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At least 163 records · Page 9Linked to original sources

PubMed1991

Prolactin receptor gene expression in the rabbit: identification, characterization and tissue distribution of several prolactin receptor messenger RNAs encoding a unique precursor.

The expression of the prolactin (PRL) receptor gene was studied in rabbit tissues by Northern blot and S1 mapping analysis of mRNA preparations. Rabbit mammary gland contained three major (10.5, 3.4, and 2.7 kb) and one minor (6.2 kb) prolactin receptor poly(A)+ RNA transcripts all of which contain the entire coding sequence of the long form of PRL receptor. Each of these mammary mRNAs hybridized equally well with cDNA sequences encoding either the NH2 terminal, middle, or COOH terminal part of the rabbit mammary PRL receptor. The four mRNAs differed only in their 5'- and 3'-untranslated regions. The 10.5 kb mammary transcript was further shown to represent a primary transcript of nuclear origin. Among the various rabbit tissues tested, male and female adrenals, mammary gland, ovaries, and jejunum contained the highest level of prolactin receptor mRNA. The prolactin receptor gene was also expressed at moderate to weak abundance in uterus, liver, kidney, pancreas, testis and seminal vesicles. No prolactin receptor mRNA species were detected in adult muscle, lung, total brain, placental cotyledons and spleen, and in thymus from young animals. In all the rabbit tissues examined, the same four PRL receptor poly(A)+ RNA transcripts identified in the mammary gland were expressed and no additional transcript(s) were detected. Variations in the relative proportion of the 10.5 kb transcript and the two smaller transcripts were observed, while the ratio of the 3.4 and 2.7 kb mRNAs remained unchanged. These findings ask for the role of these different transcripts generated in the rabbit, all of which encode the same long form of PRL receptor precursor but have heterogenous 5'- and 3'-untranslated regions. Moreover, they suggest that the various forms of PRL receptor mRNA originate through differential splicing of a single PRL receptor gene.

Animals↗

PubMed1989

Altered gonadotropin and prolactin release induced by median eminence (ME) lesions and pharmacological manipulation of prolactin release: further evidence for separate hypothalamic control of FSH and LH release.

To delineate more clearly the regions of the median eminence involved in the control of gonadotropin secretion, electrolytic lesions were made in the median eminence of adult male rats. Also the role of prolactin in the maintenance of gonadotropin secretion and sex organs was further evaluated by the administration of alpha-bromo-ergocryptine (CB154) or its diluent SC to lower prolactin via its dopamine agonist action in these animals with lesions. The effects of elevation of prolactin by the administration in the drinking water of the dopamine antagonist, sulpiride, were also evaluated in intact rats. At the conclusion of the experiments the localization of lesions was carefully evaluated by microscopic examination of serial sections through the hypothalamic region. The results indicate that lesions which completely destroyed the median eminence led to elevation in plasma prolactin and profound decreases in plasma FSH and LH associated with atrophy of testes and accessory sex organs. This result was not affected if CB154 was given to lower the elevated prolactin levels. Lesions which destroyed the rostral 2/3 of the median eminence were frequently associated with declines in plasma LH and relatively normal plasma FSH, whereas lesions which extended caudally to destroy the posterior median eminence were associated uniformly with a profound lowering of FSH. If these lesions did not include the anterior portions of the median eminence. LH levels remained normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Prolactin-releasing peptide is essential to maintain the prolactin level and osmotic balance in freshwater teleost fish.

We administered prolactin-releasing peptide (PrRP) or anti-PrRP antiserum to goldfish in fresh water and analyzed their effects on prolactin and osmoregulatory mechanisms. The pituitary mRNA level of prolactin increased by PrRP but decreased by anti-PrRP. The rate of water inflow in the gills decreased by PrRP and increased by anti-PrRP, showing that PrRP restricts branchial water permeability, as also restricted by prolactin. PrRP also expanded the mucous cell layers on the scales, which may restrict efficiently water inflow by the mucous system. Eventually, the plasma osmotic pressure decreased by anti-PrRP. We conclude that PrRP is essential to maintain prolactin levels and osmotic balance in fresh water.

Animals↗

PubMed2004

Growth hormone, cortisol and prolactin responses to physical exercise: higher prolactin response in depressed patients.

