 0.001), whereas luteinizing hormone (LH) values were similar (P greater than 0.05) in old versus mature rats both before and 3 days after ovariectomy. Serum PRL levels decreased significantly (P less than 0.005) postovariectomy only in the mature rats. The in vitro release of PRL and LH was measured for 4 days in primary adenohypophyseal cell cultures from the ovariectomized rats. Both basal and 17 beta-estradiol (E2)-stimulated PRL release (P less than 0.001) and production (P less than 0.005) were greater by cells from old rats. In contrast, both basal release and E2-stimulated LH release were greater (P less than 0.001) by cells from mature rats. Peak PRL release by cells from both old and mature rats occurred after exposure to E2 doses 1/100th of those required for peak LH release. These data support the hypothesis that intrinsic derangements in anterior pituitary function contribute to the reproductive decline in aging female rats and that different pituitary cell types exhibit discordant age changes in estrogenic sensitivity.

Possible role of dopamine and noradrenaline in the regulation of prolactin secretion from an ectopic anterior pituitary gland in female rats

1987 ◽  
Vol 113 (1) ◽  
pp. 45-49 ◽  
Author(s):  
J. J. Fernández-Ruiz ◽  
M. Cebeira ◽  
C. Agrasal ◽  
J. A. F. Tresguerres ◽  
A. Bartke ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Plasma Prolactin ◽  
Noradrenaline Content ◽  
Pituitary Tissue ◽  
Dopamine Content ◽  
And Control

ABSTRACT It was recently reported that anterior pituitary tissue transplanted to an ectopic site contains measurable amounts of dopamine and noradrenaline. To examine the possibility of local catecholaminergic control of prolactin secretion from ectopic pituitaries, pituitary grafted and sham-operated female rats were submitted to several pharmacological treatments modifying catecholamine synthesis. Administration of a single dose of α-methyl-p-tyrosine (α-MPT) significantly reduced dopamine content in the graft, while noradrenaline content was not modified. Similar changes in the contents of dopamine and noradrenaline after α-MPT administration were observed in the hypothalamus and in the in-situ pituitary in both grafted and sham-operated rats. Plasma concentrations of prolactin were increased in both grafted and sham-operated rats after administration of α-MPT. A single injection of l-3,4-dihydroxyphenylalanine (l-DOPA) increased dopamine content in the ectopic pituitary gland without altering the noradrenaline content, and produced similar effects in the hypothalamus and in-situ pituitary of grafted and control rats. Plasma prolactin concentrations were decreased by l-DOPA in both pituitary grafted and control rats. Administration of dl-treo-dihydroxyphenylserine (DOPS) increased noradrenaline content in the ectopic pituitary and reduced plasma prolactin concentrations in pituitary grafted rats. In contrast, injection of DOPS to control rats increased both hypothalamic noradrenaline content and plasma prolactin concentrations. These results suggest that dopamine and noradrenaline present in the ectopic pituitary tissue have a role in mediating prolactin release from pituitary transplants. J. Endocr. (1987) 113, 45–49

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