This study was designed to compare growth hormone, cortisol and prolactin responses to physical exercise in depressed patients and healthy comparison subjects. Patients fulfilled the DSM-IV diagnostic criteria for current major depressive disorder; subjective depressive symptoms were rated with Montgomery-Asberg Depression Rating Scale (MADRS) immediately before the experiment. Growth hormone, cortisol and prolactin were measured before and immediately after physiologically stressful bicycle cardiopulmonary exercise test. After exercise, there were three additional hormone measurements, with 30-min intervals. No significant difference was found in baseline growth hormone, cortisol or prolactin levels between patients and the control group. Plasma growth hormone and cortisol levels increased significantly during physical exercise in both patients and controls and returned to baseline in 90 min. There was no significant difference in growth hormone or cortisol responses to physical exercise between the two groups. However, prolactin levels increased only in the depressed patients group during the exercise. We hypothesize that acute exercise may have a stronger effect on serotonin (5-HT) release in depressed patients, which is reflected in increased plasma prolactin concentration.

Adult↗

PubMed2000

Does prolactin releasing peptide receptor regulate prolactin-secretion in human pituitary adenomas?

Prolactin-releasing peptide (PrRP) and its receptor (PrRP-R) have recently been characterized and cloned. PrRP functions as a prolactin-secreting factor through binding with PrRP-R, which is extensively expressed in the human pituitary. We studied the expression of PrRP-R in human pituitary adenomas. Pituitary adenomas were collected from 13 patients by transsphenoidal resection. Six patients had prolactin-secreting adenomas, three had adrenocorticotropic hormone-secreting adenomas, one had a growth hormone -secreting adenoma, and three had non-secreting adenomas. All pituitary adenomas examined by reverse transcription-polymerase chain reaction analysis expressed PrRP-R. When semiquantitative competitive PCR was performed to determine the relative amounts of the PrRP-R mRNA expression level, there was no correlation between plasma prolactin levels and PrRP-R expression levels. These results suggest that the plasma prolactin level is regulated by means other than signal transduction through PrRP-R activation.

Adrenocorticotropic Hormone↗

PubMed1998

Increased body weight associated with prolactin secreting pituitary adenomas: weight loss with normalization of prolactin levels.

OBJECTIVE: Hyperprolactinaemia in humans may be associated with a high prevalence of obesity but the nature of this link is poorly defined. The aim of this study was to establish the relationship between hyperprolactinaemia and body weight in patients with prolactin-secreting pituitary tumours. DESIGN: We conducted a retrospective study of prolactinoma patients treated at the Endocrine Institute of the Tel Aviv Medical Center, Israel, during the period 1989-1996. Patients with clinically non-functioning pituitary macroadenomas (NFA) served as the control group. Data on demographic parameters, body weight before and during treatment, clinical presentation including history of weight fluctuations, tumour size as measured by computed tomography or magnetic resonance imaging, modalities and response to treatment, and pituitary function before and during treatment were recorded from medical files. PATIENTS: Forty-two patients with prolactinomas (PR) and 36 patients with clinically non-functioning macroadenomas (NFA) comprised the study population. RESULTS: Mean weight was 93 +/- 3.4 kg and 78 +/- 2.7 kg in male patients with PR and NFA respectively (P = 0.0007). Recent weight gain (8 to 22 kg) was a presenting symptom in 13 PR patients, whereas only one NFA patient had this clinical presentation (P = 0.001). Seventeen PR patients lost weight (mean change -8.3 +/- 1.5 kg, range -2-28 kg), during prolactin lowering therapy, 11 of whom had entirely normalized prolactin levels. Fourteen of the 18 patients who did not lose weight still had elevated prolactin levels (P = 0.01). Weight loss in patients with PR could not be attributed to altered pituitary function nor to compression of the third ventricle. In contrast to PR, no significant weight loss was observed in NFA patients. CONCLUSION: Weight gain and elevated body weight are frequently associated with prolactinomas regardless of a mass effect on the hypothalamus or pituitary function. In this series, weight loss was recorded in 70% of prolactinomas patients and in 90% of male patients who normalized their prolactin levels. We propose the inclusion of hyperprolactinaemia in the differential diagnosis of endocrine obesity and weight gain.

Adult↗

PubMed1981

Serum prolactin levels and immunohistochemical localization of prolactin in trophoblastic disease.

The circulating levels of chorionic gonadotropin, pregnancy specific beta-I-glycoprotein, prolactin and oestradiol were estimated by radioimmunoassay in 219 serum samples from 18 patients with choriocarcinoma and 45 samples from 8 patients with hydatidiform mole. Prolactin and oestradiol concentrations were higher in samples which also contained trophoblastic markers. This difference was also seen in patients with choriocarcinoma and it was not due to chemotherapy, since the difference between hCG positive and hCG negative samples was maintained during chemotherapy. Prolactin was found by immunoperoxidase technique in the syncytiotrophoblast of normal placenta throughout gestation, and also in hydatidiform mole, invasive mole and choriocarcinoma. It is suggested that the malignant syncytiotrophoblast may contribute to circulating prolactin levels either by direct secretion of prolactin or by oestrogen stimulation of the pituitary.

Chorionic Gonadotropin↗

PubMed2004

Human prolactin receptor variants in breast cancer: low ratio of short forms to the long-form human prolactin receptor associated with mammary carcinoma.

Prolactin plays an essential role in the development of rodent mammary tumors and is a potent mitogen in human normal and cancerous breast tissues/cells. In this study, we have analyzed the expression of prolactin receptors, including the long receptor form (LF; stimulatory) and two novel short forms (SFs; S1a and S1b) derived from alternative splicing that are inhibitory of the activation induced by prolactin through the LF. Southern analysis of breast cancer profiling arrays revealed that 29 patients (group I) expressed an elevated LF, 10 patients (group II) showed decreased LF, and 8 patients (group III) had no change relative to the adjacent normal tissue. Their respective SF expression was increased in 21 patients of group I and generally decreased in groups II and III. However, the ratio of SF to LF was significantly decreased in 76% of the breast tumors and distributed evenly among the groups. Quantification of differential expression of prolactin receptor variants by real-time PCR in 15 pairs of human normal and tumor breast-matched tissues revealed a similar significant decrease in the ratio of SF to LF in the tumor tissue. Consistent lower ratio of SFs to LFs was confirmed in 8 of ten different breast cancer cell lines compared with normal mammary Hs578Bst and MCF10A cells. Because SFs act as dominant negative regulators of the stimulatory actions of the LF in vitro, their relatively reduced expression in cancer could cause gradations of unopposed prolactin-mediated LF stimulatory function and contribute to breast tumor development/progression.

Blotting, Southern↗

PubMed1981

Restoration of pituitary prolactin synthesis and release by the administration of morphine to rats bearing a transplanted prolactin-secreting tumor.

Rats bearing transplanted prolactin-secreting tumors are known to have very high prolactin levels in the serum, reduced hypothalamic opiate concentrations, increasing hypothalamic dopamine synthesis and increased hypophyseal portal blood dopamine levels. Further, it has been shown that incubation in 3H-leucine of anterior pituitary glands from these tumor-bearing rats demonstrates a marked inhibition of 3H-prolactin synthesis and release. Using rats with the prolactin-secreting tumor MtTW15, we have found that 4 days of continuous administration of either morphine sulfate 1.44 mg daily or haloperidol 0.11 mg daily using and osmotic infusion pump caused a significant increase in the synthesis and release of 3H-prolactin from incubated pituitary gland compared to untreated tumor-bearing animals. Morphine may reduce hypothalamic dopamine release, whereas haloperidol is a direct dopamine receptor antagonist in achieving these effects.

Animals↗

PubMed1985

Dopamine-induced physical barrier to inhibit prolactin release in mammotrophs disappears during resumption of prolactin secretion.

After finding that dopamine can cause extensive changes in mammotroph ultrastructure within 2 min of administration, we further examined mammotrophs 20 and 40 min after dopamine injection when prolactin secretion had resumed. Dopamine (1,000 micrograms/kg) was injected into the right atrium of estradiol-primed male rats through indwelling cannulae. Rats were killed by decapitation 2, 20 and 40 min after dopamine treatment and their pituitaries were processed for electron microscopy. Within 2 min of administration, dopamine completely stopped prolactin release and significant changes in mammotroph ultrastructure were observed: peripheral relocation of rough endoplasmic reticulum (RER) ('dopamine barrier'); fewer secretory granules in close proximity to the cell membrane; fewer exocytoses, and increased numbers of 'intracellular bodies' associated with secretory granules (putative granule disposal system). 20 min following dopamine administration, when prolactin secretion had resumed, there appeared to be a breaking up of the 'RER barrier' in that more vesicular elements were seen and the amount of peripheral RER was reduced; more granules were adjacent to the cell membrane and exocytotic figures were more numerous. 'Intracellular bodies' decreased in number. By 40 min, mammotrophs appeared to resemble those of estradiol-primed controls with the RER stacked to one side of the cell and small numbers of 'intracellular bodies'. The correlation between ultrastructural changes in mammotrophs and prolactin release implies that the 'RER barrier' is part of a mechanism by which prolactin release is inhibited.

Animals↗

PubMed1980

Possible role of prolactin and pineal prolactin-regulating substances in pineal-mediated gonadal atrophy in hamsters.

Homoplastic anterior pituitaries were transplanted beneath the renal capsule of adult male, Syrian golden hamsters and the effects studied on the gonadal and accessory organ atrophy following bilateral optic enucleation or placement in reduced (L/D = 10/14 h) photoperiods. In all cases, control hamsters, bearing kidney fragments transplanted beneath their renal capsules, showed gonadal atrophy and reduced blood levels of prolactin and LH at 8--10 weeks following light deprivation. On the other hand, hamsters, bearing three or four homoplastic pituitary grafts, showed complete maintenance of gonadal and accessory weights as well as normal or supranormal serum prolactin levels. Prolactin, but not LH, levels were maintained in hypophysectomized male hamsters bearing pituitary homografts. These results point out the significant role played by prolactin, and possibly that of pineal prolactin-regulating factors, in pineal-mediated gonadal atrophy.

Animals↗

PubMed2005

Mechanism of adrenomedullin-induced prolactin release from human prolactin-releasing adenoma cells.

The mechanism of adrenomedullin-induced prolactin release was investigated in prolactin-secreting human pituitary adenoma cells by intracellular calcium measurement and static incubation study. Adrenomedullin stimulated prolactin release in a concentration-dependent manner. The stimulation was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated adrenomedullin-induced prolactin release. The mechanism of adrenomedullin action was studied by fura 2-based intracellular calcium measurement. Adrenomedullin increased intracellular calcium concentration in these cells. The increase was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated the calcium response. These data indicate that adrenomedullin stimulates prolactin release by modulating calcium influx through voltage-gated calcium channels dependently on extracellular sodium. Mechanisms involving sodium-influx mediated depolarization may play a role in the stimulatory action.

Adrenomedullin↗

PubMed1990

Seasonal variations in prolactin, growth hormone and thyroid hormones and the prolactin surge at ovulation do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season.

Injection of bromocriptine from 5 days before until 5 days after mating clearly suppressed the periovulatory prolactin surge in ewes in the anoestrous and oestrous season but did not change the litter size significantly. Progesterone, GH, TSH or thyroid hormone concentrations were not influenced by the bromocriptine treatment. The progesterone concentrations were lower during the first weeks after mating in the anoestrous season compared to the oestrous season, while there was no difference between pregnant and non-pregnant ewes. During later gestation this seasonal difference was only observed in the non-pregnant ewes. At the same time there was a clear difference between pregnancy and non-pregnancy in both seasons. The prolactin, GH and thyroid hormone values also varied significantly during gestation. Since these patterns are identical in pregnant and non-pregnant ewes, the fluctuations are due to environmental factors and not to pregnancy or altered progesterone concentrations. In the anoestrous season prolactin, GH, T4 and T3 levels were higher than in the breeding season, while rT3 showed the opposite pattern. The TSH concentration did not differ between the two seasons. These results suggest that seasonal variations in prolactin, GH and thyroid hormones or the periovulatory prolactin surge do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season.

Animals↗

PubMed1979

International Reference Preparation of human prolactin for immunoassay: definition of the International Unit, report of a collaborative study and comparison of estimates of human prolactin made in various laboratories.

As authorized by the World Health Organization 29th Expert Committee on Biological Standardization, the preparation of human prolactin in ampoules coded 75/504 has been established as the International Reference Preparation (IRP) of human prolactin for immunoassay. From the results of a collaborative study, to which 15 laboratories in nine countries contributed, with the agreement of the participants, the content of each ampoule is defined as 0.650 International Units (i.u.; 650 mi.u.) immunoassay. The results of this collaborative study show that the IRP is adequately stable and suitable for use as a standard for the determination of prolactin in human plasma and serum. Estimates of the prolactin content of human plasma and serum made in the various laboratories have been compared and show good agreement in ranking order, but only fair agreement in the numerical value of the estimates. Numerical agreement is poor between estimates of the human prolactin content of two samples identical except for coding; this shows the difficulty in achieving continuity of estimates when any laboratory calibrates a replacement standard.

Female↗

PubMed1987

Monoclonal antibodies against human, bovine and rat prolactin: epitope mapping of human prolactin and development of a two-site immunoradiometric assay.

Nine mouse hybridoma cell lines producing monoclonal antibodies (MCA) against human prolactin (hPRL), 19 cell lines against bovine prolactin (bPRL) and one MCA against rat prolactin (rPRL) were established. The MCA were characterized by one- and two-site radioimmunoassays (RIA) as well as indirect immunofluorescence (IIF) and used for epitope mapping of hPRL and immunoradiometric assays (IRMA). Interspecies cross-reactivity studies by RIA revealed two groups of anti-hPRL MCA: seven which reacted only with hPRL and two additionally recognizing bPRL and ovine prolactin (oPRL). The anti-bPRL MCA, which were tested on pituitary sections by IIF could be divided into 17 MCA cross-reacting with the closely related oPRL, and two MCA which showed additional cross-reactions with equine prolactin. The anti-rPRL antibody reacted exclusively with rPRL in direct binding RIA studies. No intraspecies cross-reactions with the closely related protein hormones placental lactogen and GH were detected. To elucidate the antigenic surface of hPRL all MCA directed against hPRL were then used for two-site epitope mapping studies in which pairs of MCA were assessed for simultaneous reaction with the same antigen. The native hormone was incubated with the first, solid-phase bound, so called 'capture MCA', and this complex treated with a second, 125I-labelled 'detection MCA'. Based on the results of these combinations, at least three sterically non-overlapping and (taking RIA cross-reaction studies into consideration) two additional epitopes could be defined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Differential dopamine-induced prolactin mRNA levels in various prolactin-secreting cell (sub)populations.

We have examined the effects of dopamine on prolactin gene expression using quantitative in-situ hybridization histochemistry in different pituitary cell (sub)populations separated according to their density on a discontinuous Percoll gradient. Administration of dopamine resulted in a drastic reduction in hybridization of 35S-labelled DNA probe complementary to prolactin mRNA in total pituitary cells and in lactotrophs with low density. In contrast, dopamine significantly stimulated mRNA accumulation in prolactin-secreting cells with high density compared with other cell layers. The combined use of Percoll gradient and quantitative in-situ hybridization is a valuable and sensitive method with which to examine prolactin-secreting cell response to a given stimulation. Prolactin-secreting cells with high and low density clearly show functional heterogeneity in their response to dopamine.

Animals↗

PubMed1984

[Multiple forms of hypophyseal prolactin. A new glycosylated form of prolactin with increased biological activity].

Different forms of prolactin obtained from porcine hypophysis and differing in terms of molecular weight, electrophoretic mobility and biological activity were studied by polyacrylamide gel electrophoresis. A glycosylated form of prolactin with Mr 25 000 and possessing an increased biological activity towards pigeon crop was revealed. It was found that the carbohydrate component of this prolactin form is attached to asparagine at position 31; no differences were revealed between the amino acid composition of the major and glycosylated forms of the hormone. In the hypophysis, the glycosylated form content makes up to 30-40% of the total prolactin monomer content. A disulfide dimeric form of prolactin with Mr of about 50 000 was isolated and characterized.

Amino Acids↗

PubMed1995

Effects of norethisterone acetate and tamoxifen on serum prolactin levels, uterine growth and on the presence of uterine immunoreactive prolactin in estradiol-treated ovariectomized rats.

The aim of the present work was to study the effects of the antiestrogen tamoxifen (TAM), of progestin norethisterone acetate (NA) and of their combination on serum prolactin levels, uterine growth and the presence of uterine immunoreactive prolactin in estradiol-treated rats. Ovariectomized female Wistar rats were injected sc with estradiol valerate (VE, 50 micrograms/rat per week) or oil vehicle. During the second week, estradiol-treated rats also received NA (0.12 or 1.0 mg/rat, sc, daily) or TAM (0.06 mg/rat) alone or in combination with NA (0.12 mg). Serum prolactin levels were suppressed to the same extent in the TAM- and 1.0 mg NA-treated groups compared with rats given estrogen alone (2.3 +/- 0.3 and 5.6 +/- 1.5 ng/ml for TAM and NA groups vs 39.7 +/- 3.6 ng/ml for VE groups, P < 0.05). Except for the lowest dose of NA, uterine wet weight and DNA content were significantly reduced in all groups compared to estradiol alone (236.8 +/- 18.0 and 295.6 +/- 27.8 mg vs 309.4 +/- 32.2 mg for uterine weight in TAM and NA groups vs VE, respectively, P < 0.05; and 1.14 +/- 0.05 and 0.93 +/- 0.04 mg/uterus vs 1.33 +/- 0.06 mg/uterus for uterine DNA in TAM and NA groups vs VE groups). The combination of NA and TAM resulted in a higher degree of suppression of uterine growth than when each drug was used alone, indicating an additive antiproliferative effect of NA and TAM. Although no prolactin immunostaining was detected in the uterus of rats treated with estradiol, uterine immunoreactive prolactin was identified in those treated with NA, TAM or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